# A way of getting the water to the top of the tall building without electricity?

First, let me explain the situation. Post-apocalypse setting, a group of humans (let's say around a hundred of them) have to find safe places to live at, protected from animals, bandits, and other menaces. They decided on a group of tall buildings (as in the picture), between 12 and 18 stories high. They live on top of them, last few floors. It provides safety, overlook of the surroundings.

Now, the city is ruined so there is no running water in the waterworks, but, there is a strong spring and a well in between the buildings. There is no city wide electrical grid, and they use generators (but rarely due to fuel consumption) and solar panels, but those are usually spent on lights, preparing food, refrigerators, etc.

Idea is that on the top of the building they have greenhouses to grow veggies for their use. But, veggies and greenhouses need water. And I don't think that rainwater is enough, even if collected for that purpose.

So, the question is, how to get the water from the spring or the well to the top of the building, where, for example, could be a big water reservoir? Or is it somehow possible to hook and reconnect the water pipes of the buildings to the spring instead of city waterworks and get it directly to the faucets?

Several members of the population living there have some knowledge in engineering and construction, theoretical and practical, so it can be done if it doesn't include some ultra complicated work that require some special machinery or conditions.

Is it possible at all without electricity and pumps? If not, I am open to all kinds of suggestions!

• You need to research siege tactics. A castle (that's what each of your towers is) with the water supply outside the walls is a serious risk. – RonJohn Mar 5 '18 at 20:11
• How will you get all of the soil up there? You're gonna need at least 500 square meters per person to be able to grow enough food to survive, which is at minimum at least 200 metric tons of soil. Aside from the time it would take to move it by hand, that's going to require a huge amount - years worth - of food due to the extra caloric expenditure from carrying it up the stairs. Sure, once you've got it up there, you can compost to create more, but every pound of compostable material you grow is a pound of food you could've grown, so then you'll need even more farmland. – AJMansfield Mar 5 '18 at 20:15
• ˇ@AJMansfield This is just a part of their diet, the greenhouse vegetables. Trade, hunting, scavenging and planting in area between the buildings is the rest. Ive done research of the minimum and maximum of yield in greenhouses and so on. At the moment the water is the issue, actually the transport of it, hence the questions. – Bora Mar 5 '18 at 20:31
• Wait, are you seriously asking how you can generate mechanical energy next to a strong running spring? – Kevin Mar 6 '18 at 4:16
• Just handwave "collecting rainwater" as being sufficient (which it honestly could be depending on the weather) - it wouldn't be the most implausible aspect.Why would anyone live on the top floors? I can see using the roof as gardening space and stationing a lookout up there, but walking up 12 to 18 flights of stairs every time you go in, especially while hauling in whatever materials you've collected that day, just seems extremely burdensome. Why would people walk up an extra 10~15 floors for negligible benefit compared to living on the 3rd floor? Have you considered just how onerous that is? – pluckedkiwi Mar 6 '18 at 20:04

In order to get water up to the top of a building, you can either carry it manually, or you can pump it. Pumps don't have to run on electricity.

Wind-powered pumps use a windmill to power the pump, and have been used since at least the 1500s (and likely much earlier) for irrigation and other purposes.

Other options like steam power, diesel, or water wheels could also work.

Another option would be to use a hydraulic ram pump, which uses the inertia of the water itself to pump part of the water up.

• A plus: wind speeds tend to be higher at the tops of tall buildings. – Skyler Mar 5 '18 at 20:53
• Note that many wind powered pumps have their pumps at the level where water is used. The highest you can pump water when the pump is above the source is about 10 meters. So this will still work, but the actual pump needs to be at the ground level, not at the top of the building where the wind will likely be collected. – Samuel Mar 5 '18 at 21:30
• @Samuel does that apply to all pump types? The Archimedes's screw doesn't look like it would care where the power source is (although the need to maintain the 45° angle and so change direction periodically might be a bit of a nightmare) – Richard Tingle Mar 5 '18 at 21:35
• @Samuel I believe that the classic windmill pump was actually at the bottom of the well that the tower stands over, with the control rod coming all the way up out of the ground and continuing to a swivel joint just before reaching a crank at the top. That would also be self-priming because the check valves are always wet, which is really nice for unattended operation in intermittent breezes. column_height x flow_rate is still limited by the amount of power that you can get from a given size disk, but at least you're not trying to draw a vacuum all the way up the OP's skyscraper. – AaronD Mar 5 '18 at 22:32
• @RichardTIngle It applies to all types where the pump is at the top (because they rely on air pressure to push the water up); an Archimedes screw is all along the pipe, not just at the top so it doesn't apply. – user253751 Mar 6 '18 at 4:51

The oldest pump in historical records is the force pump. The book that first describes it was written between 15 and 30 B.C/B.C.E.

This is the Archimedes's screw, which is one of my favorite ancient machines. It was used for irrigation. These could be arranged within a building's staircases.

And then there is always the classical bucketwheel.

All of the machines above were operated by human power, but with some clever tech'ing around post-apocalypse survivors could make animal, wind, steam or coal based versions as well.

To clarify... the force pump is nothing but an alternate name for the hand piston pump seen all over "pre-electricity" England and America. en.wikipedia.org/wiki/Piston_pump

And if you've scrounged a bicycle, you can connect the rear sprocket to the pump. The Google search "bicycle powered water pump" is rife with examples.

-RonJohn

And

Bucketwheels have an advantage in that if you place them in a suitable location you can power your bucketwheel with a waterwheel. Couple that with a nice storage system and you've got pressurised water at no extra labour cost.

-Joe Bloggs

• To clarify... the force pump is nothing but an alternate name for the hand piston pump seen all over "pre-electricity" England and America. en.wikipedia.org/wiki/Piston_pump – RonJohn Mar 5 '18 at 19:38
• And if you've scrounged a bicycle, you can connect the rear sprocket to the pump. The Google search "bicycle powered water pump" is rife with examples. – RonJohn Mar 5 '18 at 19:40
• Bucketwheels have an advantage in that if you place them in a suitable location you can power your bucketwheel with a waterwheel. Couple that with a nice storage system and you've got pressurised water at no extra labour cost. – Joe Bloggs Mar 5 '18 at 19:43
• Idea: If those machines could be both human powered and animal powered I see no reason why they couldn't be zombie powered :) . Yeah, yeah, it's risky, but in post-apocalyptic settings you usually don't see a lot of security auditors. Which... makes sense. Looking at the world, they must be swamped and seriously undermanned. – xDaizu Mar 6 '18 at 7:59

Steam it up with a solar concentrator.

This London skyscraper can melt cars and set buildings on fire

The building — designed by internationally renowned architect Rafael Viñoly — is a dramatic edifice with curved exterior walls. Built at 20 Fenchurch Street in London's financial center, the 38-story skyscraper is known locally as "the Walkie-Talkie" for its unusual shape.

But that curvilinear shape is exactly what's causing the problem: The south-facing exterior wall is covered in reflective glass, and because it's concave, it focuses the sun's rays onto a small area, not unlike the way a magnifying glass directs sunbeams onto a superhot pinpoint of light.

So too the buildings of your people. They have affixed mirrors such that in the middle of the day, the suns rays are reflected from the buildings onto a boiler below. This boiler at ground level has been filled by the spring, and when heated to boiling, the steam moves up the building's internal standpipe to the rooftop, where it is condensed in a radiator.

The cool thing about this is that it would be disclosed early in the story as a utilitarian way for these survivors to use what they have to move water. But what they actually have is an Archimedes Heat Ray which I am sure they will find use for as the story unfolds.

• I'm pretty sure i got as far as "ready-made zombie killing field via London skyscraper" before getting completely distracted. – Roddy of the Frozen Peas Mar 6 '18 at 0:46
• I too was going to mention using evaporation, although not require a solar concentrator. The people could burn pretty much anything, if the column was well enough insulated the temperature could remain more less constant (a ceramic pipe with asbestos insulation would certainly be your friend), then near the top, the water could be condensed with metal tubing. The nice thing is it also provides a means of gathering materials at the bottom and heating the people who live at the top at the same time. – Quaternion Mar 6 '18 at 18:24
• This is not nearly sufficient for agricultural purposes in terms of output – wedstrom Mar 8 '18 at 0:31

All these answers are boring and practical. I see no hard-science tag... Where's the fun in reusing well-established methods that are basically guaranteed to work quite well?

Find the materials (somewhere, somehow) to make a giant tarp and cast it across the 6 buildings. Put a post in the middle that goes to the ground so that the middle of the tarp is raised. This creates a much larger rain-catcher than just the one building. If the buildings are really oriented as in your picture (I realise they may not be), You should get three of the 6 buildings receiving rainwater.

Also, getchou some bridges between your buildings. That would be cool.

• "Where's the fun in reusing well-established methods that are basically guaranteed to work quite well?" Quickly dispensing with the statement "a windmill pumped water to the tops of the buildings" (which everyone intuitively understands) gives you more time for the action, while not leaving room for stray user thoughts like "if the buildings are 50 yards apart, 1/2 inch of rain will weigh 23,000 kg; tarps won't hold that much water." (If my conversion is wrong, please correct.) That breaks suspension of disbelief. – RonJohn Mar 5 '18 at 22:42
• Building such a catcher would be no mean feat. Also, anchoring it against the wind isn't going to be easy at all. – LSerni Mar 5 '18 at 23:09
• It might break suspension of disbelief for you. That doesn't mean it does for everyone, or even most people. Basically every popular sci-fi movie breaks physics worse than this. Plus, you're forgetting that it doesn't have to hold the water all at once, and that the normal force on the tarp is not equivalent to the weight of the water. You can raise the pole until the normal force is small enough to hold the water. – Nacht Mar 5 '18 at 23:21
• Depending on the area of the buildings and the rain fall of the region the tarps might not be required. – user25818 Mar 6 '18 at 0:10
• One of the beautiful rules of breaking immersion is that if you try to follow the rules and miss people get upset, if you throw the rules out of the window before you start nobody minds. Hence warp travel is ok. – Separatrix Mar 6 '18 at 8:14

A standard manually operated high-lift water pump can pump water 45 metres or more (your target building is 42-63 metres).

The height to which a hand pump will lift is governed by the ability of the pump and the operator to lift the weight in the delivery pipe. Thus the same pump and operator will be able to achieve a greater lift with a smaller diameter pipe than they could with a larger diameter pipe.

Assuming a water source at ground level and a vertical pipe 45 metres by 7 cm diameter, that is 173.2 L (or kilograms) of water when the pipe is full. This is well within the ability of some adults to lift on their own, and definitely within the ability of two or more operating the pump handle.

A series of storage tanks and pumps constructed on lower floors could break up the pumping process into stages, making each stage easier.

• Ha, the Wiki article says "0 – 45 meters, or more", which covers all positive numbers. – Samuel Mar 5 '18 at 21:43
• The pump in your picture is a cistern pump that can draw water up no more than 10m. You'd normally find that pump indoors, on the kitchen countertop, and it would draw water up from a cistern in the basement. The piston and cylinder of a deep well pump are located at the bottom of the well, and connected to the handle at ground level by a long iron rod. The handle typically has a heavy weight at the end to counterbalance the weight of the iron rod and the weight of the water. – Solomon Slow Mar 6 '18 at 0:35
• The picture is just to get across the main concepts. This Afridev hand pump operates the same way, rated to a depth of 45 m, and looks the same. – rek Mar 6 '18 at 1:29
• The Afridev pump appears to have a second pump at the bottom of the well to push water up as James mentions. – Separatrix Mar 6 '18 at 8:12
• @Samuel It does more than that! It covers all non-negative orderable numbers! – wizzwizz4 Mar 6 '18 at 16:59

The people living on the top floors can power the pump as they travel down, by lift/rope. Let gravity work for you.

Obviously this doesn't bring up enough water, but can be used along with better solutions. We had such a setup in one summer camp and the kids would happily run up and go down over and over again :-)

• It brings up their weight in water. How much do they need? – Harper - Reinstate Monica Mar 7 '18 at 23:55
• Nope, @Harper , they can only bring their body weight up to the middle of the building (if they drop from the very top)... Anywho, a quarter of their body weight to nearly the top may be enough for drinking, basic sanitation. They can shower in the nearby lake every couple of months. – Nahshon paz Mar 8 '18 at 15:30
• If they're using the water as a counterweight to control their descent, and their basket is on the top floor and the water counterweight of equal weight is on the bottom floor -- they'll really want the counterweight the whole way down. When they finish they will be on the bottom floor and the water will be on the top floor. They will need to unload the water to take the next descender. Assuming this rig has a brake, this is all easy. – Harper - Reinstate Monica Mar 8 '18 at 16:01
• @Nahshonpaz err... if you're exactly the same weight as the counterweight, you're going nowhere (imagine if the counterweight was heavier than you). You need to be slightly heavier. the heavier you are, the faster you'll go down, and you'll go all the way down. – gbjbaanb Mar 8 '18 at 19:09
• Right @gbjbaanb , I was thinking in terms of pressure (pipes pushing water up per the weight pushing down) – Nahshon paz Mar 13 '18 at 9:35

One way of pumping water without needing any external energy source, other than the water itself, is a hydraulic ram.

It wastes water since it only pumps a fraction of the water that is made available to it but it can keep pumping without the need for any wind, solar energy, animal muscle, human sweat, etc.

• If you have a running spring, then this is the most reliable option – James K Mar 6 '18 at 23:46

I hesitate to mention this, being so simple, but since tall buildings already often have a large water tank on the roof (an estimated 15,000 in NYC) and an electric pump at ground level to get water up to it, could your people not simply run that pump for the limited length of time it takes to top it off each day?

Running the pump would give you something productive to do with any solar electricity not otherwise needed during the day.

Also, in ANY scheme, according to this white paper, the top 6 floors would not have the current water pressure, since the tank isn't high enough above them to provide it by gravity, so although the water would flow, there would be less pressure than previously. This would, ironically, pose a problem for water-saving shower heads.

If the water tank is sized to provide for the needs of the the whole building full of people, it could last several days supplying the needs of a fraction that number, especially since they'd initiate water-saving measures while under siege.

Note that this whole answer doesn't really apply in Europe, where rooftop water tanks are rarely used.

• It's a matter of priorities. Do you use your valuable generator fuel to pump water (which could be pumped by a windmill) or to run refrigerators which need a lot more voltage and amps than water pumps? – RonJohn Mar 5 '18 at 22:55
• Electrical guy here, refrigeration doesn't take that much. You might even be able to do refrigeration with an Aermotor type windmill, since the crux of refrigeration is pumping (freon) and "cold" stores reasonably well. – Harper - Reinstate Monica Mar 6 '18 at 18:02
• @RonJohn That makes no sense; IF the pump doesn't take much then you may as well run the pump. (But if the pump takes a lot, then it makes sense) – user253751 Mar 7 '18 at 0:49

Let me draw you a picture. Two pictures. And an equal sign.

Aermotor has been making these things since 1888, and they're hardly the first manufacturer. I don't know how many folks have lived in rural areas, but 180' is not that deep for a well. You can also see the windmill atop the building catching nice wind, to say nothing of wind gradient effects which already slow wind near the ground.

• Worth 2000 words ...plus an equal sign. – Penguino Aug 6 '19 at 21:47

Where you use water, there you get waste water. You need to supply fresh water up, and you need to get waste water down. The amount of both will be roughly the same.

Now combine the two: Use a long rope, hang it over a pulley at the top of the building, and attach two large water containers to it, a blue one for fresh water, and a brown one for waste water. Use is as follows:

1. You fill the blue tank at the bottom of the building with fresh water.

2. You fill the brown tank at the top with waste water.

3. Both tanks are almost perfectly balanced, a single man can now move a ton of waste water down while moving a ton of fresh water up.

4. Empty the blue tank at the top into a fresh water basin.

5. Empty the brown tank at the bottom into a sewer.

6. Move the two tanks back into their starting position, rinse and repeat.

The order of the steps is somewhat important, otherwise this is as simple a solution as it gets. Should be quite easy to implement in your post apocalyptic world, it allows you to move large amounts of water quickly with very little effort, and it does not require any energy use or complicated setup.

Bonus points if the point where you load the fresh water is significantly higher (strong well has some pressure that allows the water to rise a floor or two above the ground) than the point where you dump the waste water (think cracked sewer next to the building). This would allow your protagonists to distribute flowing water throughout a few floors at the top of the building. Any floor between the waste water tank and the fresh water basin can have fresh water delivered and waste water removed by gravity.

More bonus points, if you also collect some rain water at the top of the building. With that you can ensure that you have always more waste water that goes down than fresh water that goes up. Consequently, you won't have to move the water yourself, you just need to apply some brake on the rope/pulley to avoid the tanks becoming too fast. Gravity will do the work for you.

Finally, as Peter Cordes points out in a comment, there is also the possibility to use two pulleys, one on each side of the building. This has several advantages: First, it would provide for a better separation of fresh and waste water, second, it would provide the operators with a convenient horizontal rope piece that can be grabbed to move the tanks, and third, it would make anchoring of the pulleys much easier. The simplest solution would be to just place a long, strong beam across the roof of the building, and fix the two pulleys at either end. Since the forces on both sides are almost perfectly equal, you would not even need to anchor the beam at all. A little more involved solution could look similar to this:

              v rope carrying tanks v
o---------------------------------o
|\---------------+---------------/|
| \ ^ support ^ / \  ^ rope ^   / |
|  \           /   \           /  |
|   \         /     \         /   |
|    \_______/_______\_______/    |
|     ######## roof  ########     |
|     #######################     |
v     #######################     v
fresh   #######################   waste
water   #######################   water
tank    #######################   tank


If the four diagonal beams are held in a 45° position by the support rope and each other, there will be no bending forces on the structure whatsoever, and the anchoring will be next to trivial.

• Interesting, but do you really want to be handling sewage that much? I'd expect some minor spillage in the process of collecting the sewage, and without a good water supply it's not convenient to just shower off, so it's more disease risk for your population even just to keep sewage sitting around in the open until its time to lower it down and use it's gravitational potential energy. – Peter Cordes Mar 7 '18 at 23:45
• Still, with two pulleys, the tank going down could be on the other side of the building from the tank going up, so cross-contamination at the bottom could be limited. – Peter Cordes Mar 7 '18 at 23:46
• @PeterCordes That is actually another good idea, as it would not only serve to thoroughly separate the tanks, but also help in anchoring the pulleys: A long, strong beam would be enough as the force is the same on both sides of the building, precluding any danger of tipping over; when the pulley(s) are just on one side of the building, you would need some thorough anchoring and/or counterweight to counter the tipping force. I think, I'll add that to my answer, thanks :-) – cmaster - reinstate monica Mar 8 '18 at 21:12
• @PeterCordes I've added your idea to the answer now. Hope you like it the way I wrote it. – cmaster - reinstate monica Mar 8 '18 at 21:44
• Yup, looks good, and good point about the forces on a beam sticking out past the side of the building. Thanks for writing it up with ASCII art :) – Peter Cordes Mar 8 '18 at 22:07

## An Archimedes' screw, or a series of them at different floors.

The device consists of a helical surface surrounding a cylindrical shaft, which in turn is placed inside a hollow tube. Rotating the helical surface (the screw part) or rotating the entire tube (if the helical surface is attached to the tube) will transport water up.

Said device can transport water so long as there is sufficient power to turn the screw against the weight of the water and the device itself, with longer screws obviously weighing more, as well as carrying more water.

Ancient versions were powered by hand, or even by foot. It would be fairly simple to rig them to a wind powered turbine. It has also been used as conveyors for particulate matter, such as grains.

• In a post-apocalyptic world the simplest way to construct an Archimedes' screw is with a helix of garden hose. – A. I. Breveleri Mar 10 '18 at 3:11

Are there any hills nearby that are taller than the buildings?

If so, build a reservoir at a higher altitude than the top of the buildings, connected via pipes to water tanks on the tops of the buildings, such that water from the reservoir flows downhill under gravity, and then up the buildings into the tanks.

Obviously, the reservoir will need some additional altitude to overcome losses in the process (e.g. leaks, restrictions in flow, etc).

• Unless that reservoir has a surface large enough that rainfall is enough to fill it up, you've just moved the problem from one place to another... – jcaron Mar 9 '18 at 1:37

For something that should be within the bounds of simply modern engineering I would suggest a water tower and wind pump. A water tower stores water above ground at a sufficient height to produce pressure (by way of gravity); this water pressure is typically fed into water pipes to force it up through sinks and other systems in our buildings.

This of course still requires some way to get water into your water tower: wind pumps are simple wind turned pumps that pull water from some source (river, spring, or lake) and pump it else where (historically a lot of irrigation and draining). Their imagery is often associated with old farms.

This is a little crude, in more ways than one.  Perhaps somebody can suggest improvements to (cough cough) clean it up.

First of all, they’ll want to have a reservoir (or cistern) at (or, more likely, below) ground level.  This would allow them to capture and hold spring water temporarily, in case the spring and/or the pumping mechanism have varying flow rates.  (I’ll get back to that.)  If they’re collecting rainwater at ground level, they’re probably already doing this.

As in initial capability, immediately after the apocalypse (or maybe even before), this could be as simple as a pond around the spring.  Given time to establish some infrastructure, there should probably be such a cistern in each building; this provides some security against bandits/raiders.  Rig something so that the water from the spring runs through pipes or other channels into the holding tanks in the basements of the buildings.  (Try to make it hard for attackers to slip poison into the reservoirs.)

One added security measure is “security through obscurity” — after you have built a plumbing system that pipes the spring water into the buildings, bury it.  This may make it somewhat harder for adversaries to steal your water or tamper with the system.  Ideally, it will make the spring invisible.

The question of getting the water to the upper floors remains.  Renan suggested a “bucketwheel”:

but handwaved the power source.  (For the record, I thought of this before I read the answers.)  If there’s power to spare, there are many options.  But the question said that all the solar power is accounted for, and that fuel (for the generators) is scarce, and I assume that the building complex isn’t within walking distance of a forest, a coal mine, or an oil well.  If the spring provides enough power to drive the bucketwheel (or bucket conveyor belt) and lift water 18 stories, that’s great, but that strikes me as unlikely.

One idea that hasn’t been mentioned is to have a dual-track bucket conveyor belt.  One track would bring water up; the other would take waste material down, and thus provide the power to drive the belt and lift the water.  I am thinking specifically of toilet-type waste.  There might be others, but I imagine that these survivors would recycle as much as possible.

The rate of disposal of waste varies with the time of day.  This is why it’s important to collect the spring water all the time, so the water that emerges from the spring overnight, and at other periods of low waste-disposal activity, doesn’t just go into the ground.

Of course, if they’re using washing water, urine and feces in their gardens, this won’t work.

• Wow.  I just noticed that slomobile just posted an answer that has a lot of overlap with mine.  Again, for the record, I wrote my answer long before he posted his. – Peregrine Rook Mar 6 '18 at 23:11

A method might be a modified, large solar still.

Basically you have the sun heat up a pool of water, where it rises to a place where it can condense back into water.

It's often used as a way to purify water, but in your case, you can use it to raise the water up:

You could use a parabolic reflector to concentrate sunlight, to heat water in the base at ground level:

With enough energy, you can create a steam pipe that will raise the water up to the top of your buildings. Then, have a place where it cools, and you have water.

Possible without pumps? Not really. A "pump" is just a device that adds energy to water, letting it flow against gravity; however, electricity is just a convenient way of moving energy around quickly, and humanity has been using pumps long before the invention of electricity. Here's a page about various methods the romans used for lifting water for their aqueduct system. Additionally, most modern water pumps (that might be left over salvage in a post-apocalyptic scenario) can be separated from their electrical motors and driven with a rotating shaft that gets it's power from anywhere.

The question you'll have to address is not so much "Can water be lifted without electricity", but "Where does the energy come from to lift all this water?" Since you say that there's not enough leftover energy from generators and solar panels to do this work, we can look to other methods of harnessing energy that might be available.

Since your society is already living high-up, and since they might not have the food/space to support beasts of burden to turn cranks all day, I think an obvious solution is wind power. A set of windmills on the roofs, and maybe even attached to the sides, could provide a ton of usable energy. This could be used to drive mechanical processes all through the building, with the most advanced technology being gear boxes and crankshafts. They could even be used to turn a generator; probably not fast enough to use the energy directly, but it could be stored in salvaged batteries for later use.

As additional food for thought, pumping water up to high places is a form of energy storage itself (still used today). Maybe your society uses wind power to slowly pump water to the top of the building, and then when the wind is dead, the water can flow back down through some water turbines to generate electricity that way. There're lots of ways to access and store energy in the world around us!

I love how no one said: The use a very tall pipe.

Let me introduce you to artesian well. You take water rich enviroment, put one end of pipe in it and water appear on other end.

And for those who say: but the pressure won't push water up to the top. I say: you are terrible picky for someone living in post-apocalyptic environment. If poor Mugabe can take 20 kilometres walk for water right now you can take a few steps to the terrace with water for plants.

Also I'm all in for the fact that this is terrible design for defence. Much better are to reuse some medieval castles that were build for siege, with water resource that couldn't be poisoned.

i would point out some tecnical design: vacuum pump can go up to 10.3meters, then you would need to fill a pond and from here start again. A positive pressure pump can do much more, 100 psi (7 bar) is enough to get you over 70 meters, at which case you just install another pump for your next 70 meters.

Please note if you attach your implant directly to the tube the pressure can be pretty high; the safe solution is the pump filling a non-ermetic container close to your applicance, where the pressure will drop to normal atosfere, and normal gravity is used.

Those tall building prbably have lift: even witout power, those thing can be relatively easily moved by hand, as they have counterweight, so that, even if manually operated, would be your main way to carry water and other stuff in your top floors.

• Since OP mentioned “bandits,” I wouldn’t rely on lifts. Shorter ones are often hydraulic, and those with cables and counterweights can be disabled by cutting the counterweight off the cable. Of course, ANY method of getting water from the ground can be broken by bandits on the ground. And if you have the ability to defend what you’ve got on the ground, then why would you need to live up high? – WGroleau Mar 6 '18 at 12:07
• High ground is needed to spot the enemy, longer range of attack, defend from wild animals and quick raid. Please note those rendered building are quite tall, so it is probably not idraulic. if you can't defend the fundation of the building you are dead, enemy can just lit a fire until the the building loose integrity and fall by itself. This demolition method was used from Romans up until 1980-1990, you can find example on youtube. You could secure the lift and counterweight by positioning them on middle floor to protect them. Also it is relatively easy to fix – Lesto Mar 6 '18 at 17:11
• @WGroleau Human bodies are ludicrously fragile. It's entirely possible to build a pump enclosure next to your building, over the spring, during a quiet time when all the bandits happen to be elsewhere, and make its outer casing sturdy enough to be very easily defended from things that would be nearly impossible to defend an exposed human from. – Matthew Najmon Mar 6 '18 at 22:46
• @Lesto: positioning both lift and weight in the middle would work for protecting them, but if someone did Sever the cable, to fix it, you would have to get the cab to the top without electricity and without counterweight and hold it there while working would be on the bottom, which require defense. Of course, if the have enough resources to make an Archimedes screw, … – WGroleau Mar 7 '18 at 0:08
• @WGroleau when you position them in the middle you can also secure them (lift has already some multiple block mecanish and even emergency brake), severing the cable is quite a damage but not that complicated. The archimedes screw on the other end are always exposed in the lower level, and require a large amount of power to operate. – Lesto Mar 8 '18 at 21:43

For the plants aeroponics could be used, using light pipes and shade-tolerant plants near windows initially, where the water supply would be via capillary action in an artificial supply of roots. Ropes would be sent into the ground, to gradually branch out into ever finer capillaries leading to every individual plant. Capillary action will raise to tree top height.

• I don't understand the down vote. Using plants, vines in particular, if chained could certainly lift water. Being in the future the vines could be engineered for such and might also be edible. Certainly they wouldn't lift a lot but plants can lift water astounding heights and all they ask for is sun. – Quaternion Mar 6 '18 at 18:39
• @Quaternion correct. Further, one of the inhabitant's real problems would be in prevention of growth. As vines and ivies took hold, light would diminish, facades would begin to weaken, insect and rodent infestations would occur. – Sentinel Mar 7 '18 at 5:15

If "there is a strong spring and a well in between the buildings", it would already be integrated into the municipal water supply. Ignoring such a resource is as silly now as it would be post apocalypse.

Close any valves exiting the neighborhood.

Work with resources already in place. Running any kind of new infrastructure 12-18 floors without power is more work than its worth. It would be very convenient(and plausible) if the tallest building were still under construction allowing crane access and heavy equipment on site.

Windmills on the ground are enough to simulate a low pressure municipal supply to each building which will serve the lower 2-3 floors. But above that, the buildings will rely on either pressure booster pumps or transfer pumps to a roof tank. The electric motors in these pumps can be removed and the pump portion powered by some alternative source. Unfortunately, getting the power source to the pump location can be a very large problem.

With the tallest building still under construction, a wind turbine could be raised by crane and placed on an unenclosed floor inside the building. That windmill power would lift water to a simple tank built on the roof or upper floor. The tank could be tied to the building's standpipe. Then all the standpipes could be linked with firehose at street level. Because water seeks its level, it will rise to the top of each standpipe in every building. The existing plumbing on living floors only would be tied into the standpipe. This would prevent an inadvertently opened faucet in an unoccupied room from draining the system.

If there are ever problems, a pumper firetruck could always be used to quickly inject lots of volume into the system.

http://www.who.int/water_sanitation_health/hygiene/plumbing14.pdf

An different solution I thought of is to use the elevator to lift containers of water or whatever else you need. The elevator motor wont work, but the counterweight is still attached to the cable. If you could attach additional weight(buckets or tanks) to the counterweight at a high floor while the elevator car is at ground level, that would allow the elevator to rise without power. Unload the weight at the bottom and the elevator car comes back down.

You don't want to carry weight up the stairs just to drop it down the elevator, so what do humans living on upper floors produce which weighs a lot, and which they want far away from where they live? ... sewage. Yes, I just proposed a human waste powered elevator on a question that asked nothing of the kind. I should get out more.

• It’s not a bad idea; I thought of it too. Congratulations on posting it first.    :-)    ⁠ – Peregrine Rook Mar 6 '18 at 23:13

How about passive rain / fog collectors at the top of the buildings? Unless your post-apocalyptic city is Las Vegas... Fog collectors are large permeable fabric panels that intercept the flow of fog-filled wind on hilltops and ridgelines, and collect hundreds to thousands of liters of water per night. Fog collectors have been erected in Namibia and Peru to provide water for personal needs, cooking, and agriculture.

• Welcome to Worldbuilding! Sometimes, links can be taken down, so we like answers to quote or summarise relevant parts of the link. As such, would you be able to edit your answer to give an explanation of what rain and fog collectors are? Thanks! – Mithrandir24601 Mar 5 '18 at 22:05

Steam Engine

Before there was electricity there was steam. Steam engines are fairly basic machines. Further our current society has plenty of refined metal that could be used as the basis for redeveloping this technology. Assumably you could just burn wood in place of coal. This option would likely not provide as much power but it is viable. Finally, the steam engine could be mounted two or three floors up for defence -- you would have to rely on animal / human power to position the fuel.

Note that there are forests near cities. The green areas in the map below area parks often dominated by forests (the map is of the Cleveland Ohio metropolitan area):

• Where do they get the wood and coal (lots of wood and/or coal) in a post-apocalyptic city? – RonJohn Mar 5 '18 at 21:01
• It's a city, I suspect there's plenty of wooden furniture to be broken up! – Ruadhan Mar 6 '18 at 11:13
• Ruptured steam vessels whilst experimenting with how to shape copper might result in unwanted casulties. With a settlement where knowledge is power i'd rather not experiment with technology that might go boom especially if you don't know what you're doing... – Tschallacka Mar 8 '18 at 12:10

Since we're including impractical answers, behold my favorite weird way to raise water: the fluidyne pump. It's a heat engine closely related to the more familiar Stirling engine. Fluidynes can be powered by sunlight, but you'll need a lot of them in series to reach the top of a tall building.

A windmill may not produce enough "power" to work a pump depending on location, how much wind is blocked or scattered by building, and it might get scavenged for its materials by raiders so wind may not be the most reliable way to get stuff working(depending on the setting)

I'm assuming the survivors will need to wander off into farming as well to be able to eat, and as humans are lazy, they will use mules/horses/cows to till the soil(even if the soil is inside a building with a glass roof or mirrors set up)

Now if you'd occasionally hook those cows and mules up to a water pump the settlers built out of wood or metal if they have proper metal working tools available for the water crisis sets in.

http://users.tpg.com.au/wagnerbe/hpv/html/horse_drawn_pump.html

and have those pumps pump the water up to a big water tank, which is relatively easy to build out of wood, you only need your work animals to work once in every x days until the water runs out. That way you can get the animals out of harms way and "hide" the pump for marouders. You could even dig it in the ground and then cover it up.

These animals could also be used to automate washing for the people living there https://youtu.be/6tMoE8siNo8?t=5m54s

and of course power grinding stone for grinding grains and other materials.

They can also used to power machinery with leather belts.

https://en.wikipedia.org/wiki/Line_shaft

or generate electricity with it. Small amounts, but perhaps enough to help with building up an electrical grid up with windmills/watermills etc...

Basically, by first utilizing animals, they could short circuit the industrial revolution within a few years if they manage their resources correctly and focus on getting power from windmills/water mills as soon as possible on large scale.

When there's power, water, electric light, they can grow crops galore, which they can trade with other settlements and get an economy back up and running. They can smelt metals with electricity and get iron working back up and running.

Perhaps this is a novel solution, but you could use a space pump.

Simply build a tube--like a chimney--to the top of your building. At the top of your building, the chimney opens out into a dome, perhaps with a glass surface.

On this top level, you have a bunch of soil and plants, because that is nice and aesthetically pleasing.

At the bottom of the tube, you have a nuclear reactor and a water reservoir that allows water to fall towards the reactor. The nuclear reactor vaporizes the water passing over it, which is used to power a turbine (much like the turbine of a jet engine) at the bottom of your tube (providing energy).

This steam then expands and flows up your tube to warm the jungle at the top of your tower, and condense on the dome.

As the water condenses and filters through your jungle/farm, it flows back down to the nuclear reactor.

Bear in mind, this nuclear reactor could also power a plasma that is almost energy neutral (as in a tokamak--so it is basically free) ejecting near-massless particles at significant fractions of the speed of light out the bottom of your building, providing nearly 1g of thrust for your inhabitants.

Further, once you get up to speed, the blue shift of the stars in front of your space pump will produce enough light to stimulate photosynthesis in your jungle (at the top of your building)...and voila, you have an interstellar space pump that not only transports water, but also grows food for you to eat and moves you around.

You could probably build an economy around water carriers. They could walk up the stairs all day with the water, for a fee.

Some answers are wrong, it is not possible to pump water from above, if the height is higher somewhat like 10 meters (10 meters of water is 1 atm of pressure), over 10 meters you can drain water only if there is some pressure underground.

However you could have some series of pumps each one draining a well that is 5 meters below.

1. Pump 1 get water from ground level and push it to a 5 meters tank,
2. Pump 2 get water from the 5 meters tank and pull it to the the second tank at 10 meters etc.
3. And so on.

If the height is particular high, another feasible way is a mobile tank, it is filled at ground level with few hundred liters, then it is pulled to the roof (by hand in example).

What is the nature of the apocalypse your world was subjected to? Assuming this world evolved from our timeline, it will have experienced global warming. If that's the case: let the water come to you. At the tops of at least some of these abandoned buildings are former swimming pools, which are kept filled with freshwater by regular heavy rains and serve as large reservoirs for the inahbitants. The rains also irrigate the building-top gardens, mitigating the need for pumping technology.

I might be thinking too simply on this but why not use a dumbwaiter run by the people in the towers. being enclosed the cable and pulley system should be protected against bandits and as long as someone can pull a rope or cable you have a way up and down.

Brief history. Over 80 years ago, a Moldavian boyar brought from a western country (Germany, France) dpua pumps that he used to remove water from the fountain to the mansion and the water lifting field.

Description of the pump: it was made up of a cylindrical body with semispherical lids (everything made of cast iron), one of the parts had a pipe (the inlet) that was above the level of the fountain and had the end provided with a r1 tap and above palnie (p). from the other end of the body there was another pipe (slightly) bent at the end and fitted with a r2 tap. More about drilling water well here.

installation: the pump body was immersed in the well until the bottom, and the two pipes - the inlet and the discharge - stayed above the guides (the upper edge) of the well.

operating mode: 1. Open the drain cock r2 as well as the intake faucet r1. 2. pour the bucket water through the pallets filling the entire system until the water flows through the r2 tap. 3. Close the taps r1 and r2, then open the robot r2 and the water starts flowing smoothly without having a large flow. as a rule the water was flowing in the well of the fountain because the springs were strong.

If the r1 faucet opened, the system would be defused and the water would not flow through the r2. The pump that was installed in the field raises the water to the pools for the preparation of the spraying solutions.

What a "diabolic" mind had that engineer from recent times gone! it is worth mentioning that two unofficial commissions from the polytechnics in Iasi and Bucharest were asked to address the issue, and they were brought by a clever director from an i.a.s. nearby. unfortunately, the pope had disappeared, because some villagers could no longer feed the cattle, feeling the taste of oxides in the water.

The description belongs to people who are trustworthy.

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