# Hypothetical question about pumping water **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 31, 2026, 8:28pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726 "2026-08-31T20:28:46Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [August 31, 2026, 8:28pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/1 "2026-08-31T20:28:46Z")
You have built a house on a hill with a really good view. Now for the water problem. The water available to your house is a large lake, 50 feet below the hill. You do not own any of the hillside, but there is an easement that allows you to run a pipe down to the lake. That, and only that.        This is an obvious problem, because physics tells you that you cannot pump water more than about 30 feet up, and you are forbidden from putting any equipment on the hillside to make up the difference.        My question is this: your suction pump is still pulling stuff out of the pipe – water vapor and air; would it be possible/feasible to feed the pump output into a large condenser in the attic such that it would allow you to actually get water to your house? (For the sake of argument, the easement restrictions and the considerable traffic of various kinds on the hillside make it impractical to put a small screw turbine down in the pipe to assist in raising the water.) ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 31, 2026, 8:35pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/2 "2026-08-31T20:35:42Z")
So this is not actually a question about getting water to the house (something to make it possible would presumably be included in the easement language) this is about the pump? (Because collecting and storing rain water also comes to mind, as does paying to have water trucked in. I have a friend in the Australian outback who uses those two methods.) ---
**Author:** ![ricepad](https://avatars.discourse-cdn.com/v4/letter/r/b38774/32.png) [@ricepad](https://boards.straightdope.com/u/ricepad)\ **Post date:** [August 31, 2026, 8:54pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/3 "2026-08-31T20:54:39Z")
Possible but not feasible. It’d cost a small fortune to run a pump to capture enough vapor to condense water for household use. Better to put the pump in the lake. If the easement won’t allow that, then drill vertically until you hit the water table, put the pump at the bottom of the shaft, and pump water up. With a lake in close proximity, you shouldn’t have any problem drilling to hit water. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 31, 2026, 8:56pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/4 "2026-08-31T20:56:28Z")
The general construction you are talking about is called a “cold trap”. This is something one puts in front of a pump (not on the output). This is routine in vacuum laboratory practice, but would be impractical for any high-throughput, food-grade application like you describe. Can you go straight down with a well? (ah, ninja’d on the well idea) ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [August 31, 2026, 9:02pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/5 "2026-08-31T21:02:40Z")
No one is obligated to help you have water at your home. If municipal services are not available it’s on you. Water is not a right, it’s a privilege. A buyer needs to know these things in advance. And far as the pump goes you’ll need the biggest one you can get. And keep spare parts because you’re always gonna be working on it. I guess you might get the owners of the hillside to allow you a pump station halfway up. I wouldn’t bank on it. Best bet is to not have the issue, if you do I’m sorry for your plight. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 31, 2026, 9:09pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/6 "2026-08-31T21:09:09Z")
> [@Beckdawrek](#): > > And far as the pump goes you’ll need the biggest one you can get. As others (including the OP) have already mentioned, if the pump is only at the top, it won’t matter how big it is, it won’t work. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [August 31, 2026, 9:11pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/7 "2026-08-31T21:11:44Z")
Ok. I think hypothetically there’s gotta be a huge industrial one. I realize it’s not viable for home use. But in theory. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 31, 2026, 9:12pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/8 "2026-08-31T21:12:15Z")
> [@Beckdawrek](#): > > Water is not a right, it’s a privilege. > [@eschereal](#): > > there is an easement that allows you to run a pipe down to the lake. Doesn’t the easement establish a right to the water? And actually the [United Nations recognized](https://www.un.org/en/global-issues/water) that people have a right to water (and sanitation). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 31, 2026, 9:17pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/9 "2026-08-31T21:17:31Z")
The OP is about the ohysics of pumps and suction. The house, hill, lake, easements, etc., are all just distracting setup that could / should have been left out. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 31, 2026, 9:31pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/10 "2026-08-31T21:31:50Z")
How do you know that? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 31, 2026, 9:33pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/11 "2026-08-31T21:33:58Z")
Seems obvious to me from the highly contrived setup. With various practical alternative solutions carefully blocked off. I concluded from that setup that this is almost certainly a thought experiment, not an IRL dilemma. The word “Hypothetical” in the title is another tell. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 31, 2026, 9:45pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/12 "2026-08-31T21:45:35Z")
> [@Beckdawrek](#): > > I think hypothetically there’s gotta be a huge industrial one. I realize it’s not viable for home use. But in theory. It still won’t work. The problem isn’t the size. The problem is the Earth’s atmosphere. You can only pump water from above to a maximum height where the pressure of the water equals the pressure of the air. A small, low-power pump can pump water up 32 feet. It might not get very much flow through, but it’ll work. An industrial-sized pump powered by its own nuclear power plant can’t pump water up 34 feet, not even a trickle. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [August 31, 2026, 10:00pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/13 "2026-08-31T22:00:30Z")
> [@Beckdawrek](#): > > I think hypothetically there’s gotta be a huge industrial one. I realize it’s not viable for home use. But in theory. At the risk of stating the bleeding obvious, when a pump is at the top of an airtight pipe that is vertical or slanted downwards, water or other liquid is pushed up into the resultant vacuum by atmospheric pressure. Since atmospheric pressure at sea level is around 15 psi, this limits the maximum column height that atmospheric pressure can push, which for water is approximately 30 feet. Beyond that, water will go no further no matter how powerful the pump. For a very heavy liquid like mercury, the maximum column height is around 30 inches, and varies with local atmospheric pressure, which is how mercury barometers indicate changes in barometric pressure. ETA: Ninja’d by @Chronos > [@Beckdawrek](#): > > Water is not a right, it’s a privilege. While this has nothing whatsoever to do with the topic, it’s an absurd statement in the sense that clean potable water is a necessity of life. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 31, 2026, 10:06pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/14 "2026-08-31T22:06:11Z")
> [@wolfpup](#): > > > [@Beckdawrek](#): > > > > Water is not a right, it’s a privilege. > > While this has nothing whatsoever to do with the topic, it’s an absurd statement in the sense that clean potable water is a necessity of life I’d say morally water _ought_ to be a right. In the real world of economics and politics, water is _actually_ a privilege. Just like food and shelter, you’re able to get only what you’re able to pay for, not what you might need or want. And sometimes not even that much. Potable water shortages are a real thing here in the real world. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [August 31, 2026, 10:09pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/15 "2026-08-31T22:09:21Z")
> [@wolfpup](#): > > Since atmospheric pressure at sea level is around 15 psi, this limits the maximum column height that atmospheric pressure can push, which for water is approximately 30 feet. Beyond that, water will go no further no matter how powerful the pump. But if the pump continues to draw, it is drawing something out of the pipe. I presume the resultant vacuum causes the head of the column to boil/vaporize, so the pump _will_ pull _something_ out of the pipe, which should be a mixture of dissolved gases and water vapor, which one could theoretically condense back into liquid water. Perhaps adding a cooling loop at the top of the pipe could improve throughput a little. ---
**Author:** ![ricepad](https://avatars.discourse-cdn.com/v4/letter/r/b38774/32.png) [@ricepad](https://boards.straightdope.com/u/ricepad)\ **Post date:** [August 31, 2026, 10:10pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/16 "2026-08-31T22:10:16Z")
> [@Dewey\_Finn](#): > > Doesn’t the easement establish a right to the water? Nope. While it’s illegal in most jurisdictions in the US to sell property without a right of access, it’s perfectly legal to sell property without a known water supply. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [August 31, 2026, 10:17pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/17 "2026-08-31T22:17:08Z")
> [@LSLGuy](#): > > > [@wolfpup](#): > > > > While this has nothing whatsoever to do with the topic, it’s an absurd statement in the sense that clean potable water is a necessity of life > > I’d say morally water _ought_ to be a right. In the real world of economics and politics, water is _actually_ a privilege. > > Just like food and shelter, you’re able to get only what you’re able to pay for, not what you might need or want. Well, we’re really off on a tangent now! Politically, sure, things like diverting rivers or some other large-scale hydrological project that benefits one area at the expense of another is always going to involve economic and political issues and power imbalances. Much like the age-old battles over oil and mineral resources. But in civilized countries, at least, access to food, clothing, shelter, potable water, and medical care is available to all. If you’re very poor, it won’t be a great lifestyle, but you won’t perish or get sick from polluted water. > [@eschereal](#): > > But if the pump continues to draw, it is drawing something out of the pipe. I presume the resultant vacuum causes the head of the column to boil/vaporize, so the pump _will_ pull _something_ out of the pipe, which should be a mixture of dissolved gases and water vapor, which one could theoretically condense back into liquid water. No. Beyond 30 feet or so, the pump is just wasting energy. If you’re going to source your water this way, you’re likely much better off with big condenser coils getting it from the outside air. But even in conditions of high humidity, you won’t get much, and in dry conditions, you’ll get basically nothing. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 31, 2026, 10:18pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/18 "2026-08-31T22:18:48Z")
> [@wolfpup](#): > > No. Beyond 30 feet or so, the pump is just wasting energy. If you’re going to source your water this way, you’re likely much better off with big condenser coils getting it from the outside air. Yeah, you’ll have about the same amount of water vapor in the ambient air as you will at the top of your pump. The only difference is that the pump head will lack the air to go with that water vapor. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [August 31, 2026, 11:22pm UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/19 "2026-08-31T23:22:25Z")
> [@Chronos](#): > > An industrial-sized pump powered by its own nuclear power plant can’t pump water up 34 feet, not even a trickle. Redwood trees pull water up over 300 feet! But they use a clever trick (negative pressure). ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [September 1, 2026, 12:10am UTC](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726/20 "2026-09-01T00:10:40Z")
just put an Archimedes screw in the pipe. Or a chain bucket brigade. [Next page](https://boards.straightdope.com/t/hypothetical-question-about-pumping-water/1032726.md?page=2)