In my place, the city water system provides the water at pressure of between 2BAR - 4BAR. We live on the 3rd floor, with water boiler on the roof (5th floor) so the hot water are going up to the roof and coming back down, many times without a good pressure for a good shower..

The obvious idea is to add an electric water pump on the line to add pressure whenever someone is opening the tap. For some reasons, I want more sophisticated idea, that I think will be more reliable and helpful.

My idea was to add a pressure tank (like expansion vessel) with a bladder or diaphragm on the line (before the water boiler tank). To its "air side" (bladder or diaphragm) to connect air compressor with a dynamic proportional pressure regulator.

At some times on a day - the pressure regulator will let the air pressure in the bladder/diaphragm will let the air pressure drop down to 2BAR, so the water will come in from the city system (using the 'native' pressure, without a pump help). Other times, the air pressure will be raised to about 6BAR, pressing the water towards the home, and if the tank has - let's say - about 200 litre, it will have very long time until the next need to re-fill it.

I thought about 200-300 litre pressure tank (will be held at about 6BAR), with air compressor with 50-100 litre air tank (at about 8-10 BAR).

AFAIK - Such a bladder water tank of 200 litre will cost here about 250$, and air compressor will cost about 150$-200$. I'll also need the proportional pressure regulator and the plumbing, but generally that's it.

Am I right?

Any insights would be welcomed.

  • Is this work which you are permitted to perform? Sounds like an apartment. What would your landlord say? – MonkeyZeus Feb 17 at 19:44
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    Offer, I understand but your “pressure tank” having to be vented or valved off and around would be horribly inefficient, refilling without venting a costly method. Will you be able to afford a pressure tank large enough? Your ma. Pressure 8-10 bar these tanks require certification at my location fof much lower pressures 10 x 14.7 or 147 psi roughly. A small booster pump in a tank non pressure rated will be orders of magnitude cheaper to build and run. – Ed Beal Feb 17 at 21:47
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    Where are you on this planet? – ThreePhaseEel Feb 18 at 0:20
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    pumping water into a pressure tank is easier than pumping air. this is why off-the-shelf domestic supply pumps work that way. – Jasen Feb 18 at 0:34
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    Overcomplicating is not more sohpisticated, nor more reliable. – Ecnerwal Feb 18 at 13:51

Offer, I do not know of a regulator that will do what you want but it could be done with solenoid valves. You discuss a 200L pressure tank this is 52.8 gallons Even with low flow shower heads that’s not much shower time. my wife 3 daughters, 6 granddaughters would think that is just about right for 1 shower. (A 2.5 gallon shower head for ~20 minutes). You state that electricity is not reliable, but air compressors also use electricity and as someone that has cheap small volume air compressors to high volume compressors these are energy hogs they are not an efficient way to boost your pressure. A pressure tank is usually used to provide a buffer to the system and reduce the start cycles on the pump. It is obvious you do not want to hear this advice and I will accept the down votes but air over water in a dynamic system will be more costly and more prone to failure. Just as an example I can give dozens of water pump designs used in hundreds of millions of homes but not one example like yours.

Could your idea work, sure it could, but it would require an air compressor and solenoid valves to control the tank pressure for a very limited amount of water between recharge cycles.

A small pump 1/2 horse power possibly smaller could provide the flow & pressure from a holding tank. This is what people in the US do when they have low flow water wells, they pump into a open cistern or tank not pressurized, a pump at the tank pressurizes the system usually comprised of a small pressure tank to reduce the start cycles. A large plastic tank to hold water is not very expensive. I live in a zone that has abundant ground water. There are some areas that the water is deep or they don’t have a good flow so a holding tank or cistern is used not air over water. It is a good question and I up vote it for that but I do not think it is economically viable.

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    A gas (petrol) powered air compressor is an option, but probably not in the $200 range the OP spec'd. – FreeMan Feb 18 at 15:42
  • I had not thought about gas powered compressor, but thinking along those lines a gas powered water pump would be less expensive but that is an idea with unreliable electricity. – Ed Beal Feb 18 at 17:07

This is how it's done in New York City. No air pumps, no water pumps, just gravity. There are complexities in taller buildings that may not concern you if you have only 4 floors in use.

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  • Jay, there is a water pump to push the water up. Every foot of elevation is 1/2 psi but this is an “open tank” not sealed or not a pressure tank. almost every city in the US has one. Since the op doesn't have the height a booster pump would still be needed. – Ed Beal Feb 18 at 17:10
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    Agreed. Equally though there are lots of 6-story buildings with no storage tanks. It obviously depends on the details but OP's situation might be able to use a tank on a pedestal on the roof. Can we agree that a pressurized storage tank for an apartment is more of a Rube Goldberg project than a Home Improvement one? – jay613 Feb 18 at 18:24
  • Jay I was biting my tong trying to not invoke Rube, lol, – Ed Beal Feb 18 at 18:58

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