Water Pressure Question

Factual Questions
21

Without anything mechanical being added I doubt you’d be able to maintain pressure. The city water provides the pressure and if it goes your system will no longer recirculate. Without the feed pressure from the city wouldn’t the water settle in your pipes?

If you can go mechanical can you use a smaller pump to just maintain pressure in your house lines? Have a Pressure Control Valve near the end of your water circuit with a pump to maintain pressure. It seems to me that less energy would be spent in maintaining line pressure vs tank and line pressure.

The easiest method would be to have a drain valve at the tank. Rely on the head pressure to get water to your taps and if the water runs too low for that the valve would enable you to get water from the tank.

22

[QUOTE=kanicbird;]
There seems to be some confusion as to how pressure tanks work, though it has been stated correctly. The water pressure 60psi, compresses air in the tank at a lower PSI till the air in the tank reaches 60psi, then no more water can enter the tank. If the city water supply goes out and you have a working check valve preventing your water supply from backdraining, you have 60PSI waterpressure. As you use your water the compressed air will provide the pressure, but will drop in pressure. So after flushing a toilet you may now only have 55PSI available This would continue till the pressure tank is empty of water and then you will suddenly lose all water pressure (so it may go from 20PSI to 0PSI right away)

As mentioned there is a schrader valve so you could add more air to boost the pressure back up again. In your application you might not want a air bladder at all, or have practically no air in the system. This way your tank is totally full of water, when you want to use the tank add air then (you will need air several times, but it will get you full capacity of the tank. The down side to this is even greater stagnation of the water in your pressure tank (see below)/QUOTE]

[QUOTE= 48 Willys; Huh?? Why would the water no longer be potable? It was clean and is stored in a clean tank. Since the tank’s flow keeps the water in it clean and fresh, why would it get contaminated very quickly?

Also my water meter has a back-flow prevent-er valve in it. My water can not flow backwards out of my meter into my neighbors house. Thus, if I had an installed water storage tank in the water line to the house, it can not drain out into the neighbors piping through my meter. This is a requirement here. /QUOTE]

It’s a big dead end in the line, lots of water with no where to flow. There is no separate outlet and inlet in most tanks, just one pipe that serves both directions. Small variations should provide some exchange with fresh water if you have air in the system, not so much if you don’t.

Additionally if the water does go bad in this pressure tank you need to consider that this bad water may also gently constantly feed into your piping system.

A better design may be a large water holding tank, a small pressure pump and a small pressure tank in a system isolated from your main water supply by a valve that can be turned on and connected in that type of situation.

This assumes the valve works 100%
[/QUOTE]

OK, That is not what I had thought the OP had in mind. I was imagining a non-heated hot water tank installed in the mainline. It would not be a dead end and would have fresh water flowing it at all times. There would be a ball valve on the inlet just like the heated hot water tank.

To be used as an emergency water supply, during a water system failure, the ball valve would be manually closed. One would drain the water out through the faucet on the bottom of the tank that is normally used to flush the water heater. Venting of the tank, so air could replace the water that is drained out, would be achieved by cracking any water faucet.

Yes the back-flow valve may fail. I am very aware of that possibility. If another back-flow valve is installed in series with the one in the meter, then a fail safe system is in effect. How often would two of these back-flow valves fail?

So as to be clear, the system would be laid out so that the inlet from the meter goes through a back-flow valve, then the ball valve, then through the non-heated water heater, then to the house main inlet. Clear as mud??

PS, I just use my hot water heater this way when the water system fails. Yes, the water is hot, but hot water is better then no water.

23

How often does city water fail? I’ve not really heard of such a thing in the US and my limited experience it is the most dependable utility along with natural gas and sewer service. I do remember a few times due to maintenance being told ahead of time that water would be shut off, and if the fire dept needed to open a hydrant pressure would be off, and usually there would be rust in the water, but I didn’t know that some areas had such a issue.

24

A decade ago our 100,00 gal city water tower was replaced with a 300,000 gal one.
Reason was due to a couple new subdivisions being added.
We had wonderful tap water and after the new tower many many complaints were made because of the not so wonderful tasting tap water. after a couple years the city lowered the water level to 200,000 gal level and we again have wonderful water.
Now maybe your city water is foul anyway and a warm reserve of stagnant water wouldn’t be noticed but i sure wouldn’t want any part of it.

25

I believe these kinds of tanks are meant more to even out the pressure from a city system, (such that you don’t notice pressure drops when every body flushes at once during Super Bowl commercials :wink: ), than to provide uninterrupted emergancy water supply.

If you loose pressure completely, your tank would only have enough pressure for few gallons. If you rely on water draining out the bottom, that would only work if your appliances are below the water level of the tank, and even then, only if you lines are perfectly sealed. In a single story home, about half you tank would be above the level of the toilet, but your sink would likely be near the top of the tank, and would loose pressure very quickly.

This setup might work if you could place the tank in the attic, but I would strongly recommend consulting a plumber first to see if this were feasible. There are numerous insulation (exposure to the elements) issues and pressure issues that could arise and you would risk severe damage if you installed an inappropriate tank in such a manner.

26

An inline tank won’t affect the pressure, as mentioned above. My guess is it would circulate well enough to stay potable, but your tap water might taste stale, especially after a decade or two.

The problem is, when the supply pressure cuts out, what provides pressure?

If the answer is an air bladder, fine, up to the size of the air bladder.

If the answer is gravity, that works only if there’s an air inlet of some kind. If not, you’ll get about a cup of water and then zero pressure.

Of course, the air inlet would either have to be manually opened during an emergency (when you’d also close a valve upstream, or risk flooding your garage), or it would have to have some kind of check valve.

Finally, I’d put it before the tee splitting your hot water supply from the cold, if possible. You don’t want to cook with water that’s been in the hot water tank. If you’d ever seen the insides of an old tank, you’d know why.