08:46PM | 12/16/02
Member Since: 12/16/02
2 lifetime posts
Does anyone have any experience with thermal expansion tanks? My water pressure increases noticeably after the hot water has been running. I don't know how much it increases -- it's not enough to trip the pressure release valve. But I find the increase in pressure annoying and I worry about the wear on pipes and fixures.

How well do they work? Do they keep the pressure pretty constant? I think my pressure regulator is set around 60 PSI. I have seen a Rheem model sold at Home Depot and other places. Are some models better than others? Is there any maintenance required on them?

Thanks for any information you could offer.


05:11AM | 12/17/02
Member Since: 10/15/02
359 lifetime posts
Are you on a well system?


08:21AM | 12/17/02
Member Since: 11/17/02
50 lifetime posts
These tanks work with a high and low limit switch. When the pressure drops below a fixed pressure, typically 20 pounds below the high setting. The pump comes on and tries to refill the tank to the max setting, (usually 45 psi). The problem is the difference between 25 and 45 is substantial when your talking water volume and pressure. Many of the tanks can be reset for 60/40. The difference at this pressure is the same, but you notice it less, because of the lower volume required at the faucet itself. The real problem though, is most tanks are 15 gallons storage. For 15 gallons you get pressure between 25 and 45 psi. But when you have exceeded the timelimit (15 gpm/gpm of faucet) you get pressure at that available by the pump. If the pump cannot produce enough pressure to provide it at 25 psi, it drops down to the pressure the pump can produce. Many times installing a variable speed pump, or a larger expansion tank solves the problem. A variable speed pump produces as much water needed at a constant pressure, a larger tank simply stores more gallons so you can use it longer at a constant pressure.
Another problem, is if the pressure tank fails, and becomes water logged. The diaphram inside the tank can develop leaks and you will loose the pressure quickly, because there is less air to compress. Or the pressure inside of the tank could have been lost and you may have to recharge it. Start with the simplest solution first, check the tank pressure to see what the pressure is. There is a smal valve like on a tire on the top of the tank. Use a tire gauge and see what it is. If its less than 45 add some air.
Good Luck
Plumbing Prof


12:34PM | 12/17/02
Member Since: 10/15/02
359 lifetime posts
Except he is stating his pressure INCREASES, not decreases as the water is running, which is why I asked if he is on a well. If he is then he needs to boost his pressure tank to what the pump is rated at. It sounds like the pressure is set too low on the switch and as the tank depletes his pump kicks in at a higher volume. If he is on city water though, this theory goes out the window.


04:40PM | 12/17/02
Member Since: 12/16/02
2 lifetime posts
Sorry for the confusion. No, I'm not on a well system, just the city water supply. I also meant that the pressure increases *after* the hot water has been running, meaning that the water is off and the water heater is heating it up again. The way I understand it is since I have a closed water system, the pressure regulator doesn't let any water back into the main water supply, the water expands and causes an increase in pressure.

With that in mind, are the kind of tanks you are referring to applicable to my situation? I didn't think there was any pump involved. The tanks I've seen at the home stores are maybe the size of a propane tank for an outdoor bar-b-que and just look like they have a connection for the water to go in and out.


05:33AM | 12/18/02
Member Since: 10/15/02
359 lifetime posts
OK I now understand what your asking. You will need to install an expansion tank on the water heater. They are usually about the size of a propane cylinder and mount on the hot water line. You can find them at any home center. That will solve your problem.
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