Quote:
Originally Posted by retiredguy123
Typically, the T&P relief valve on a water heater is set to open if the water temperature exceeds 210 degrees Fahrenheit or if the pressure exceeds 150 psi. When the relief valve opens, it doesn't take much water to be expelled to reduce the pressure, maybe a cup or so. So, if you see a small amount of water in the overflow pan under the water heater, it could be that the relief valve has tripped. If the Nova canisters are only designed to handle up to 90 psi of pressure, it is very possible that a defective expansion tank can cause the canister to leak, even if you have a pressure regulator on the water supply pipe to your house. A defective expansion tank will not necessarily caused the water pressure to increase. But, what can happen is that you use all of the hot water in the tank, and then you shut off all plumbing fixtures. This causes the tank to fill up with cold water, and the water heater heats it up causing thermal expansion of the water and a huge increase in the water pressure because the water has nowhere to go. Note that older houses with one or two drippy faucets will not experience this pressure increase, or if your ice maker calls for water while the tank is heating up. Also a very high temperature setting on the water heater and a very cold water temperature will exasperate the problem.
|
And to add to this good information, when Nova came to install my system 4 years ago, before they did anything they checked my hot water expansion tank. The problem is 1) some installers never charge the expansion tank to the water inlet pressure and it fails prematurely and 2) many don't know or ever check the expansion tank. So, it's very possible many of these filter housing failures could be caused by over pressure due to expansion tank problems. But in my house, I regularly check the expansion tank and I pressurized it myself to the water inlet pressure so I know this couldn't have caused my filter housings to show signs of cracking. In addition, as mentioned, only two out of the three filter housings showed signs of cracking. Why was one OK?