Re: water heater pressure relief
Posted by Charlie on January 31, 19101 at 16:38:47:
In response to Re: water heater pressure relief
Let's try this based on physics 101, lathough I'm sure someone will come back with an experienced based answer. When the element comes on, the water expands. The pressure is transmitted uniformly, so the location should not be an issue. Now, there has to be the capability for expansion or else the pressure will rise very fast, even from a small amount of expansion. The expansion can be taken up either back in the water system feeding the heater, or downstream from the heater. For example, the airspace in my water tank (fed from a well) would be where it would go in my system. Or it could go out to the supply. The only thing that could stop this would be a check valve somewhere between the supply and the heater. My guess is that you have one and that that is the problem. However, if you have an airchamber behind the faucet, I would think that that could also absorb the expansion. So either you don't have one, or it is full of water. Well that's as far as I can get with basic physics.

: I have a small point-of-use (Ariston) water heater in my darkroom. This is my second one, actually. My problem is that, within a matter of weeks after installation, the pressure relief valve screwed into the top of the unit begins to leak every time the element comes on. My theory is that these relief valves are designed to be installed at a greater distance from heating elements, and that it is reading the temperature of the element (it begins leaking very quickly after the heating element comes on and does so even if the heater is only set to "warm"). Would it be Kosher to try installing a pipe nipple or bushing that would put a little more distance between the probe and the element?

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