Electric HW Heater T&P Issue

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Shackatoa

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We have a approximately 7 year old GSW G640TDE. Each winter it is drained and shut off for 4 months. There is a relief valve in the cold water supply line in addisition to the T&P valve on the tank itself. This year when we refilled the tank and turned it on both valves released a steady flow of water when the water reached 120 degrees.

Steps we have taken:

1) Replaced upper thermostat
2) Cleaned out sediment and replaced lower element.
3) Measured the water temperature at faucets and tank. 120 degrees

Other factors (?)

1) We have a well
2) We replaced the kitchen sink faucet with a single handle type and added shut-off below the sink.

We will measure the water pressure today, but what else could be causing the pressure relief valves to blow?
 

Jadnashua

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WHen working properly, only two things can cause the T&P valve to open: over pressure (typically >150psi) and/or over temperature (>210-degrees F). But, once you manually open them to either drain the system or to test them, especially when older, they tend to stick and no longer seal. This can be caused by mineral deposits, or maybe some sand or other grit particles that may have been washed into the lines from the well (or any water supply, doesn't have to be from a well).

As to a pressure relief valve...I doubt your well produces enough pressure to cause it to open, but the same thing, it may be getting old. A typical well system has a pressure tank, and that usually negates the need for an expansion tank, so I doubt you actually need one OR the pressure relief valve.
 

Shackatoa

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WHen working properly, only two things can cause the T&P valve to open: over pressure (typically >150psi) and/or over temperature (>210-degrees F). But, once you manually open them to either drain the system or to test them, especially when older, they tend to stick and no longer seal. This can be caused by mineral deposits, or maybe some sand or other grit particles that may have been washed into the lines from the well (or any water supply, doesn't have to be from a well).

As to a pressure relief valve...I doubt your well produces enough pressure to cause it to open, but the same thing, it may be getting old. A typical well system has a pressure tank, and that usually negates the need for an expansion tank, so I doubt you actually need one OR the pressure relief valve.
Thanks for replying. What is confusing is that water also comes out of the old pressure relief valve tube with is installed in the cold water supply line. Any thoughts?
 

Jadnashua

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Why do you need a pressure relief valve with a well in the first place?

They do wear out eventually. One of the pros may have some other thoughts.
 

Shackatoa

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Not sure why I need a pressure relief valve, but 1 was already installed in the cold water supply line and the other came installed on the HW heater. The well pump is just a few feet from the HW heater, not down in the well. Old farm house.
 

Jadnashua

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Replace the T&P valve, and I'd probably bypass or remove the pressure relief valve on the cold water supply. It might provide a safety release if for some reason your pump motor failed to turn off, but many pumps can't generate enough pressure to damage your plumbing in the first place. If yours can, maybe useful. I don't have a lot of experience with well pressure switches, but they tend to fail by not turning the pump on more often than turning on and staying on, which might make a pressure relief valve useful.
 

Master Plumber Mark

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leave your well alone..... it will not ever over pressure itself in our lifetimes... it simply cannot happen
they usually only have a range of between a low of 30psi and a high of 60psi... why someone put a pressure relief valve on a well is beyond me.......

all you got to do install a new pressure relief valve on the water heater..
. simply replace the leaking one with a new one...

the problem will resolve itself if you just do this simple task.....






sometimes it feels like I am handing a chimp a loaded machine gun....
 

Shackatoa

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Thanks All! I replaced the T&P valve and cold water supply line. I took off the old pressure relief valve in the supply line. IT WORKS!!! I learned so much about hot water heaters from this experience, so it wa worth the effort.
 
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