Water Heater T&P Valve

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ncg45

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I have been noticing some water coming from the gas water heater pressure relief pipe (outdoors). Started as a few drops occasionally, but now I'm noticing more water leaking. Do the T&P valves ever go bad? Coincidentally a friend gave me a brand new one that he bought, but never used. I think I might try switching the old valve out and see what happens.
 

Reach4

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I have been noticing some water coming from the gas water heater pressure relief pipe (outdoors). Started as a few drops occasionally, but now I'm noticing more water leaking. Do the T&P valves ever go bad? Coincidentally a friend gave me a brand new one that he bought, but never used. I think I might try switching the old valve out and see what happens.
T+P valves do go bad. There is a test lever that you should check to see if it makes water flow, and then water stops when you release the lever.

However dribbling out is most commonly because the thermal expansion tank is not working right, or you don't have one and need one. After a hot shower etc, if you stop using water, and the water pressure rises to 150 psi because of thermal expansion, the T&P valve is supposed to release water. Odds are, that's what is happening in your case.

A pressure gauge could let you see the pressure rise.

By the way, are you real? Less-skeptical people will think that is an odd question.
 
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WorthFlorida

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T&P opens at 150 PSI, or temperature at 210 degrees. Your leak is probably from too much pressure but the seal that opens can deteriorate and start to weep. It just doesn't open at 150 PSI, it may start to open at a lesser pressure. As Reach suggest do get a pressure gauge with a garden hose connection. They are low cost ($10) and handy to have. Also note that thought Georgia doesn't get very cold temperatures, the inlet water temp does drop in the cooler days, therefore, the water expands more than summer time when heated to the set temperature.

https://www.homedepot.com/p/Watts-3-4-in-Plastic-Water-Pressure-Test-Gauge-DP-IWTG/100175467
https://www.watts.com/resources/references-tools/t-and-p-relief-valves

watts-water-pressure-regulators-dp-iwtg-64_145.jpg
 

ncg45

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T&P opens at 150 PSI, or temperature at 210 degrees. Your leak is probably from too much pressure but the seal that opens can deteriorate and start to weep. It just doesn't open at 150 PSI, it may start to open at a lesser pressure. As Reach suggest do get a pressure gauge with a garden hose connection. They are low cost ($10) and handy to have. Also note that thought Georgia doesn't get very cold temperatures, the inlet water temp does drop in the cooler days, therefore, the water expands more than summer time when heated to the set temperature.

https://www.homedepot.com/p/Watts-3-4-in-Plastic-Water-Pressure-Test-Gauge-DP-IWTG/100175467
https://www.watts.com/resources/references-tools/t-and-p-relief-valves

watts-water-pressure-regulators-dp-iwtg-64_145.jpg
In fact, I do have a water pressure gauges. It's reading 80 PSI which is higher than I remember it reading last time I checked, when I installed an expansion tank and matched bladder pressure to water pressure - 50 PSI. Pressure regulator in house is original and is 30 years old. Might need replacement (??) Is 80PSI excessive for house with copper plumbing? TIA
 

Reach4

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In fact, I do have a water pressure gauges. It's reading 80 PSI which is higher than I remember it reading last time I checked, when I installed an expansion tank and matched bladder pressure to water pressure - 50 PSI. Pressure regulator in house is original and is 30 years old. Might need replacement (??) Is 80PSI excessive for house with copper plumbing? TIA
Two different pressures to talk about. If that 80 psi is not after you have been heating water without using any water, that probably indicates that your regulator (PRV= pressure reducing valve) needs replacing or rebuilding.

If that is only after using hot water without using other water, even 100 or 120 is not too much.

The pipes will not be harmed by well over 150.
 

Bannerman

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Excessive pressure may occur for 2 main reasons. As your home is equipped with a pressure reducing valve (regulator), higher pressure could be leaking through the valve if it is not functioning properly.

A pressure reducing valve will be commonly utilized when the city's water main pressure is 80 psi or above. You said your 'regulator' is 30 years old so it may now require repair or replacement if it is no longer reducing to your 50 psi setting and is not maintaining that pressure reliably.

A second rason for higher pressure is a pressure increase occurring downstream of the PRV. This is most often caused by thermal expansion occurring within the water heater when cold water expands while heated.

A pressure increase caused by thermal expansion will usually occur after hot water has been consumed followed by a period of no water use. The pressure will then gradually rise but as you said your home is already equipped with a thermal expansion tank, unless the bladder inside is damaged, the capacity inside the tank should provide sufficient space to absorb water expansion so any additional pressure will typically remain within approx 10 psi of the PRV setting.
 
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