Neil.Steiner
Member
[Disclaimer: I posted a very similar question at Stack Exchange Home Improvement, but then wondered why I didn't go straight to the experts on this site.]
Do water heater TPR valves fail gradually or catastrophically? A day or two ago, I noticed about a capful of water in the pail below my PTR valve outlet. The only recent change to my system is that I used to have my washing machine hot water faucet connected to a pressure gauge instead of the washing machine, and I instead removed the gauge and reconnected the washing machine hose. And now the pipes give a conspicuous knock when any valve is opened or closed too quickly—the washing machine being the prime culprit.
I opened the TPR valve to test it and wasn't entirely happy with the way it closed, so I opened and closed it again and found that it stopped dripping much more quickly the second time.
I then shut off the water supply to the hot water system (my water heater and my expansion tank), opened all hot water faucets, and checked the air pressure on my expansion tank. The pressure was 28 PSI instead of the original and expected 60 PSI, so I'll have to address that. And the expansion tank is now six years old, so it's probably time for preventative replacement. (Never mind the fact that the water heater must be 25 years old and still kicking, perhaps thanks in part to annual flushes and anode replacements as needed.)
Then I reopened the valve to the hot water system and closed each of the faucets, and the TPR valve spit up some water when I closed the last faucet. I'm not sure what the pressure was the moment the system became closed, but I'm sure it wasn't the 150 PSI that the TRP valve is rated for, nor probably much higher than the 60 PSI coming off the PRV from the water main. But all of the sudden, I'm not sure whether I should suspect the TPR valve or the water expansion tank or both.
I don't know why the washing machine causes the loud noise when its hot water valve opens and closes, nor how the pressure gauge that used to be connected to the system would mitigate that same effect from the cold water valve. Can any of you offer me any insight into what is likely happening?
Do water heater TPR valves fail gradually or catastrophically? A day or two ago, I noticed about a capful of water in the pail below my PTR valve outlet. The only recent change to my system is that I used to have my washing machine hot water faucet connected to a pressure gauge instead of the washing machine, and I instead removed the gauge and reconnected the washing machine hose. And now the pipes give a conspicuous knock when any valve is opened or closed too quickly—the washing machine being the prime culprit.
I opened the TPR valve to test it and wasn't entirely happy with the way it closed, so I opened and closed it again and found that it stopped dripping much more quickly the second time.
I then shut off the water supply to the hot water system (my water heater and my expansion tank), opened all hot water faucets, and checked the air pressure on my expansion tank. The pressure was 28 PSI instead of the original and expected 60 PSI, so I'll have to address that. And the expansion tank is now six years old, so it's probably time for preventative replacement. (Never mind the fact that the water heater must be 25 years old and still kicking, perhaps thanks in part to annual flushes and anode replacements as needed.)
Then I reopened the valve to the hot water system and closed each of the faucets, and the TPR valve spit up some water when I closed the last faucet. I'm not sure what the pressure was the moment the system became closed, but I'm sure it wasn't the 150 PSI that the TRP valve is rated for, nor probably much higher than the 60 PSI coming off the PRV from the water main. But all of the sudden, I'm not sure whether I should suspect the TPR valve or the water expansion tank or both.
I don't know why the washing machine causes the loud noise when its hot water valve opens and closes, nor how the pressure gauge that used to be connected to the system would mitigate that same effect from the cold water valve. Can any of you offer me any insight into what is likely happening?