The original valve (~5yrs old) started leaking a few months ago, so I tested that I could open it manually and close it to stop the flow. But after the test it kept leaking (at that point pressure should certainly not have been the issue). I replaced it with a part from a hardware store (same length), and the replacement part tests properly: I can open it manually and close it to stop the flow and it doesn't keep leaking. But whenever the gas turns on, it will start dripping steadily. Based on a comment from "temperature pressure valve leaking", I checked whether there is an excess of hot water pressure when I turn on the hot water after the heater has turned off. There isn't. The water pressure is constant.

  • What temperature do you have the tank set to: middle of the range (usually there is a mark to indicate "normal" recommended) or do you have it set higher? – Jim Stewart Oct 30 '17 at 20:32
  • Yes, moderate temperature due to having a toddler. – Matt Chambers Oct 30 '17 at 20:38
  • By simply opening a valve how would you tell if there was "an excess of pressure" after heating a tank of water? The excess would be instantly relieved when the valve was turned on. – Jim Stewart Oct 31 '17 at 10:51
  • Does your water supply system have a back-flow prevent valve (aka a check valve)? The presence of a back-flow prevent valve causes pressure in the hot water system to rise above the water main supply pressure by trapping water in the house plumbing. I think a pressure reducing regulator might also trap water. Some municipal water supply is at a significantly higher pressure (100 psig or higher) than is desirable for a residence (~`50 psig) and residences in those localities have a regulator to reduce the inside pressure. – Jim Stewart Oct 31 '17 at 13:18
  • @JimStewart I referring to the comment in the linked post: "When you open the hot valve at your sink, do you notice a surge of water and then a reduction in pressure? This is a classic sign of high pressure in the system. The pressure builds as the heater heats the water, when you open the valve you release the pressure. For a moment the water will come out at the higher pressure, but then will drop back down to the normal pressure." - I do not see a moment of higher pressure with a fallback to normal pressure. – Matt Chambers Oct 31 '17 at 14:51

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