: I am having a problem with my new hot water heater. The pressure relief valve shoots hot water out of it very frequently. I cannot set a temperature much above the warm setting. Any ideas on what I can do before I call the company on Monday. I am losing a lot of water.
Let me guess......you probably have a pressure reducing valve on your cold water line (probably just inside your foundation wall). If so, I think you may be experiencing "thermal expansion". This is where the water is expanding as it is heating, thus expanding the molecules. Most pressure reducing valves act as a "check valve" and do not allow the excessive pressure to pass back thru it. The T&P relief valve is pre-set for 150# and when the expanding water reaches that pressure, the relief valve starts to "trickle". As soon as any faucet or fixture uses water, even a glass full, the excessive presssure is brought back to ambient level. When the heater goes thru a "heating cycle" the process starts all over again.
This senerio can easily be checked with a pressure gage being connected to the boiler drain at the bottom of your heater. Watch the pressure rise as your heater is heating (you may have to adjust your upper thermostat "higher" to cause a heating cycle to begin.
The cure is to buy a "thermal expansion tank" (probably a 2 gallon size) and install it in the cold water pipe near (or on top of) your water heater. This tank has a bladder that is pre-charged with air to about 40 PSI and the excessive pressure will compress this bladder to hold the expanded water until water is used somewhere or the heating cycle is over. Lowe's and Home Depot carry these "thermal expansion tanks".