SylvanLMP
EB there are some dirty tricks that old boiler inspectors did to stop a “relief” valve from discharging after a test.
But considering how unscrupulous it is I would only suggest you do the following
Go back to your heater and try the test lever again to see if it seats properly a few pulls STAND aside from the scalding hot water.
Then in the morning call a Licensed Master plumber to not only relplace the T&P but flush out the bottom of the tank and check the flue for proper updraft.
It sounds like your hot water tank was installed and forgotten about like most stumble bums would do with total disregard to ASME/NBBI testing guide lines.
You got to love home centers selling this stuff with no one explaining how to properly check these potential bombs.
