Every water heater, whether electric or gas, needs a temperature and pressure relief valve, because without one, it could begin to leak or even burst. The T-and-P valve, which is located on the top or side of the cylinder, opens and discharges steam or water once the temperature or pressure exceed preset limits. If your valve is dripping, which may be a indication that it’s doing its job. The temperature or pressure in the cylinder may be too high, and the valve may be going to open. A few straightforward tests can help you determine what is what.
Run hot water from the faucet nearest the heater for about a minute, or till you’re sure it has reached its highest temperature. Partially fill a cup and then measure the temperature with a thermometer. It should ideally be under 200 degrees Fahrenheit. If it’s more than that, the valve may be going to open, because most are set to open at 210 degrees Fahrenheit.
Check the pressure of your water system with water pressure meter. Screw the meter on a basement hot water faucet and turn on the faucet all the way. The reading should be between 60 and 80 pounds per square inch. If the value is close to 150 psi, which is the pre-set threshold for the majority of valves, then the T-and-P valve is dripping because it’s going to open.
Keep the valve on the faucet and empty the cylinder at least halfway by running a bath or taking a shower. Watch the valve as the water in the cylinder reheats. It might reach values greater than 80 psi, even if the system pressure is usually less than that, because of thermal expansion. If so, which could possibly be the cause of the drips in the T-and-P valve.
Test the valve itself to make sure it’s functioning correctly. Stand clear of the opening if the valve is not connected to an overflow tubing. Lift the rocker arm on top of the valve. Water should come out. When you release the arm, then it should snap back down and water should quit flowing. If it doesn’t snap down instantly try lifting and releasing it a few times to loosen it. If it doesn’t lift, the valve needs replacing.