Actually, it’s called a temperature/pressure relief valve because it relieves excess pressure in the water heater tank.
This can be caused by a malfunctioning gas control valve on the water heater, in which case you will want to have the problem remedied ASAP. Not only does it waste water, but it is also a safety issue. The pressure relief valve is your protection against a water heater catastrophe. Since changing it out requires knowing how to cut and sweat copper pipe, this job definitely requires professional help. As always, we will be happy to come out, look at your problem, and give you a free, no obligation estimate-that’s what we do!