Water heater pressure relief valve leaking is a very common problem. It is also a very simple problem. If the valve is worn out or damaged, all you need to do is replace it. You need to hire a plumber, water heater expert or a handyman for the job. Just get a new valve, identical to the one you have and preferably of the best quality. Turn off the water supply, drain the water inside the heater, remove the discharge tube, remove the valve and replace it. The job is indeed that simple. You wouldn’t even need any rare handheld or powered tool.
The real problem with water heater pressure relief valve leaking is when replacing the old one with a new valve doesn’t solve the problem. You would notice that the new valve is leaking too. Then the problem is not with the relief valve. It is essentially doing the job it is supposed to. A temperature and pressure relief valve is supposed to let excess water out when it adjusts for the high pressure of the water inside.
As you turn on the water heater, it will heat the water inside the tank and as a result, the water will expand. Water at room temperature has the least pressure. Every relief valve is manufactured in a way to resist up to a certain pressure and temperature. When that threshold is exceeded, the relief valve will leak.
Many homes use a pressure regulator to create a closed system so the water supplied into the home through the mains don’t get flown back and hence get circulated within the plumbing system of the house. This creates additional pressure because the water being heated and hence expanding naturally doesn’t have the ability to expand beyond the inlet of the mains. Had that happened, the water would have kept expanding through the pipes onto the city lines, which don’t have a miniature contained system like your water heater.
The simplest solution to water heater pressure relief valve leaking, when you have already check that it is not the valve, is to get an expansion tank. You can get this expansion tank installed anywhere but connected to the plumbing system. It doesn’t have to be next to the water heater. The expansion tank will allow the naturally expanding water to get accumulated and this will get rid of the excessive pressure on the relief valve. As a result, you wouldn’t experience water heater pressure relief valve leaking.