The temperature and pressure relief valve
Quick answer
The T&P valve is a critical part of your water heater and your plumbing. It stops the heater from exploding or flooding your home by opening if the water reaches 210°F or the pressure goes over 150 psi.
How To Change My T&P Relief Valve
Why they leak
The valve drains water when it senses pressure or temperature is too high. Usually it opens to protect the heater and then won't close completely, which causes a slow leak.
It can easily malfunction, so test it to make sure it works. And find out what made it open in the first place: often the pressure regulator has failed, or the heater is overheating. Fix the cause, or it will happen again.
Replacing it
The valve threads into the tank and usually has a copper discharge pipe soldered to it. Parts are about $35, but you'll need to solder copper. In the video Brandon shows the whole replacement, including a quick lesson on soldering.
If water is leaking where the valve threads into the tank, the tank itself can't be repaired.
Rather we did it?
T&P valve replacement from $195 + parts