Water Heater Pressure Relief Valve

Mine was doing exactly what yours is doing, so I went to Home Depot and bought a new one and replaced it. Easy repair!

I thought mine was bad too. Read your instructions, according to the instructions a small drip is normal. At least that's what mine say..

Couple of things going on......

When water is heated it 'swells'. That is what 'air pocket' in top of WH tank is for......allows for the water to swell without a large increase in pressure. Water can not be compressed (air can) so without air pocket pressure increases enough to cause T&P Relief valve to 'weep'

Air pocket is normally established just by filling WH but can be lost over time.
Reestablish air pocket by turning water supply off, open faucet hotside to relieve pressure, open T&P Relief valve via lever and then let it snap close when water stops running out, close faucet, turn on water supply.



Over time T&P Relief valve seat will build up deposits especially when allowed to weep. As deposits build up more weeping, ore deposits etc.
Can be cleared by opening T&P Relief valve with water supply on and allowing water to blow thru valve then letting valve snap close. Repeating several times.

And then......
Sometimes due to age, amount of deposits etc. it's just better to replace T&P Relief valve. When doing so it can be easier to remove exhaust duct work so accessing valve is easier.

Flip the little lever up and down a couple of times..this might clear it if there is some calcification.

Also make sure there is an air pocket in the tank:

Water Heater Air Pocket:

Shut off the water supply, open the relief valve until water stop coming out, close it, turn the water supply back on.
This will reestablish the air pocket in the water heater, giving the water some place to expand to when it is heated.

I would work it opened and closed a few times to see if it reseats itself. Do it with water connected so it will flush itself. But be careful if the water is hot. Better to do it with water cold.
Not uncommon for one to leak. But pretty simple to replace it it continues to leak.