Step 2 · Drain the Water Heater Partially
Attach a standard garden hose to the drain valve located near the bottom of the water heater tank. Route the other end of the hose to a floor drain, utility sink, or outside, ensuring the exit point is lower than the drain valve itself. To allow air into the tank and prevent a vacuum, open a hot water faucet at a sink somewhere in your house. Then, fully open the drain valve on the water heater (this may require a flathead screwdriver or a handle). You only need to drain enough water so the level is below the T&P valve you are replacing, not the entire tank.