How to Replace a Water Heater Drain Valve. If you need to drain your water heater and the drain valve isn’t allowing a good water flow, then it’s time to replace the valve. You also need to replace the drain valve, if it’s leaking. In any event, replacing a drain valve on a water heater is a job you can tackle yourself. Follow these steps, and your water heater can be good as new.
CAUTION: Draining your water heater for this procedure may put you at risk of being scalded by hot water.
Please be careful when working on your water heater.
1. Turn the power OFF to the water heater at the circuit breaker (electric heater) or main gas line (gas heater).
2. Fasten a length of garden hose to the drain valve at the bottom of the heater. Put the other end of the garden hose in the nearest floor drain or snake it outside the home.
3. Close the shut off valve at the cold water inlet line.
4. Open the temperature and pressure relief valve at the top of the heater. Now open the drain valve and allow the water to drain. You will probably notice some small white particles (called scale or sediment) during the early stages of the flow.
CAUTION: THE WATER WILL BE HOT………..BE SURE NO ONE IS NEAR THE DRAIN HOSE OR THEY COULD BE SCALDED.
5. When the water stops, close the drain valve and remove the hose. Leave the temperature and pressure relief valve at the top of the heater open for the time being.
6. Remove the old drain valve with a wrench. You may get some additional water draining from the spud. Have some rags handy. Replace with a new drain valve. It is a 3/4 inch National Pipe Thread (NPT) drain valve. You may find one at any plumbing house or home store. Use pipe sealer or Teflon tape to seal the threads. Make sure the new drain valve is in the closed position.
7. Open a hot water faucet somewhere in the home. Open the shut off valve at the cold water inlet line. You will hear the heater start to fill.
8. When you have a steady stream of water from the temperature and pressure valve tube, close the valve; when you have a steady stream of water from the hot water faucet, turn the faucet off.
9. Turn the power ON to the water heater at the circuit breaker (electric heater) or main gas line (gas heater; relight pilot if required). Allow the water heater to recover. Check the drain valve one more time to make sure it is tight.
