The drain valve at the bottom of a water heater, which looks like a small outdoor faucet, is used for flushing mineral deposits from the water heater or emptying water from the tank for replacement or repairs.
To drain a water heater using this valve, see How to Drain or Flush a Water Heater. Remember that the water is hot!
Water Heater Drain Valve Problems
Sometimes the water heater’s drain valve won’t work or barely dribbles when you try to use it. Sometimes the drain valve is defective, but most of the time it’s clogged. Mineral deposits, which accumulate over time, consist of lime scale, calcium, and iron in the water. If excessive deposits are allowed to build up inside the tank, they can clog the drain valve when you try to use it.
First Steps in Breaking a Drain Valve Clog
1 Depending upon whether the water heater is gas or electric, turn off the gas valve or circuit breaker that powers it.
2 Connect a hose to the drain valve and run it outside, placing the end of the hose below the level of the water heater. Turn on a hot water faucet somewhere in the house or open the water heater’s pressure-relief valve to break the vacuum inside the tank.
3 Then open the drain valve. If the water runs freely, the valve works. If it doesn’t, it’s probably clogged.
4 If you suspect that the drain valve is clogged, you can try repeatedly stepping on the hose a couple of feet away from the tank to squirt water and air bubbles back into the tank. Hopefully this will break loose the clog. If it doesn’t, please see How to Back-Flush a Water Heater.
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