How to repair a clogged water heater drain valve

April 20, 2017

Time: A few hours
Frequency: As required
Difficulty: Easy to moderate
Tools: Drain hose, gloves, goggles, towels, wire clothes hanger and/or screwdriver, double-female garden hose coupler

How to repair a clogged water heater drain valve

Is the hot water in your home not hot enough? Are you finding sediment in your faucets or are you shivering through a cold shower? Discover how to tell if your water heater drain valve is clogged and if it is, how to fix the problem in a few easy steps. [Photo credit:]

Water heater basics

Cold water enters your water heater by a cold-water supply pipe, heats up, and then is carried by a hot-water delivery pipe to household fixtures and appliances such as your sinks, showers, dishwasher and washing machine. The most common type of hot water heater is the storage tank type. It may be electric, gas- or oil-fired.
Good to know!

If you’re looking to replace your water heater, consider a high-efficiency model. At up to 50 percent more energy-efficient than older models, they help to reduce energy costs and greenhouse gas emissions.

Step 1: Understanding the drain valve

Water heater tanks are low maintenance and reliable but, over time, hot water tank problems may occur. One possible issue is a clogged drain valve.

  • The drain valve is located at the bottom of the tank and looks like a small faucet.
  • It’s only used when you need to flush mineral deposits from the water heater or when emptying water from the tank for replacement/repairs.
  • When the drain valve becomes clogged, the unit cannot deliver hot water effectively.

A faulty water heater drain is often caused by the accumulation of mineral deposits over time (lime scale, calcium and iron). These deposits collect at the bottom of the tank and can:

  • Clog the drain valve.
  • Form a coating that diminishes the transfer of heat from the burner to water.
  • Break free and clog faucets and pipes.

Good to know!

It’s a good idea to periodically flush or drain your water heater. This removes deposits and keeps the water heater working efficiently. Aim to do this every year or two, but check your manufacturer’s instructions for specific recommendations.

Step 2: Check if the valve is clogged

Sometimes the drain valve is defective but more often it’s simply clogged. To check:

  • Turn off the water heater. (For electrical, turn it off at the circuit breaker. For gas, use the on/off control knob).
  • Attach a drain hose to the drain valve.
  • Open the drain valve and begin to drain the tank.
  • Next, open the pressure relief valve on top of the water heater, or turn on a hot water faucet in your home; this will eliminate the negative pressure in the tank and allow it to drain.
  • If the water drains and runs clear, the problem is fixed. If the water still trickles out or doesn’t drain at all, the valve is clogged.

Good to know!

The water tank is hot so it’s a good idea to wear goggles and gloves for protection. You should also let the water heater cool for a while after disconnecting the gas or electric supply.

Step 3: Unclogging the drain valve

There are a number of methods you can try to unclog a drain valve.
Always make sure the power source is turned off and attach a drain hose to the drain valve if you haven’t already done so.
Method 1 – Wait it out

  • Leave the drain valve open and the hose attached. Close the hot water faucets in the house.
  • Wait an hour or two to see if the water pressure pushes the sediment out and the tank starts to drain.

Method 2 – Try a wire coat hanger

  • Close the drain valve and remove the hose.
  • Open the drain valve and insert a wire coat hanger up the valve and into the tank. (You can also try a screwdriver.)
  • Swirl the wire around to loosen the debris.
  • If this works, the water will begin to drain. Turn the valve off, re-attach the hose and finish draining the tank.
  • If the clog returns before your tank has completely drained, repeat the process.

Method 3 – Step on the drain hose

  • Step firmly on the attached hose a couple of feet away from the tank. This forces an air bubble back into the tank. If there is a clog from sediment, this will temporarily dislodge it.
  • The clog often returns, so keep stepping on the hose until the tank is drained.

Method 4 – Back flush
Use a two-sided female coupling washer hose.

  • Close the drain valve and connect one end of the hose.
  • Attach the other end to a nearby washtub faucet or a standard garden hose (which you then must connect to an outside faucet).
  • Turn on the faucet.
  • Open the drain valve. Let the water flow into the tank for 10–15 seconds.
  • Water should flow into the water heater, pushing sediment away from the valve and clearing the clog.
  • Turn off the water at the faucet and close the drain valve.
  • Unscrew the hose from the faucet. Leave the hose connected to the drain valve.
  • Open the water heater drain valve again and drain the tank.

Of course, it’s possible you may actually have to replace the drain valve, or even your water heater. But with the simple methods discussed here, you can try unclogging your drain valve first before escalating to more difficult and costly solutions.

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