How To Unclog a Drain Valve: 7 Ways to Get the Water Flowing

How to Unclog a Drain Valve

If you find that your water heater won’t drain, it is likely a clogged water heater drain valve. This is  generally caused by excessive sediment build up inside the tank. As water is heated, the minerals in the water separate and settle at the bottom of the water heater. If the tank is not drained routinely, the sediment will not only reduce the efficiency of the unit, but can also clog the drain valve to the point that you are no longer able to drain the water heater.

The severity of your clog can vary from a minor inconvenience to a major issue, and left unattended, will ultimately result in the need to purchase a new water heater. This is because the sediment will break down the inside of your tank and create an unrepairable leak.

Determine if Your Drain Valve is Clogged

The first step is to determine if the drain valve is actually clogged.

  • Turn OFF the fuel source to your water heater (Electric: Turn off the circuit breaker / Gas: Turn the on/off control knob to off).
  • Connect a garden hose to the drain valve, and OPEN the valve.
  • OPEN a hot water faucet inside your house (leave open) to eliminate the negative pressure within the tank.
  • If the water drains and turns clear, your valve is not clogged.
  • If the water trickles or does not drain at all, the valve is clogged.

There is a good chance that the water in your tank is hot. If this is the case, you should take safety precautions to prevent being burned. Always wear work gloves and safety goggles when attempting to drain your tank. Also, cool the water inside the tank. There are several ways that this can be done:

  1. Disconnect the gas or electric supply to the water heater and allow it to sit for up to 24 hours.
  2. If your water heater is not completely clogged, drain whatever water you can from the drain valve and leave the water inlet valve open. This will allow cold water to enter your tank and dilute the hot water. The fuel source (gas or electric) should be turned off.
  3. If your water heater is completely clogged, you can open the hot water faucets in the kitchen or bathroom to draw hot water from the tank. Leave the cold water inlet valve open to dilute the temperature of the hot water. The fuel source (gas or electric) should be turned off to prevent the water from reheating.

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How to Unclog a Water Heater Drain Valve

There are a number of different ways to drain a clogged water heater tank, and of course the severity of the clog will determine which method works. We recommend starting with the easiest and working your way down the list.

Remember, the water in the tank is likely HOT, so to prevent burns, follow the safety recommendations outlined above. Before starting, turn the power source to your tank OFF. Electric water heaters: Turn off the circuit breaker – Gas water heaters: Turn on/off control knob to off).

Method 1 – Wait

  • If your drain valve has a minor clog, you could simply wait and see if the pressure from the water will push the debris thru the drain line.
  • Leave the drain valve open with the hose attached. Close the hot water faucet in the house.
  • Wait for an hour or so to see if the tank starts to drain.

Method 2 – Wire Coat Hanger

  • Close the drain valve and remove the hose.
  • It’s a good idea to place a small bucket or a few towels under the drain valve.
  • Use a stiff wire, such as a wire coat hanger.
  • Open the drain valve and insert the wire thru the valve and into the tank.
  • Move the wire in a circular motion to attempt to loosen the debris.
  • If you are successful, the water will begin to flow out of the tank.
  • If you have a good flow of water you can turn the valve off, and attach the hose to finish draining the tank.
  • The valve may clog again before your tank has completely drained, but you can simply repeat the process.

Method 3 – Hose Stomp

  • About 2 feet away from your water heater, step firmly onto the drain hose.
  • If the source of the clog is from sediment, an air bubble will be forced back into the tank and unclog the valve.
  • The clog will often return while draining the tank. Keep repeating the process until your tank is drained.

Method 4 – Back-flush

  • Use a wash machine fill hose, which has a female connection on both ends. 
  • CLOSE the drain valve and connect one end of the hose. Attach the other end of the hose to a nearby washtub faucet (often threaded) or a garden hose (attach the garden hose to an outside faucet).   
  • Turn ON the water to the faucet.
  • OPEN the water heater’s drain valve and allow the water to flow into the tank for 10 to 15 seconds.
  • The water from the hose should push the sediment away from the valve and clear the clog.
  • Turn OFF the water at the faucet, and CLOSE the drain valve. Disconnect the hose from the faucet (leave the hose connected to the drain valve, or replace the hose with a garden hose).
  • OPEN the water heater drain valve, and drain the tank.
  • If the water still won’t drain, your clog may be too severe, or your valve is defective.

Method 5 – Change the Drain Valve

  • It’s possible to change the drain valve while your tank is full of water.
  • Purchase a replacement drain valve (preferably brass).
  • Use teflon tape on the thread of the replacement drain valve.
  • Double check that ALL faucets in your house are CLOSED. This will create a vacuum in your water heater and prevent the water from “pouring” out.
  • Place a bucket and towels under the drain valve.
  • Use an adjustable wrench to loosen the drain valve.
  • Slowly unscrew the drain valve. Be prepared for some water to pour out of your tank.
  • Even if your tank is clogged, you will most likely have some water escape. If the issue is a faulty drain valve, you most certainly will have water.
  • Immediately insert the new drain valve. This should only take a few seconds.
  • Connect a garden hose and drain your tank.

⇒ If you are going to go thru the effort of changing the drain valve, we recommend changing it to a ball valve (method 6). The majority of the steps are the same, and you will never need to worry about your drain valve clogging again.

Method 6 – Change the Drain Valve with a Ball Valve

  • A ball valve is much larger than the standard drain valve. By replacing your valve with a ball valve you will not only unclog your tank, but also prevent sediment from clogging it in the future.
  • Purchase a brass 3/4″ ball valve, and two 3/4″ dielectric nipples. (The nipples are coated with plastic to prevent rust). Each nipple will attach to one side of the ball valve.
  • Use teflon tape on the thread of the nipples that screw into the ball valve.
  • Keeping in mind, that the handle of the ball valve should open AWAY from the tank, use teflon tape on the second side of one of the nipples. (Only 3 of the 4 threads on the 2 nipples will be lined with teflon tape).
  • Double check that ALL faucets in your house are CLOSED. This will create a vacuum in your water heater and prevent the water from “pouring” out.
  • Place a bucket and towels under the drain valve.
  • Using an adjustable wrench, loosen the drain valve.
  • Slowly unscrew the valve. Be prepared for some water to pour out of your tank.
  • Even if your tank is clogged, you will most likely have some water escape. If the issue is a faulty drain valve, you most certainly will have water.
  • Immediately insert the new ball valve. This should only take a few seconds.
  • Connect a garden hose and drain your tank.
  • Once your tank has drained, you should either replace the ball valve with a regular valve or remove the handle for safety. The handle could inadvertently be opened and drain your tank, creating water damage and/or serious burns.

Method 7 – Relocate Your Tank

  • This method is generally used if you are planning on replacing your water heater.
  • Disconnect the plumbing.
  • Disconnect the power source.
  • Use a hand truck to roll your water heater outside.
  • Carefully, lay your water heater on its side and drain the water from the top of the tank.