Water Heater Drain Valve

Draining water heater and
how to replace a drain valve

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Find useful info and tips when replacing a water heater drain valve, explore the drain valve problems, types, how to use, how does it work...


Water heater drain valves are made of plastic and brass. The valves can be found on both gas- and electric-powered units. Recommendation is to use one made of brass as they are more durable with better quality while plastic drain valves are easy to damage especially around the threads and are more likely to leak.

AO Smith heaters are, for example, equipped with a reliable tamper resistant brass drain valve. The standard size is 3/4".

Ball valves are also an option for successful draining, and they are recommended from plumbers for better maintenance.

How to unclog the water heater drain valve

water heater drain valve made of brass

It is easy to recognize when the water heater drain valve is clogged as the water flows sporadically or trickles instead of a steady stream.

The main reason for blocking the stop mechanism within the valve is probably the sediment build-up. One of the solutions to unblock the valve is to clean it under the pressure, but if the procedure doesn't work, this is what you should do:

  • Open the TPR to let the air into the tank.

  • Take a small gauge (thin) wire (i.e. coat hanger) and poke through the drain plug opening to eliminate any obstructions.

  • If the above action is not helping, replace the valve.

The valve is designed to be installed on a certain height from the bottom of the tank, so there will always be some water left even if you try thoroughly to drain the unit. Water that is left at the bottom of the tank will contain most of the harmful and corrosive particles, which can again clog the drain valve. This is why the recommendation is to flush the whole system and remove those deposits.

Why draining

There are several reasons why to drain the water heater:

  • Replacing a heater or component parts that require emptying the unit.

  • Flushing due to the sediment build up.

  • Winterizing, prepare your heater for winter by draining the tank.

  • Water heater drain valve leaks.

  • Drain plug is clogged.

emergency plumber

How to drain water heater

Before you drain the water heater make sure the water inside the tank is not hot. The best will be if you turn the unit off for a few hours and after that perform the action below.

  • Shut the electricity off at the breaker to your electric unit or turn the gas control valve to pilot position or thermostat dial to OFF, if the unit is on gas.

  • Open nearby hot faucets and leave them open. All water to run until it becomes colder (100 F or less).

  • Close the main shut-off valve on the incoming pipe.

  • Open the TPR (located on top of the unit).

  • Connect a hose to the drain valve and use the other end of the hose to terminate to an adequate drain or outdoors.

  • Make sure all the connections are tight and the flow is directed away from people.

  • Open the drain valve to allow the water inside the tank to flow out.

  • When the heater is drained and the flow stops, disconnect the hose from the valve and close it.

When filling the heater... close the water heater drain valve, located at the lower front of the unit, by turning the handle clockwise. It is recommended that the tank is drained and flushed every 6 months or a year.

Draining and flushing is different. Draining means that you are shutting the supply off and then opening the drain.

When flushing the unit, connect the discharge hose to the drain valve and then open it with the incoming water still on. The pressure will force the deposits out of the drain as well as having the incoming water swirl the contents around, to loosen them up.

How to replace a drain valve

To replace a drain valve on electric and gas heaters is very easy. It is important to have the water inside the tank cooled off. To replace the part you can either fully or partially (below) drain the water.

  • Turn the power off at the circuit breaker if the heater is electric or turn the gas valve to pilot if you have a gas unit.

  • Close the main supply valve located close to the heater.

  • Prepare the new ball valve by applying the Teflon tape or pipe sealer to the valve threads.

  • Put the bucket below the valve to collect the exiting water.

  • Unscrew the old water heater drain valve by using the adjustable wrench or large groove-joint pliers.

  • Due to the buildup pressure inside the tank, you might have a rush of water once you remove the old valve.

  • Let the small amount exit.

  • Quickly install the new valve, turning it clockwise so the heater won't loose too much water.

Drain valve problems

All heaters have a drain plug at the bottom of the unit. Such a location allows you to perform a routine maintenance and drain the tank easily. But there are also problems... they might be damaged or leaking.

If there is a missing drain valve it may be difficult to get the sediment deposits out of the bottom of the tank. If the valve is damaged it may not be able to operate. If it is leaking than there is a problem that has to be fixed.

(All pictures are courtesy of Amazon.com)