How to Replace a Water Heater Drain Valve: Draining Tips

Find out how to use a water heater drain valve for fast and easy draining.  See how to replace a water heater drain valve and drain a tank with a clogged valve. Learn how to fix problems such as leaking, unit not working, and sediment buildup.

Water Heater Drain Valve: Types and How Tos


Drain valve
Brass drain valve (photo:

Two types of drain valves are mostly found on tank-type gas and electric water heaters, made of plastic and brass.

The recommendation is to buy a water heater equipped with the brass drain valve as they are stronger and more durable, while the plastic drain valves are easy to damage, especially around the threads making them more likely to leak. If the water heater has a built-in plastic valve, you might want to replace it with a brass valve.

Some plumbers suggest using the ball valves as these are better and bigger for successful and fast draining and provide hassle-free maintenance.

Some manufacturers, such as AO Smith, utilize a reliable tamper-resistant brass drain valve with the standard size of 3/4″ in almost every water heater.

Why Should I Drain a Water Heater?

There are several reasons why to drain a water heater:

  • Replacing a heater or parts that require emptying the unit.
  • Flushing due to the sediment buildup.
  • Winterizing, prepare your heater for winter by draining the tank.
  • Water heater drain valve leaks.
  • The drain plug is clogged.
  • The drain valve is broken.

How to Drain a Water Heater: Instructions

Before you drain a water heater, make sure that 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 following.

  • 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, so all water can run until it becomes colder (100 F or less).
  • Close the main shut-off valve on the incoming pipe.
  • Open the TPR valve (located on top of the unit).
  • Attach a hose to the drain valve and use the other end of the hose so it terminates 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.

Note that when filling the heater with water again, make sure that the drain valve is closed. It is recommended that the water heater is drained and flushed every 6 months or once a year.

The valve is designed to be installed at a certain height from the bottom of the tank, so there will always be some water left even if you try to drain the unit thoroughly. Water 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.

How to Replace a Drain Valve: DIY Instructions

Plastic drain valve (

Replacing a drain valve on electric and gas heaters is very easy, and it doesn’t require any special tools or skills. It is important to have the water inside the tank cooled so it doesn’t produce any burns. To replace the part, you can either fully or partially drain the water from the tank. The reasons for replacing the valve might be leaking, clogged, or a broken valve.

  • 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 water supply valve located close to the heater. Make sure all the faucets in the house are closed, as the vacuum created inside the tank will prevent water from running out and causing damage.
  • Prepare the new drain valve by applying the Teflon tape or pipe sealer to the valve threads. If the water heater comes with a plastic valve, replace it with a brass or ball valve which is reliable, stronger and can last longer.
  • 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.
  • Quickly install the new valve, turning it clockwise so the heater won’t lose too much water.

Drain Valve Problems and How to Repair

All heaters have a drain plug at the bottom of the unit. Such a location allows you to perform routine maintenance and drain the tank easily. However, there are problems: the valve 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, then there is a problem that has to be fixed.

Did you know that one of the primary services offered by plumbers is repairing plumbing leaks. Contact a Pro!

How to Unclog a Water Heater Drain Valve

When the water heater drain valve is clogged, it is easy to recognize that nothing comes out, water flows sporadically, or trickles instead of a steady stream.

The main reason for blocking the stop mechanism within the valve is the sediment buildup. As the water gets warmer and eventually hot, mineral deposits will start extracting at the bottom of the tank. If there is no regular maintenance, sediment buildup can develop heavily, clogging up the drain valve and affecting the performance and efficiency significantly.

There are a few methods that can be used to fix this problem:

  • Keep in mind that sometimes, when the mineral buildup is not severe, it just takes time for the sediments to be pushed from the water pressure, get loose, and move further through the drain.
  • If the buildup is severe, try to loosen debris by using the stiff wire or screwdriver. Insert the tool through the drain valve, move it back and forth and in a circular motion. Even if you have loose some, the debris can block the valve again, so repeat the process.
  • Instead of the wire, you can use the back-flush method, connecting the garden hose and water faucet and directing the water into the tank, pushing the sediments away from the valve and eventually removing the obstructions.
  • Remove the drain valve (especially if it is plastic) using the instructions from above, and replace it with the 3/4″ ball valve. Use two 3/4″ dielectric nipples to prevent rust. The valve is bigger and stronger, and it will help in the future, preventing sediments from clogging again.

Keep in mind that all these drain valve problems could be prevented from happening by performing the regular maintenance.

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