Can You Replace Water Heater Drain Valve Without Draining?

If your hot water heater’s drain valve is clogged or leaking, you will need to replace it to prevent scalding accidents or water wastage.

Since a tankless water heater does not have a hot water reservoir, you do not need to drain to replace the drain valve. On the other hand, a storage tank water heater has a hot water reservoir; therefore, you will need to drain.

Either way, the process of replacing a water heater drain valve is quite straightforward and easy to do. You can DIY with easily accessible tools or hire a plumber.

The DIY Procedure for Replacing a Drain Valve

When it’s about replacing a water heater drain valve, the first step is to fetch a new drain valve. You can buy from your reliable traditional hardware or order online.

Aside from plastic valves, you can settle for brass or composite valve. However, the best alternative is brass because it can withstand high temperatures. More also, a brass valve lasts longer than its cheaper plastic and composite counterparts.

Below we discuss a step-by-step process for draining a tankless and a tank water heater. But first, gather all the necessary tools.

What You need

How Do You Replace a Water Heater Drain Valve Without Draining?

This approach works when you have a tankless water heater. So, the only water you’ll deal with is the little that’ll flow from the pipe. Here’s the how-to:

  1. Turn off the water supply to the tankless heater and open the faucet closest to the water heater to release pressure or any water in the drain lines
  2. Turn off the gas valves for gas water heater or power for electric water heaters
  3. Prepare the new drain valve by wrapping Teflon tape around it (at least 6 times) and place it within easy reach
  4. It’s essential to release pressure from the heater. To accomplish that, place a small bucket beneath the valve and allow water to flow for a few seconds
  5. Once fully drained, use the wrench to turn and twist the old valve until you bring it out
  6. Lastly, fix the new water heater valve. While at it, apply some considerable pressure to ensures that the replacement part fits well.

Replacing a Water Heater Valve by Draining the Tank

This method works for both gas and electric tank style water heaters. Ensure to completely drain the reservoir tank and be careful while doing it to prevent scalding.

  1. Turn off your power or gas supply to the water heater
  2. Close water heater water supply. Note that your water heater system has a faucet that supplies cold water. Be sure to turn it off. Also, there are water supply pipes at the top and bottom of the heating system. Close those too
  3. Then comes the draining step. Although you can drain the heater via the hot water faucet, it’s not the best option. Instead, connect a garden hose to the tank
  4. Direct the flowing water to either a drain or the floor using the other end of the hosepipe
  5. There is a TPR valve at the top of your water heater tank. You’ll need to open it to release the pressure inside, which helps drain the water
  6. Allow the tank to settle for a few minutes after draining it completely for any heat to cool off. A 15 minutes wait is sufficient if you have a big water heater
  7. Once the water heating system cools off, it’s now time to replace the valve: turn the drain valve in an anticlockwise direction, then pull it out using a range
  8. Next, get your replacement part and fix it. Turn it in a clockwise direction while pushing it in to ensure it sits inside the slot properly
  9. To avoid dealing with a leaking water heater, ensure to wrap the valve’s threads in a plumber’s tape
  10. After fixing the valve, it’s time to turn on the water supply for the tank to fill up. Do that by opening the cold water supply tap inside your house
  11. Allow the cold water to flow for a few minutes before turning on the heater’s hot water faucet
  12. Now the tank is already full, so you can turn on the power supply and allow it to ignite to heat the water
  13. Lastly, be sure to listen to the heating system. A whistling sound is an indication of leaking valves. You’ll need to turn off the water heater and investigate all the visible valves. Otherwise, the system is all set


So, can you replace the drain valve on a hot water heater without draining? From the above two options, the simple answer is “Yes” for tankless water heaters but “No” for storage tank water heater. It is an easy and cheap DIY procedure. Be cautious and follow the steps to prevent scalding.


Can you still use water if the water heater is leaking?

Contrary to popular belief, it’s safe to shower when your water heater is leaking. However, it’s vital to fix the leak quickly to avoid severe incidences like tank explosions.

Why is my water heater drain valve leaking?

The most common causes of leaking valves are:

  • Loose water lines connection caused by normal wear and tear
  • Broken drain valves, temperature valves, and pressure relief valves
  • Corrosion or cracks in the tank resulting from sediment build-up

How often should you drain your water heater?

An annual or bi-annual schedule works just fine. However, it pays to drain the water tank every few months if the local water supply has high mineral content. Also, you can have a plumber help you to flush the tank when they visit to check on complex issues like a malfunctioning anode rod.

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