How to Flush a Water Heater – The 10 Step Guide

(Last Updated On: April 13, 2020)

I had just turned off my TV after watching a horror movie the other night and I heard rumbling sounds coming from the basement. I was trembling in fear but somehow managed to gather some courage to check it out, despite picturing all sorts of scary things that may await me. As I walked down the stairs, the sound got louder, and both to my relief and dismay, I realised the sounds were coming from my water heater. It didn’t sound good, so I switched it off and went back upstairs. I opened my laptop and started searching for a plumber who could fix this issue. Then I remembered that it was Sunday and finding a plumber on Sunday is like Marlin searching for Nemo in the ocean.

Water heaters aren’t on the top of any homeowner’s mind until something goes wrong. Among all types of household everyday jobs, flushing a water heater gets overlooked most of the time. It never really occurred to me until I heard the strange noises coming from my own water heater.

The explanation behind the weird noises, is due to sediment build up inside the water heater. The best bet to extending the life of your tank hot water heater is by doing an annual flush or semi-annual flush if you have hard water.

What does a water heater flush do?

Flushing a water heater helps you to clear out the chunks of sediment inside your water heater. It helps extend the lifespan of your water heater as well as the efficiency. It can also remove weird odors that may be coming from the hot water. It reduces the energy cost as the water heater runs efficiently. And, of course, you also won’t have to hear any creepy rumbling noises in the middle of the night after watching a horror movie!

Is sediment in a hot water tank dangerous?

Yes, sediment in water heater can decrease efficiency. As sediment builds up in the water heater, it creates a new layer between the heating element and the water. This layer gets thicker with time which reduces the amount of water being heated in the container. This layer also increases insulation which makes it more difficult for the heating element to heat the water, which in turns causes energy waste and increases your expenses. This sediment also reacts with the container and harms it in such a way that it can eventually start leaking out hot water. This can cause trouble if you don’t clean or flush water the heater sediment at least once a year.

How much does it cost to flush a water heater?

Most contractors say that on an average a plumber would charge at least $80 to $100 to flush a water heater. You can also do it yourself for $0. $100 can almost cover a Netflix subscription for a year, so you can watch even more scary movies!

How long does it take to flush a water heater?

In general it takes about 20 – 30 minutes to drain your water heater. But to clean it properly you may have to fill it up again and repeat the task 2 to 3 times. This means that it may take around two hours for you to flush a water heater and remove all the sediment. It may consume more time if your container is a large one. So, the debate is over…Size does matter!


Equipment Needed to Flush a Water Heater

Garden Hose

You will need a garden hose to pump out the water from the hot water heater tank, which most people with a yard already have, so no extra costs here.

Clean Bucket

A clean bucket will help you to check the cleanliness of the water that you’ll drain from the water heater. Make sure the bucket is white or very light in color so that you can easily identify the amount of sediment particles present in the water.


Patience is not equipment but ability. You’ll need this ability as you may have to repeat the cleaning process several times for up to two hours to flush the water heater precisely.


Steps to flush a water heater

1. Turn off the heater

The first thing you need to do is to turn of the heating element of the water heater. It is actually the thermostat of the water heater. Change it to pilot mode so that the water in the water heater starts cooling and doesn’t continue to get hot. This will keep you safe from getting burned. If you have an electric heater, then switch off the circuit breaker that is providing current to the water heater.

2. Close the gas valve

Now, close the gas valve. This will stop any gas entering the heating element and the water heater will stop heating the water. You may not have to do this step if you decide to turn the thermostat to pilot mode.






3. Close the cold water valve

Now, turn off the cold water valve. Turning off the cold water valve will stop any water getting stored inside the tank while you’re flushing. Otherwise, you’ll find yourself flushing the water out of the container but the water will keep coming and coming. This will not only waste water, but will try your patience.

4. Turn on the hot water tap of the sink

Open any hot water tap of the sink, shower, or laundry in your home so that pressure gets created inside the tank and the water flushes at a good rate. It will stop the formation of a vacuum and will keep the flow of draining water okay.

5. Open the pressure release valve

The pressure valve actually helps you let out the gas which has built up inside the tank. Opening the pressure valve will make the water flow easier. Make sure you place a small bucket below the pressure valve pipe as hot water may rush out of it as soon as you open it.

6. Connect the garden hose to the drainage spigot

Here is where the garden hose comes into play. Connect it to the drainage spigot of the hot water heater tank. But before you turn the spigot on, make sure the hose pipe leads to a safe place like a drain or any other place outside your home where the hot water coming out won’t cause an issue.

7. Turn the spigot and drain the hot water out

When you believe it is safe to drain the water out of the tank, release the spigot or turn it on. This way the water will start draining out of the container.

8. Close the spigot turn on the cold water valve

Wait for 20 to 30 minutes until the tank is empty. Then turn the spigot off and turn on the cold water valve. The water will start filling up the water heater with a pressure so high that it will start breaking the bonds of the sediment and they will become smaller chunks. Flushing out this water will properly clean the water heater.

9. Open the spigot and flush out the water

When you think the water heater is half full, turn on the drainage spigot again to flush out the water. Use a bucket and fill it up with the water coming out of the water heater to examine the clarity of the water.

10. Keep repeating the process until the water is clean

Keep repeating the process of filling up the tank with cold water, draining it 2 to 3 times and keep examining the water each time using that bucket. When you see that there is little to no sediment left in the water then you know that the water heater flush is complete.


Things to do after you’re done with flushing a water heater –

  • Close the spigot and remove the hose
  • Fill up your tank by turning on the cold water valve
  • Close the pressure relieve valve before water in the tank reaches it
  • Turn on the tap of any sink of your house to release the gas out of the system
  • Turn on the gas valve
  • Turn the thermostat on and choose your desired temperature
  • Wait for 20 to 30 minutes and open any tap of your house to ensure that hot water is coming out properly.

Good job on the hard work!  You have now flushed your hot water heater all by yourself, saving money as well as your water heater. You’re also free of any creepy rumbling noises.

Unfortunately, flushing your water heater regularly is important for both tank and tankless water heaters, so even though there are many benefits of purchasing a tankless water heater over a tank version, this is not one of them.



Tankless Reviews was created with the goal of helping people to understand the benefits and practical knowledge related to tankless water heaters. After purchasing my very first tankless heater years back, I realised that other people needed to hear about the incredible money-saving ability of this household item, and wanted to share my lessons with you!