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How Long Does It Take to Drain a Water Heater? – Detailed Answer

Writen by Ronald Brown

Fact checked by Natalie Bridges

how long does it take to drain a water heater

Draining your water heater is part of its routine maintenance. It helps eliminate sediment build-up from your residential appliance. Moreover, it will prolong the lifespan and ensure the maximum efficiency of your heater.

Most homeowners drain a water heater every six months to 12 months, but the question is “how long does it take to drain a water heater?” Typically, you can empty your water heater during a time period of 5 to 15 minutes.

But the cleaning duration still varies depending on several factors. Read below to learn more about them!

Table of Contents

Factors That Affect How Quick You Drain Your Water Heater


Here are some factors that significantly impact how fast a water heater drains :

1. Tank Size

The tank size of your water heater unit determines how much water it can store and heat. The general rule of thumb is that the larger the tank, the longer it takes to drain water.

How long does a 40 gallon water heater take to drain? Most 40-gallon units incorporate a high-pressure valve, so you can expect it to drain in just about 4 minutes.

Compared to a 60-gallon unit, which drains longer (an hour or so), it is easier to drain a 40 gallon water heater.

2. Sediment Build Up

Sediments are the number one killer of storage-tank water heater systems. They are not something you cannot ignore; a sediment build-up can cause slow water drainage and leakage. More sediment means your water heater will take more time to drain.

3. Drain Valve Type and Size

Most plumbers use a brass valve as it is more robust and durable than its plastic counterparts. Brass valves come in two variations: ball valves and gate valves. Ball valves are more expensive, but they allow water to drain quickly.

As for the diameter, the conventional size of a drain valve for most water heaters is ¾ inch. Obviously, a drain valve that’s 1 inch or bigger will let water out more quickly.

4. Water Pressure

Generally, a water heater can drain at a speed of 9 GPM – 17 GPM. But depending on the domestic water pressure and the type of drain hose used, the water flow rate can change.

For instance, if you drain a 50 gallon hot water heater and your plumbing system at home allows the water to flow at 10 GPM, you can expect to empty your tank within roughly 5 minutes.

How to Drain a Water Heater System?


Whether you have a traditional gas water heater or an electric water heater, all models have a drain valve to empty the tank and release a substantial amount of naturally occurring minerals.

Draining your water heater system includes preparatory work, water draining, and a post-cleaning process. If you have a decent water flow at home, the draining stage alone could take less than 15 minutes, but given all the prep work and post work, it could take a day to finish the task:

Stage 1: Prep Work

You cannot just drain your entire water heating system without preparation. The steps for this process include :

  • Prepare the tools and supplies to drain the water heater properly.

You would need to prepare the following :

  • Garden hose with rubber gasket (to prevent leaks)
  • Adjustable wrench or Flat-head screwdriver
  • Bucket
  • Turn off the electric supply of your water heater.

If you have a gas water heater, you need to disable the gas line by turning the shut-off valve clockwise (to pilot mode). For an electric model, flip its circuit breaker.

You should turn off the power of your unit for several hours or overnight before draining it as the water will be unbearably hot and the tank will not cool off immediately. This ensures you can drain a hot water heater quickly and safely.

  • Cut off the cold water supply from your water heater.

Turn off the cold water supply valve to ensure that no more water can enter the tank when you start flushing the tank.

  • Connect the garden hose to the drain valve.

Once the tank is cooled down, attach the hose to the drain valve (near the bottom of the tank). Then, run the hose outdoors or into the bucket to dump the water later.

  • Open the hot water tap near the sink closest to your water heater to relieve the pressure of the entire system.

This step will help water flow smoothly and reduce the stress on the pipes, thereby, draining the tank faster. If you can’t find a nearby sink, any house water faucet (even if it’s farther) can work.

Stage 2: Drain The Unit

After the prep work, you may proceed with the actual draining procedure of your water heater.

  • Open the drain valve and empty the water tank.

You can turn the lever or knob to open the drain valve, but you can also use an adjustable wrench or a flathead screwdriver if you cannot open it by hand.

Once the valve is open, water will begin to spill out, so you have to make sure the hose is routed toward the floor drain. Alternatively, you can use a bucket and put the hose in it to catch the sediments efficiently.

However, this method requires you to pause and start the drainage process as you need to empty the bucket every time. Therefore, if your tank releases heavy sediment deposits, it will take you a while to drain your water heater. Repeat the process until no water is left to drain.

  • Flush the water heater tank with clean water.

Turn the cold water supply back on and let the incoming cold water rinse and remove the remaining sediment particles/residues at the bottom of the tank. Once the outpour is clear, turn the water valve off again. This step may take up to 5 minutes.

Stage 3: Getting Water Heater Ready For Use

For this stage, you need to check if the water heater is properly drained and ready for use.

  • Refill the water heater tank.

You may now shut off the drain valve and detach the garden hose. Make sure to remove any residual water inside the hose. After that, switch on the cold water shut-off valve and refill the tank.

Once the tank is full, turn the electric power on or relight the pilot light if you have a gas water heater. To avoid wasting water, turn off the sink faucet you opened earlier. Wait for an hour or so, and your water heater should serve you readily available hot water.

  • Check if the drain valve is closed properly.

Before leaving your water heater, inspect the drain spout and look for leaks. For any minor leaks, you can use a threaded hose cap to seal the end of the valve.

Tip: Avoid using plastic drain valves, and should you need to replace them, call a professional.

How Long Does It Take to Flush a Water Heater?

On average, it takes 10-20 minutes. Flushing is different from draining. It has the goal of replacing the water in the storage tank.

On the flip side, draining your water heater means emptying your tank. By doing this, you get the perks of knowing the condition of your domestic water. Water can go stale as time passes by. Hence, draining and flushing your water heater should be done periodically.


The primary reason to drain a water heater annually is to remove the sediment formation, dirt, and debris sitting at the bottom of your water heater tank. Draining your tank will prevent leaks and improve your household water quality.

You should now know how long does it take to drain a water heater, and I hope that you picked up applicable skills here, whether you need to flush or drain your water heater.

Do you have any problems with draining your tank? Do not hesitate to ask questions in the comment section below, and I will be more than glad to assist you!

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