How Long Does It Take to Drain a Water Heater?

how long does it take to drain a water heater

Draining a water heater is an important maintenance task that helps extend the life of your unit. By flushing out sediment that builds up over time, draining keeps your water heater running efficiently and can prevent unexpected leaks or failures. But how long does the draining process actually take?

The amount of time it takes to drain a water heater can vary based on the size and type of unit, as well as the draining method used. On average, draining a standard 40-50 gallon residential tank water heater takes 30-45 minutes. Larger or commercial units may take 1-2 hours to fully drain.


Before draining, be sure to turn off the power to the water heater at the breaker box and turn off the water supply. Locate the drain valve at the bottom of the tank and place a hose on the valve that runs to a floor drain or outside area. Open nearby hot water faucets to allow air flow. Have a bucket ready to catch any initial water release when opening the drain.

Draining Process

When ready, attach the hose securely to the drain valve and open it slowly. Water will begin flowing out rapidly at first. Let the initial rush of water flow out, catching it in the bucket. Once the flow slows to a steady stream, you can begin timing the drain. Monitor the flow of water and watch for any signs of sediment discharge.

On a standard residential unit, it should take 15-20 minutes for the tank to fully drain. Larger tanks or those with heavy mineral deposits may take closer to 30-45 minutes to drain completely. Avoid leaving the tank fully empty for longer than 30 minutes.


For a more thorough flush, close the drain once the tank is empty. Disconnect the hose and open the hot water release valve to allow new water to flow back in. This will stir up sediment and push it out through the drain. Close the release valve once the tank is full again and reconnect the hose. Re-open the drain valve to flush out the tank a second time. Repeat as needed until the water runs clear.

how long does it take to drain the water heater

When Draining is Complete

Allow the tank to fill back up fully with the drain valve closed. Check for any drips or leaks around the valve. Once full, turn the water supply back on and turn on a hot water faucet to purge any air from the lines. Finally, turn the power back on to the water heater. It’s always a good idea to follow up your draining with an annual maintenance checkup by a professional.

Key Takeaways:

– Draining a 40-50 gallon residential tank water heater takes 30-45 minutes on average. Larger tanks may take 1-2 hours.
– Properly preparing by turning off power and water, attaching a hose, and opening faucets speeds up the process.
– Flushing the tank twice helps remove more sediment and extends the benefits of draining.
– Following safety precautions when powering back on and checking for leaks prevents issues.
– Annual draining and checkups keep your water heater running efficiently for years.

When To Drain Your Water Heater

Draining your water heater periodically helps remove built-up sediment and mineral deposits from the tank. This maintenance helps the unit run more efficiently and can extend its lifespan. But how often should you drain your water heater?

Manufacturer’s Recommendations

Most residential water heater manufacturer’s recommend draining your unit at least once per year. Some may specify draining every 6 months, depending on the water supply mineral content in your area. If you notice reduced efficiency, rumbling noises, unusual smells, or changes in your hot water, draining more frequently may be needed.

Water Conditions

Hard water areas with high mineral content require more frequent draining to keep sediment from building up. Annually is usually sufficient for soft water areas. In areas with very hard water, draining 2-3 times per year may be needed. Doing a visual inspection for sediment when draining can help determine if your draining schedule needs adjusting.

Tank Type

Tankless water heaters do not require draining as frequently as storage tank heaters, but still need occasional flushing, around every 3-5 years. Flush a tankless heater if you notice mineral buildup in fixtures or changes in performance. Storage tanks should be drained 1-2 times per year in hard water areas.

how long does it take to drain a hot water heater

Tank Material

Stainless steel tanks allow for less mineral buildup over time compared to porcelain lined steel tanks. Prolong drain intervals for stainless steel tanks based on water conditions and visual inspections when draining. Porcelain tanks show more sediment over time and need draining at least annually.

In hard water areas, sediment accumulation happens quicker, so drain storage tank water heaters at least annually or every 6 months. Do a visual inspection each time to determine if more frequent draining is needed. Follow manufacturer’s instructions for tankless water heaters. Proper draining keeps hot water flowing efficiently.

When NOT to Drain Your Water Heater

While periodic water heater draining provides important maintenance, there are a few scenarios when you should avoid draining your unit:

– If the water heater is still under warranty – Draining the tank could void the warranty, so refer to manufacturer instructions during this period.

– When element is burned out – Draining with a burned out element could allow air to get trapped in the tank. Replace element first before draining.

– If tank leaks when draining – Leaks mean there is underlying damage. Draining further could worsen damage. Call a professional instead.

– No access to drain valve – Drain valves are usually at the bottom of the unit. If no valve access, a professional will need to assist.

– Sediment appears cemented on – Heavy buildup that appears cemented on indicates draining is overdue. Have a professional flush the tank.

– After recent work done – If piping was disconnected, wait 24 hours before draining to avoid issues.

The exceptions above are signs more extensive maintenance is needed. Professionals have the tools and knowledge to handle tricky draining scenarios. Only drain within your skill level to avoid tank damage or leaks. If in doubt, call for assistance to ensure the job is done safely.

Proper maintenance is key to efficient hot water heating. Knowing when NOT to drain your water heater prevents costly repairs or replacements down the road.


Draining your water heater periodically is an essential maintenance task that extends the life of your hot water system. For most standard residential units, expect the draining process to take 30-45 minutes. Draining at least annually, or every 6 months in hard water areas, helps reduce sediment buildup that can cause inefficiency and wear. Pay attention to signs your draining schedule needs adjusting, like reduced hot water flow or rumbling noises from the tank. Following safety precautions and manufacturer instructions prevents issues when draining. With proper maintenance, your water heater can provide reliable hot water for many years to come.


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