How to Flush a Tankless Water Heater

Regular maintenance is important to keeping your tankless water heater running efficiently and to extending its lifespan. With daily usage, it is common for tankless water heaters to have a layer of mineral build up, also known as scaling. This scaling needs to be flushed intermittently. In this guide, we will cover everything you need to know about flushing a tankless water heater.

In tankless water heaters, water passes through a heat exchanger and deliver continuous supply of hot water, over time, minerals like calcium and magnesium found in hard water accumulate on the heat exchanger, reducing its heating capacity and increasing the energy usage.

Regularly descaling a tankless water heater ensures the system operates efficiently and prevents costly repairs or even early replacement.

Improves efficiency: Flushing removes mineral deposits that restrict water flow and reduce heating efficiency.
Extends lifespan: A well-maintained heater will last longer without any hiccups.
Reduces energy costs: Scaling cause higher consumption of energy, thus increasing the energy bills.
Prevents clogs: Mineral buildup can cause blockages and hamper the flow of water

How frequently you should flush your tankless water heater depends on your water quality. If you live in an area with hard water (which is water high in mineral content), it is recommended that you flush your system at least once a year. If your water is soft, you may only need to flush the heater every two years.

That said, the general guideline is:

Hard water areas: Flush every 6 to 12 months.
Soft water areas: Flush every 12 to 24 months.
For high-usage households or homes using well water, more frequent flushing may be necessary.

The cost of flushing a tankless water heater varies depending on whether you DIY or hire a professional. A professional service typically costs between $150 and $250, including labor and materials such as a descaler. If you do it yourself, the cost lies between $100 to $400, depending upon the quality of the flush kit that you buy. Flushing on a regular basis, usually every 12 to 18 months, helps to maintain efficiency, reduce scale building, and extends the life of the heater. Regular maintenance can save you money on future repairs or replacements, ensuring that your water heater functions smoothly for many years.

Here’s a simple guide on how to flush and descale a tankless water heater

• Tankless water heater flush kit (which includes a submersible pump and hoses
• A bucket
• White vinegar (four gallons)

Before you start flushing your tankless water heater, turn off the power to the heater by unplugging it or switching off the circuit breaker. Next, close the hot and cold-water shutoff valves to stop water from flowing into the unit during the flushing process.

Attach the hoses from your tankless water heater flush kit to the hot and cold isolation valves. These valves are located on the pipes that bring water to and from your heater. The hoses will carry the vinegar solution through the unit to descale it.

Place the submersible pump from the flush kit into the bucket. Fill the bucket with approximately four gallons of white vinegar. Vinegar is a natural cleaning agent that breaks down mineral deposits without causing harm to your water heater.

Open the isolation valves and turn on the pump. The pump will circulate the vinegar solution through the heater. Let the solution run through the system for approximately 45 minutes. This process will dissolve and remove the calcium and magnesium deposits.

After descaling, turn off the pump and close the isolation valves. Drain the vinegar solution and refill the bucket with clean water. Run clean water through the heater by opening the isolation valves again for about 5 minutes to flush out any remaining vinegar and loosen mineral deposits.

Once the flushing process is complete, close the isolation valves, disconnect the hoses, and open the water supply valves to restore water flow. Finally, turn the power back on to your tankless water heater.

Run hot water from a faucet to ensure your tankless water heater is operating normally. If you’ve flushed it properly, your heater should now run more efficiently and provide consistent hot water.

In addition to regular flushing, follow these maintenance tips to keep your tankless water heater in top condition:

Clean the air intake filter: Make sure to check and clean the air intake filter every few months to prevent dust buildup that could affect the performance of your heater.
Check the pressure relief valve: Periodically check the pressure relief valve to ensure it’s working correctly.
Inspect for leaks: Look for any signs of water leakage around the unit and pipes, which could indicate a problem.

You should flush your tankless water heater at least once a year if you have hard water, or every two years in soft water areas. High-usage households may require more frequent maintenance.

Yes, with the right tools and a tankless water heater flush kit, you can flush and descale your heater yourself by following the steps outlined in this guide. However, if you’re uncomfortable with DIY maintenance, it’s best to hire a professional.

Failure to descale a tankless water heater can result in decreased efficiency, increased energy costs, and damage to the heat exchanger, which could lead to costly repairs or replacement.

Yes, white vinegar is an effective and safe descaling agent that can be used to remove mineral buildup in your tankless water heater.

Maintaining your tankless water heater through regular flushing and descaling is essential for optimal performance and longevity. By following the step-by-step guide and paying attention to how often to flush your system, you can ensure your water heater remains in great shape, providing endless hot water while saving energy and money.