How To Clean and Maintain A Tankless Water Heater

Tankless water heaters can provide an efficient supply of hot water without the large storage tank used by traditional water heaters. However, like any plumbing appliance, a tankless water heater needs regular cleaning and maintenance to operate efficiently. Mineral deposits, especially from hard water, can accumulate inside the heat exchanger and reduce water flow, heating performance, and overall efficiency.

Learning how to clean and maintain a tankless water heater can help extend its service life and reduce the likelihood of performance problems. While some routine maintenance can be completed by a homeowner, more involved repairs and servicing should be handled by a qualified plumber.

Step 1: Turn Off The Water Heater

Before performing any maintenance, turn off the power or gas supply to the tankless water heater according to the manufacturer’s instructions.

If the unit operates on electricity, turn off the appropriate circuit breaker. For a gas-powered unit, follow the manufacturer’s directions for shutting down the appliance.

Allow the water heater to cool before beginning the cleaning process. Working with a recently operating water heater can expose you to very hot water.

Step 2: Shut Off The Water Supply

Locate the cold-water and hot-water isolation valves connected to the tankless water heater. Close both valves before disconnecting any plumbing connections.

If your unit has service valves specifically designed for flushing, make sure you understand how they operate before proceeding. These valves allow you to circulate a cleaning solution through the heat exchanger without flushing the entire home’s plumbing system.

Step 3: Connect The Flushing Hoses

Connect one hose to the service port on the cold-water side and another to the service port on the hot-water side. Connect the other end of the appropriate hose to the submersible pump.

Place the pump inside a five-gallon bucket and fill the bucket with the manufacturer’s recommended amount of descaling solution.

Make sure all connections are secure before opening the service valves. A loose connection could result in water or cleaning solution leaking onto the surrounding area.

Step 4: Flush The Heat Exchanger

Turn on the pump and allow the descaling solution to circulate through the tankless water heater. The solution helps dissolve calcium, lime, and other mineral deposits that can accumulate inside the heat exchanger.

Follow the water heater manufacturer’s instructions for the recommended flushing time. Depending on the equipment and level of buildup, the process may take an hour or longer.

Do not rush this step. Allowing the cleaning solution to circulate for the recommended amount of time gives it an opportunity to break down mineral deposits that could restrict water flow and reduce heating efficiency.

Step 5: Flush With Clean Water

After descaling is complete, turn off the pump and dispose of the used solution according to the product manufacturer’s instructions.

Flush the system with clean water to remove any remaining descaling solution and loosened mineral deposits. Again, follow the manufacturer’s directions for the appropriate flushing procedure and duration. Once the system has been thoroughly rinsed, close the service valves and disconnect the flushing hoses.

Step 6: Restore The Water Supply

Open the cold-water and hot-water isolation valves according to the manufacturer’s instructions. Check all connections carefully for leaks.

Once you are confident there are no leaks, restore power or gas service to the water heater. Follow the manufacturer’s startup procedure and verify that the unit is producing hot water normally.

Step 7: Clean The Exterior and Inspect The Unit

While performing routine maintenance, take a few minutes to inspect the outside of the water heater. Use a soft, dry or slightly damp cloth to remove dust and debris from the exterior.

Look for signs of corrosion, water leaks, damaged connections, unusual noises, or error codes on the control panel. Also inspect the surrounding area to make sure there is adequate clearance and ventilation as required by the manufacturer. Never remove gas components or attempt to repair electrical components unless you are qualified to do so.

How Often Should A Tankless Water Heater Be Cleaned?

The recommended maintenance schedule depends on the manufacturer’s specifications, your water quality, and how heavily the system is used. Homes with hard water may require more frequent descaling because minerals can accumulate inside the heat exchanger more quickly.

Regular professional inspections can also help identify developing problems before they lead to a loss of hot water or a more expensive repair.

Calling A Professional Is A Smart Move

Although flushing a tankless water heater may be possible as a DIY maintenance task, there are situations where professional service is the safer choice. Persistent error codes, leaking connections, unusual noises, inconsistent water temperatures, poor water pressure, and a lack of hot water can indicate problems that go beyond routine maintenance.

Gas-fired units require particular caution because improper work around gas lines, burners, or venting systems can create serious safety hazards. Electrical problems should also be addressed by a qualified professional.