Maintenance Tips to Keep Your Tankless Water Heater Running Efficiently

How a Tankless Water Heater Works and Why Maintenance Matters

Unlike a traditional tank unit that keeps water hot around the clock, a tankless water heater heats water on demand by passing it through a heat exchanger the moment you open a tap. The design is what makes them so energy-efficient. There's no standby heat loss, and the unit only works when you need it to.

The tradeoff is that the heat exchanger, burner components, and water inlet screen all take on the full demand every time hot water runs. Minerals, debris, and combustion residue can build up and reduce heat transfer efficiency. If the issue is left ignored, the buildup forces the unit to work harder to reach the same output temperature, which shortens its lifespan and raises your energy bill.

The good news is that routine maintenance isn't complicated. A few tasks each year can prevent the most common performance problems and protect the equipment investment you've already made.

The Impact Hard Water and Mineral Buildup Have on Tankless Systems

Hard water is the number one maintenance challenge for tankless water heaters across most of the country. When water with high calcium and magnesium content heats up rapidly inside the heat exchanger, those minerals precipitate out of solution and coat the interior walls. This is called scale, and it's a serious problem.

A thin layer of scale acts as insulation inside the heat exchanger. The burner has to fire longer and hotter to push water past that layer and reach your target temperature. A heavily scaled unit can lose 25 to 40 percent of its heating efficiency and may start throwing error codes related to overheating or insufficient flow.

If your home has hard water above 7 grains per gallon, consider installing a dedicated water softener or a phosphate-based scale inhibitor upstream of the unit. A plumber can test your water and recommend the right pre-treatment solution for your supply. Skipping that step means descaling the unit more frequently and accepting more wear on the heat exchanger.

How to Flush and Descale Your Tankless Water Heater Properly

Descaling is the most important annual maintenance task for a tankless system. The process involves circulating food-grade white vinegar or a commercial descaling solution through the heat exchanger to dissolve mineral deposits. When done correctly, it restores heat transfer efficiency and clears any buildup inside the cold and hot water isolation valves. Here's a basic overview of the process:

• Shut off the gas or power supply to the unit and close the cold water inlet and hot water outlet valves.
• Connect a submersible pump to the cold water service port and run a return line from the hot water service port back into a five-gallon bucket.
• Fill the bucket with undiluted white vinegar and circulate it through the heat exchanger for 45 to 60 minutes.
• Flush the system with clean water for 10 minutes before reopening the isolation valves and restoring power.

If your unit hasn't been descaled in two or more years, or if you notice reduced hot water output and longer wait times at the tap, schedule a professional descaling with a plumbing repair service rather than attempting it yourself. Some scale buildup requires stronger descaling agents, and a technician can inspect the heat exchanger for physical damage while they're in there.

Filter Cleaning and Inlet Screen Maintenance You Should Not Skip

Most tankless water heaters include a cold water inlet filter screen designed to catch sediment and debris before they enter the heat exchanger. This screen is small, easy to overlook, and directly responsible for protecting some of the most expensive components in the unit.

A clogged inlet screen restricts water flow into the unit. When the flow drops below the minimum activation threshold, the unit won't fire at all or will cycle on and off erratically. Cleaning this screen takes less than 15 minutes and should happen at least once a year, or more frequently if your supply water carries visible sediment.

To clean the screen, shut off the cold water supply, locate the inlet port on the bottom of the unit, unscrew the filter housing, and rinse the mesh screen under running water. Inspect it for tears or corrosion while it's out. If the screen is damaged, replace it before reinstalling. Some units also include a hot water outlet screen worth checking at the same time. When in doubt about what filters your specific model uses, check the manufacturer's documentation or ask a plumber during your next service visit.

Warning Signs That Your Tankless System Needs Professional Attention

Some maintenance tasks belong in the homeowner's hands. Others are clear indicators that a plumbing repair service needs to take a look before the problem gets worse. Watch for these specific warning signs:

• Error codes on the display panel. These codes map to specific component failures. Don't ignore them or reset the unit without identifying the cause.
• Fluctuating water temperature. If your hot water runs hot, then lukewarm, then hot again during a single shower, the flow sensor or temperature regulator may be failing.
• Water pooling around the unit or visible corrosion on connections. Any active leak around a gas appliance warrants an immediate call to a professional.
• Unusual sounds during operation. Banging, crackling, or hissing during a heating cycle can indicate scale buildup, a failing heat exchanger, or gas pressure issues.

Delayed service on any of these issues can turn a repair into a full tankless water heater installation. Catching component failures early is almost always less expensive than replacing the unit.

Do You Need Professional Maintenance or a Tankless Water Heater Installation?

If you're overdue for service, noticing any of the warning signs above, or want a professional evaluation of your current setup, Trust Rooter is ready to help. Our team offers everything from routine maintenance to plumbing repair services and full system replacements. We know tankless systems inside and out, and we'll give you a straight answer on what your unit needs. Contact us today to schedule an appointment.