Plumbing Advisors Editorial TeamEditorial StandardsUpdated June 8, 2026Source-CheckedWhy Descaling Matters
Scale is the same chalky mineral deposit you see around faucets, and inside a tankless heat exchanger it acts like an insulating crust that the unit has to fight through to warm your water. As it accumulates, the heater works harder, runs less efficiently, and can deliver a lower flow of hot water than it should. Descaling, also called flushing, circulates a descaling solution through the unit to dissolve that buildup and restore it to clean operation. How often it is needed depends largely on how hard your water is: homes with very hard water may need it once a year or more, while homes with soft water can go longer. Your unit's documentation and a professional can suggest the right interval for your area.
Simple Upkeep Between Descalings
Beyond periodic descaling, a few light tasks keep a tankless unit healthy, and several are safe for a homeowner to handle. The items below are the routine basics that help the unit run cleanly and let you catch small issues early.
- Clean the inlet filter screen: Many units have a small screen that catches debris before it enters the heater, and rinsing it periodically keeps water flowing freely.
- Keep the area clear: Make sure the space around the unit and any air intake or vent terminal stays free of clutter, dust, and obstructions.
- Watch for warning signs: Note any drop in hot water flow, fluctuating temperatures, or an error code on the display, which can signal scale or another issue.
- Check for leaks or corrosion: Glance at the connections now and then for any drips or staining, and call a professional if you find any.
- Track your descaling schedule: Note when the unit was last flushed so you stay on a sensible interval for your water hardness.
Hard water means more frequent descaling
If you have hard water, descaling is the single most valuable thing you can do for a tankless heater, and it may be needed yearly or more. A whole-home water softener can also slow scale buildup and reduce how often flushing is required. A professional can test your water and recommend a maintenance interval that fits your home.
What to Leave to a Professional
While cleaning the inlet screen and keeping the area clear are reasonable homeowner tasks, a full descaling flush involves the unit's gas or electrical supply and its water connections, and many homeowners prefer to have a professional handle it to be sure it is done safely and thoroughly. Anything beyond basic upkeep, such as a unit that is short on hot water, throwing error codes, leaking, or behaving erratically after a flush, calls for a pro rather than trial and error. Never open up the gas or electrical components of the unit yourself, and if you ever smell gas near a gas unit, leave the home and call your gas utility's emergency line from a safe distance.
When to Call a Professional
Routine descaling and any repair work are well suited to professional hands, since they touch the unit's connections and internal components. A tankless water heater installation service can perform or schedule descaling and check the unit over, and a water heater repair pro can diagnose a unit that is underperforming, leaking, or showing error codes despite regular care. If your unit was recently put in, our guide on what to expect during a tankless installation explains the setup that maintenance protects, and if you are still weighing the upkeep against the benefits, our guide on whether a tankless water heater is worth it puts the trade-offs in context.
Sources and further reading
These references support material safety, technical, consumer, or planning guidance in this article. Confirm property-specific requirements with the applicable authority and professional.
