Descaling is a preventative maintenance process that removes calcium, magnesium, and other mineral deposits that accumulate inside your tankless water heater's heat exchanger coils—buildup that restricts water flow, reduces heating efficiency, and can lead to system failure if left unaddressed.
Over time, hard water minerals crystallize on the internal surfaces of your tankless unit's copper or stainless steel heat exchanger. This scale buildup acts as an insulator, forcing your heater to work harder to reach desired temperatures. The system compensates by increasing energy consumption, which drives up utility bills and accelerates wear on critical components like the ignition system and flow sensor. In severe cases, mineral deposits can completely block water passages, causing the unit to shut down or produce inconsistent water temperature—those frustrating temperature fluctuations that leave you with scalding water one moment and cold water the next.
The descaling process involves connecting a submersible pump to your tankless water heater and circulating a food-grade descaling solution (typically citric acid or proprietary formulations) through the heat exchanger for 45 minutes to several hours, depending on buildup severity. This chemical solution dissolves mineral deposits without damaging internal components. During the procedure, technicians monitor water clarity and pressure to confirm the system is clean. For tankless units installed in areas with water hardness above 7 grains per gallon, annual descaling is standard maintenance. Homeowners in moderate hard-water regions benefit from descaling every 18–24 months.
Why this matters: A properly descaled tankless water heater maintains peak efficiency, delivering consistent hot water on demand while minimizing energy waste. Clean heat exchanger coils allow your system to reach set temperatures faster, reducing strain on the heating element and extending the lifespan of expensive components. Descaling also restores water pressure—you'll notice improved flow at your showers and faucets. Most manufacturers, including Noritz and Rinnai units, recommend descaling as part of their warranty maintenance requirements; skipping this step can void coverage.
The cost of preventative descaling—typically $150–$300 per visit—is minimal compared to replacing a failed heat exchanger, which can exceed $1,200. Hard water also accelerates corrosion in your home's entire plumbing system, making descaling an investment in both your water heater and your pipes.
If you're experiencing reduced water pressure, temperature swings, or your tankless unit is making unusual noises, these are signs that descaling is overdue. Regular maintenance catches problems early and keeps your system running at peak performance.
Blackmon Plumbing, a licensed plumbing company (MPL-38162) with 19 years of experience and authorized service credentials for Noritz and Generac tankless systems, provides professional descaling and preventative maintenance to keep your water heater operating efficiently.