Tankless Water Heater Annual Maintenance — Descaling and Care Guide
Published: July 15, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
Why Tankless Water Heaters Need Annual Maintenance
Unlike tank water heaters that can often go 2-3 years between maintenance, tankless units require annual descaling to maintain efficiency. Greater Vancouver water contains dissolved minerals that precipitate as scale inside the heat exchanger when water is heated. Over time, scale buildup reduces heat transfer efficiency, restricts water flow, and can cause the unit to overheat and shut down. A properly maintained tankless water heater achieves its rated efficiency and lasts 20+ years. A neglected unit may need premature replacement at 10-12 years.
The Descaling Process — What a Technician Does
Professional descaling involves connecting a pump and bucket to the isolation valves on your tankless unit. A food-grade descaling solution (typically white vinegar or a commercial descaler) is circulated through the heat exchanger for 45-60 minutes. This dissolves accumulated calcium and magnesium scale from the narrow passages inside the heat exchanger. After descaling, the system is flushed with fresh water to remove all residue. The inlet water filter is cleaned or replaced. The technician then checks combustion settings, verifies proper venting, and tests all safety controls.
Can I Descale My Tankless Water Heater Myself
DIY descaling is possible if your unit has factory-installed isolation valves with service ports. Without these valves, the descaling process requires disconnecting water lines, which risks leaks and water damage. The procedure requires a submersible pump, hoses, a 5-gallon bucket, and food-grade descaling solution. Most manufacturers recommend professional service to avoid damaging the heat exchanger or voiding the warranty. If you are comfortable with basic plumbing and your unit has service valves, a DIY descale takes about 2 hours. Professional service typically costs 150-250 dollars and takes about 1 hour.
Other Tankless Maintenance Tasks
Beyond descaling, inspect the vent termination outdoors to ensure it is clear of debris, nests, or snow. Clean the inlet water filter — a small mesh screen that prevents debris from entering the heat exchanger. Check the condensate drain on condensing units to ensure it flows freely. Verify the temperature setting on the controller — 120 degrees Fahrenheit (49 degrees Celsius) is recommended for normal household use. Test the pressure relief valve by lifting the lever briefly — water should discharge and the valve should reseat. If it does not reseat or continues to drip, replacement is needed.