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Tankless · Annual ServiceTankless Water Heater Maintenance Service
Tankless water heater maintenance service is an annual visit that descales the heat exchanger through the isolation valves, cleans the inlet water filter and air-intake screen, flushes the condensate trap, inspects the flame rod and igniter, and checks combustion. On Hamilton and Halton hard water the interval is once a year, and the annual descale flush runs $150–$300. Skip it and scale insulates the heat exchanger until the unit overheats, shows a code and shuts down.
Scale is the reason the service exists. A tankless unit heats water in narrow passages at high temperature, which is where dissolved calcium drops out, and a thin layer is enough to slow heat transfer and overheat the metal behind it. The descale closes the isolation valves, connects hoses to the service ports and circulates a descaling solution through the heat exchanger with a small pump for about 45 minutes to an hour, followed by a fresh-water flush. If your unit was installed without isolation valves, fitting a set is the first job and is quoted separately.
The rest of the list is short and specific. The cold-inlet filter screen catches grit and gets rinsed; the air-intake screen catches lint and dryer fluff that starve the burner. On condensing models the condensate trap is flushed, because a blocked trap backs acidic water into the unit. The flame rod and igniter are inspected and cleaned, and a combustion check confirms the burner is running clean at low fire and high fire.
Water hardness sets the interval. Municipal water across Halton and Hamilton is hard, so yearly is the working rule here; a rural well around Caledon, Kilbride or Flamborough with hard or gritty water may need it sooner. The unit also tells you when it is overdue: Rinnai displays LC codes for scale build-up, Navien logs E016 for an overheating heat exchanger, and ignition or flame-loss codes often trace to a dirty flame rod. Codes vary by model, so the manual for your unit wins.
Keep the paperwork. Manufacturers warrant residential heat exchangers for many years but exclude damage from scale and expect maintenance as the manual describes, so a dated invoice listing the work is what supports a claim. Each visit ends with a written record of what was done, the combustion readings and anything that is wearing. This page is the scheduled service; a unit that is already faulting belongs with tankless water heater repair, and the do-it-yourself steps are in our tankless maintenance guide.
Signs the annual service is overdue
- A scale or maintenance code on the display
- Water temperature that swings during a shower or sags when a second tap opens
- A rumble or crackle like a kettle while the burner is firing
- Weak flow at the hot taps only, the mark of a clogged inlet filter
- More than 12 months since the last flush, or no record of one (how to tell a tankless needs descaling)
How it works
Tell us the brand and model, whether the house has a softener, when it was last flushed and whether there are service valves under the unit. That decides how much descaler and time to bring. Book the service here.
Gas and power are shut off, the heat exchanger is descaled and flushed, the water filter, air screen and condensate trap are cleaned, and the flame rod and igniter are checked. Plan on roughly an hour and a half without hot water.
The unit is relit and combustion is checked with an analyzer. You get a dated record with the readings and the next due date, to file with the warranty registration.
Brands: We maintain Navien, Rinnai and Bosch tankless water heaters.
Common questions
How often does a tankless water heater need servicing around Burlington and Hamilton?
Once a year on unsoftened municipal water in Halton and Hamilton, which is hard. With a working softener, the first service shows how little scale comes out, and the descale can then move to a longer interval while the filters, condensate trap and combustion check stay yearly. Heavy use, a recirculation pump or well water shorten it: see hard water and tankless heaters in Hamilton and Halton.
What does tankless water heater maintenance cost?
The annual descale flush is $150–$300 for a residential unit. If the heater is already showing a fault, the visit starts as a $90–$150 diagnostic instead. A unit with no isolation valves needs a valve kit fitted first, which is quoted separately. There is more detail in tankless water heater maintenance cost.
Does skipping maintenance void the heat exchanger warranty?
It can cost you the claim. Heat-exchanger warranties exclude scale damage, and a manufacturer can ask for proof that the unit was maintained as its manual requires. Keep the installation invoice, the registration confirmation and a dated record of every service. Exact terms differ by brand and model, so check the warranty card that came with your unit.
Can I descale a tankless water heater myself?
Yes, if the unit has isolation valves and you are comfortable shutting off its gas and power. What a homeowner flush leaves out is the combustion check, the flame rod and igniter inspection and the condensate trap on a condensing unit, and those are what catch a burner problem early. On very hard water, a reasonable split is your own flush between professional visits.
My tankless shows a scale code. Is that a service or a repair?
If it still makes hot water, book the maintenance service: a scale code is a reminder, and the descale normally clears it. If the unit locks out, shows an ignition or flame-loss code that returns after a reset, or shuts off mid-shower, treat it as a fault call so the cause is diagnosed first.