Tankless Water Heater Maintenance: Why Descaling Matters | KCs Plumbing

Jack Japuncic • June 6, 2026

Written by the team at KCs Plumbing, Heating & Drain Services · Reviewed by Jack Japuncic, Master Plumber

One of the appealing things about a tankless water heater is how little you have to think about it. No big tank in the corner, no obvious moving parts, just endless hot water when you want it. That low profile leads to a costly assumption: that no tank means nothing to maintain. There is something to maintain, and skipping it is the single most common reason a good unit starts underperforming or throwing errors it shouldn't.

What's Actually Happening Inside the Unit

Water passing through a tankless unit runs across a heat exchanger, and minerals in that water deposit onto its surfaces over time as scale, the same way a kettle scales up. There's also an inlet filter catching debris, and on gas models, a combustion system worth periodic inspection. Left alone, scale and a clogged filter quietly steal efficiency and flow, and eventually trigger the fault codes that bring people to a repair call that maintenance would have prevented.

Descaling: The One Thing That Actually Matters Most

Descaling, sometimes called flushing, circulates a cleaning solution through the unit to dissolve the mineral scale built up on the heat exchanger — the single most expensive component inside. Clear that buildup and you restore efficiency, protect that component, and keep hot water delivery steady. Skip it, and the unit works harder to deliver the same heat output, which shows up first as a slightly higher bill and eventually as reduced performance or an outright fault.

The Local Water Question People Actually Ask

Given how often we hear it: does this region's notably soft water mean tankless owners here can skip descaling? Not quite, but there's real truth behind the question. Lower mineral content in the water supply here does mean scale accumulates more slowly than it would in a hard-water city, which genuinely allows more breathing room on the descaling interval than manufacturer guidance written for the worst case assumes.

What it doesn't mean is zero maintenance. Scale still forms, just at a gentler pace. The inlet filter still needs clearing regardless of water chemistry. And gas units still need their combustion and venting checked on schedule. Soft water buys you a longer interval, not an exemption.

What a Full Service Visit Covers

Descaling the heat exchanger to clear mineral buildup and restore efficiency.
Cleaning or replacing the inlet water filter that protects the unit from debris.
Inspecting the burner, combustion, and venting on gas units for safe, clean operation.
Checking connections and error history to catch small issues before they become faults.

How Often, in Practice

An annual service is a sensible default, with this region's water chemistry giving some flexibility specifically on descaling frequency. Heavy-use households and commercial installations warrant tighter intervals. The simplest approach bundles descaling, the filter, and a combustion check into one yearly visit so nothing falls through the cracks, and if your unit has never been serviced at all, that first visit is the one that matters most.

Frequently Asked Questions

What Happens if I Never Descale My Tankless Unit?

Scale builds on the heat exchanger, reducing efficiency and flow, raising running costs, and eventually triggering faults or shortening the unit's life.

Can I Descale a Tankless Water Heater Myself?

Some homeowners do, but a professional visit also inspects the filter, combustion, venting, and error history — catching issues a flush alone would miss. Gas-related work should involve a licensed gas fitter.

Does Soft Local Water Mean I Can Skip Maintenance?

No; it means you can likely stretch the descaling interval, not skip maintenance altogether. The filter and combustion checks still matter regardless of water chemistry.

If your unit is currently acting up rather than just due for a checkup, faults often trace straight back to missed maintenance — our tankless repair guide covers that side of things. Otherwise, book a service visit at (604) 873-3753 or online and keep the unit performing the way it did on day one.