Telltale signs: tankless water heater descaling
A tankless heater warms water as it passes through a compact heat exchanger. Minerals dissolved in the supply, chiefly calcium and magnesium, deposit on those hot surfaces over time. Because the channels are slim, even a modest layer reduces flow and makes the unit work harder.
The heater often tells you when it needs attention:
- Temperature swings in the middle of a shower
- Reduced hot water flow compared with the cold tap
- A scale or maintenance error code on the display
- Louder operation or the unit shutting down under demand
What we bring
- Drain hose, flux, torch and press tools
- Relief valve, dielectric unions, expansion tank
- Combustion and venting test gear
Tested before we leave
- Relief valve discharge pipe checked
- Gas or power connection leak-tested
- Hot water drawn at the furthest tap
On the job: what we open, clear and test
Most installations include isolation valves with service ports. We close the supply and outlet valves, hook a little circulating pump to the service ports with two hoses, and circulate a descaling solution through the heat exchanger for a set period. The solution is then drained, the unit is flushed with fresh water, and the inlet filter screen is removed and cleaned.
Before restoring power and gas, we check the valves for weeping and confirm that the condensate line, where fitted, drains freely. Finally, we run hot water at several fixtures and watch the unit's readings to confirm it is firing and modulating normally.
What can change the job
| Factor | Effect |
|---|---|
| Time since last flush | Heavy scale may need a longer cycle or a repeat. |
| Valve kit present | Without one, valves must be fitted first. |
| Water treatment | A softener slows buildup considerably. |
| Usage | Large households scale up faster. |
Etobicoke homes and this job
City water comes from the lake and is well treated, yet it carries a fair load of dissolved calcium, so tankless units across the west end benefit from regular flushing. Manufacturers generally publish a recommended interval; following it also helps keep warranty terms in order. Homes in areas like Smithfield that were updated with on-demand heaters during renovations sometimes have them mounted in tight spots, so we take care with hoses and drainage.
A descaling visit is also a good moment to look for small leaks around fittings, the kind that a leak detection check would otherwise uncover later. If a fitting has already let go, burst pipe repair covers that urgent situation. Buyers looking at a house with an existing unit may want to ask about its service history; our notes for buyers of older houses list further points to put to the seller.
Before you call
Note the brand and model number from the side label and any error code the screen shows. Find out, if you can, when the unit was last serviced. Make sure there is a floor drain or bucket space nearby, since we will be draining fluid during the flush.