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Commercial · Commercial Water Heater MaintenanceCommercial Water Heater Maintenance & Descaling
Commercial water heater maintenance and descaling means one full service a year for a storage tank and at least one descale a year for a tankless unit, sooner where the water is hard or the heater runs all day. The settings matter as much as the cleaning: store hot water at 60 °C to control Legionella, and deliver it through a thermostatic mixing valve so nobody is scalded at the tap. ZK Mechanical services commercial tanks, tankless racks and recirculation loops from Burlington across Halton, Hamilton and Peel.
An annual tank service is five jobs, not a quick drain. We flush the tank and remove sediment through the drain or the cleanout port, inspect the anode rods or test the powered anode, operate the temperature and pressure relief valve to prove it opens and reseats, clean the burner and run a combustion analysis, and check the vent and any condensate drain. Sediment is the one that costs money quietly: a layer on the tank bottom insulates the water from the flame, so the burner runs longer and the bottom of the tank overheats. The rumbling a neglected tank makes is steam bubbling up through that layer.
Descaling frequency on tankless and cascade systems is set by water hardness and hours of use, not by the calendar alone. Burlington, Oakville, Mississauga, Hamilton and Toronto draw from Lake Ontario, which is moderately hard; Georgetown, Acton, parts of Milton and the Caledon villages are supplied from groundwater, which is harder, and rural properties on private wells can be harder again. A café on lake water may hold a yearly descale, while a busy kitchen on well-fed supply can need it more than once a year. The reliable trigger is the heater itself: outlet temperature that swings, flow that falls off, or scale codes on the controller.
Temperature settings are a health control. Legionella bacteria grow in lukewarm water, so the tank is held at 60 °C and a thermostatic mixing valve blends it down before it reaches hand sinks and showers. Turning the tank down to save gas or prevent scalds trades one risk for a worse one; the mixing valve is the scald protection. We check the valve's outlet temperature with a thermometer at the nearest tap, because these valves drift and stick as they scale.
Buildings with a hot water return loop have two more parts to check: the recirculation pump and the aquastat or timer that controls it. A dead pump shows up as long waits for hot water at the far end of the building and a loop that sits lukewarm, which is the temperature range the storage setting was meant to avoid. We confirm the pump runs, the check valve holds and the return line comes back hot. Salons, clinics, fitness clubs and multi-tenant buildings are where we find these loops most.
If the heater has already failed, go to commercial water heater repair and replacement. General tank and tankless work is on the water heater page, and building-wide service agreements sit under commercial HVAC. To book a service or add water heaters to an existing visit schedule, get in touch.
Equipment we install and service
Flush and sediment removal, anode inspection, burner and flue cleaning, combustion analysis and a draft or vent check. Commercial tanks often carry more than one anode and a cleanout port, and both get used on a proper service.
Each heat exchanger is isolated and circulated with descaling solution, the inlet water screen and condensate trap are cleaned, and combustion and flow readings are logged per unit. In a rack we also confirm the controller is rotating the lead unit so wear is shared.
The T&P relief valve is operated to prove it works, the thermostatic mixing valve is measured at a tap, and the expansion tank's air charge is checked. A relief valve that drips after testing is replaced, never capped.
Pump operation, aquastat or timer setting, check valve and return temperature. A loop pump is a small part compared with the complaints, wasted water and bacterial risk of a loop that has stopped moving.
What goes wrong in these buildings
- The tank rumbles and bangs every time the burner fires.
- Hot water takes minutes to reach the washrooms at the far end of the building.
- The tankless rack throws a scale code every few months and one unit seems to do all the work.
- Someone turned the tank down to stop a scald complaint and now I am told that is a Legionella risk.
- Our gas bill for hot water keeps climbing and our usage has not changed.
- Nobody can show me a record of when this heater was last serviced.
How it works
The first visit records make, model, age, input and settings for every heater, tests water hardness on site, and measures storage, mixed and return temperatures. That gives each heater a service interval based on its own water and workload.
Flush, anode, relief valve, burner, combustion, venting and condensate for tanks; descale, screens and readings for tankless. Work is booked outside your peak hot-water hours and the heater is back in service before we leave.
You get dated readings and a list of anything wearing out, such as an anode near its end or a mixing valve drifting. The next visit is set from what we found, and the log is yours to show an insurer, landlord or public health inspector.
Common questions
How often should a commercial water heater be serviced?
Once a year for a gas storage tank is the baseline. Tankless units need descaling at least yearly and more often on hard water or long daily run hours, and heavily used kitchen tanks benefit from a mid-year flush. After the first service we set the interval from what came out of the tank and the hardness reading, so it reflects your building and not a generic schedule.
Is descaling different from flushing?
Yes. Flushing drains loose sediment from the bottom of a storage tank using water pressure. Descaling circulates a mild acid solution through a tankless heat exchanger to dissolve mineral scale bonded to the metal, then rinses it clear. Tanks mostly collect loose sediment and tankless units collect bonded scale, so each heater type gets its own procedure.
Why store at 60 °C if that is hot enough to scald?
Because the two risks are handled in different places. Storage at 60 °C keeps Legionella from growing in the tank, and the thermostatic mixing valve after the tank blends the water down to a safe temperature for hand sinks and showers. Dish machines and laundry can be piped ahead of the valve to get full temperature. Lowering the tank setting removes one protection without properly fixing the other.
Can water heater maintenance be added to our HVAC service contract?
Yes, and it is the efficient way to do it, since the technician is already on site for the rooftop units. Water heaters, mixing valves and recirculation pumps go on the same equipment list with their own interval and checklist, and the readings appear in the same report. Tell us what heaters you have when the contract is quoted.
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One licensed team for installs, maintenance contracts and 2 AM calls.