A. O. Smith Tankless Water Heater Installation in Ontario
We install, replace and service A. O. Smith tankless water heaters across Southern Ontario, including the Adapt®+ with X3® Scale Prevention Technology. A. O. Smith designs the X3 so that regular descaling is not needed. On hard water, that removes the job that wears most tankless units out.
Tell us what you have now (a gas tank, a rental tank, or another brand of tankless unit that keeps needing descaling) and how many bathrooms run at once. We will tell you which A. O. Smith model fits and what the installation involves before anyone visits. Or send us the details.
Reviewed by the 1st Heat Home Comfort installation team · Updated 17 October 2026
What Hard Water Does to a Tankless Water Heater
Scale is the normal way a tankless water heater wears out in Southern Ontario. A tankless unit heats water as it flows through a narrow heat exchanger. Hard water carries dissolved calcium and magnesium, and heat makes them come out of the water and settle as limescale on exactly those surfaces.
The build-up does three things, slowly enough that most people live with it for a year before calling:
- It insulates the heat exchanger, so the burner works harder for the same hot water.
- It narrows the waterways, so flow drops and temperature starts to swing.
- It overheats the metal in the spots where it is thickest, which is how a heat exchanger eventually fails.
That is why most tankless water heaters need an annual descale: the unit is isolated, a descaling solution is pumped through the heat exchanger, and it is flushed and refilled. It works, but it is a visit every year for the life of the unit, and a skipped year shows up in the output.
What X3 Scale Prevention Changes
X3 is A. O. Smith’s answer to that yearly descale. According to A. O. Smith, it disrupts the normal process of scale formation and turns the minerals into smaller crystals that do not adhere to the heat exchanger surface, so they pass through with the water instead of building up.
| What A. O. Smith states | What it means in your home |
|---|---|
| Eliminates the need for regular descaling | No annual descaling visit. Routine servicing still applies, see below. |
| Extends the unit’s life up to three times vs. a tankless model without X3 | The failure that ends most tankless units early is the one X3 targets. Real life still depends on installation and water quality. |
| Maintained like-new efficiency and performance after 15 simulated years in A. O. Smith’s testing; models without X3 lost 10% in 1.5 simulated years | The burner keeps doing the same work for the same gas. These are the manufacturer’s own test results, not an independent study. |
| The 15-year limited warranty covers scale-related failures should they occur | Scale damage is a warranty matter on these models, rather than a maintenance failure you pay for. |
What X3 does not change. The Adapt+ is still a condensing gas water heater. The venting, the condensate drain and its neutraliser, the inlet water filter and the gas pressure all still need checking. Removing the descale takes away the biggest recurring job, not all of them.
Claims quoted from A. O. Smith Canada’s X3 Scale Prevention Technology and Adapt+ pages, read 17 October 2026. Warranty terms are the manufacturer’s and depend on the model, installation and use.
The A. O. Smith Adapt+ X3 Models We Install
The A. O. Smith Adapt®+ (often searched as AO Smith tankless) is a wall-mounted condensing unit sold in Canada in three sizes. All three carry X3 and an integrated recirculation pump.
| Model | Maximum input | Maximum flow | Efficiency | Venting and fuel |
|---|---|---|---|---|
| ATHR-160X3 | 160,000 BTU/h | 4.8 GPM | 0.95 UEF | 3-inch, natural gas or propane |
| ATHR-180X3 | 180,000 BTU/h | 5.3 GPM | 0.95 UEF | 3-inch, natural gas or propane |
| ATHR-199X3 | 199,000 BTU/h | 5.9 GPM | 0.95 UEF | 3-inch, natural gas or propane |
All three are ENERGY STAR certified and measure 27 by 17 by 16 inches. A. O. Smith Canada lists them as field convertible from natural gas to propane, with the kit included.
Read the flow column carefully. A. O. Smith rates the ATHR-199X3 at 5.9 GPM at a 67°F temperature rise, and an Ontario February asks for more than that: water coming in near 5°C has to be raised much further to make a comfortable shower. We size from your winter rise and the fixtures you actually run together. The full explanation, and how A. O. Smith compares with Navien, Rinnai and Noritz, is on our tankless water heater installation page.
Recirculation. The built-in pump can shorten the wait for hot water at a far bathroom. Whether you can use it depends on your plumbing: a home without a dedicated hot-water return line needs extra parts, and we include those in the quote rather than adding them afterwards.
Model figures from the ENERGY STAR certified gas water heater list (models ATHR-160X3, 180X3 and 199X3, Canadian market) and A. O. Smith Canada’s Adapt+ page, checked 17 October 2026. A. O. Smith also makes Adapt X3 models without the recirculation pump. Model availability changes, so we confirm the current figures for the unit we quote.
Replacing a Tank or Another Tankless Unit
Most A. O. Smith installs we quote are replacements. What changes depends on what is on the wall now.
From a gas or rental tank
A 40 or 50-gallon tank draws about 40,000 BTU/h; an Adapt+ fires at up to 199,000. The gas line often has to be resized or given its own run, and that is the most common added cost. The old flue is capped or abandoned properly, the new unit vents through sealed plastic pipe to a sidewall, and a condensate drain with a neutraliser goes in. If the tank is rented, the rental contract’s buyout or return terms belong in the comparison.
From a scaled-up Navien, Rinnai or Noritz
This is the swap X3 was made for. If your current tankless unit has needed a descale every year, has a scale warning showing, or has lost output on hard water, an X3 model removes that cycle. Much of the existing work can often be reused: the gas line was already sized for a tankless unit, and the venting route and condensate drain are already there. We check each one against the new unit’s requirements rather than assuming they carry over.
Not every scaled-up unit needs replacing. If yours is young and the heat exchanger is sound, a descale and a look at water treatment is the cheaper answer, and we will tell you so. See tankless water heater repair.
What Happens on Installation Day
- Site check confirmed. Gas line size and route, vent path to an exterior wall, condensate drain, power receptacle and water hardness, all measured before the day.
- The old unit comes out. Gas off, water drained, old tank or tankless unit disconnected and removed. A rented tank is set aside for the rental company.
- The Adapt+ is mounted on the wall, with isolation valves on the water lines so any future service is a short visit.
- Gas, venting and condensate. The gas line is connected or upgraded by a licensed gas fitter, the vent is run and sealed, and the condensate drain and neutraliser are fitted.
- Start-up and testing. Gas pressure checked under load, combustion verified, temperature set, and hot water run at the fixtures.
- Walk-through. We show you the controls, the filter, and what the warranty asks of you.
Gas work in Ontario is carried out by a licensed gas fitter under the rules of the Technical Standards and Safety Authority. Permit requirements depend on your municipality and the scope of the gas and venting work.
A. O. Smith Water Heater Repair and Service
We repair and service A. O. Smith tankless water heaters whoever installed them, along with Navien, Rinnai and Noritz units.
On an X3 model, scale is low on the list when something goes wrong, because that is the failure it is built to resist. That moves the usual suspects up:
- Gas supply and pressure, especially where another appliance was added to the line after the unit went in.
- Venting, including an intake or exhaust terminal blocked by snow or ice in winter.
- The condensate drain, which can freeze or clog and shut the unit down.
- The inlet water filter and the flow sensor, cheap parts that cause expensive-looking symptoms.
Routine servicing on an X3 covers exactly those checks, without the descale. For non-X3 units and the yearly descale, see water heater maintenance. For fault symptoms and error codes across all four brands, see tankless water heater repair.
X3 or a Water Softener?
They solve different problems, and on very hard water some homes want both.
| A. O. Smith X3 | Water softener | |
|---|---|---|
| What it protects | The water heater’s heat exchanger | The whole house: water heater, pipes, fixtures, dishwasher, washing machine |
| What it changes | Stops scale sticking inside the heater | Removes the hardness minerals from the water |
| Ongoing upkeep | Routine water heater servicing | Salt and periodic servicing |
| Good fit when | Your main concern is the water heater and its yearly descale | You also see scale on taps, glass shower doors and appliances |
If the spots on your shower glass bother you as much as the water heater does, a water softener is the broader fix. If the water heater is the concern, X3 deals with it at the source.
A. O. Smith Tankless Installation Across Southern Ontario
We install and service A. O. Smith tankless water heaters across Southern Ontario from our base in Concord. Water hardness and incoming water temperature both vary by area, which is why the model conversation starts with where you are.
Ajax · Barrie · Brampton · Brantford · East Gwillimbury · Guelph · Hamilton · Kawartha Lakes · Kingston · Kitchener · London · Markham · Mississauga · Niagara · Oakville · Orangeville · Oshawa · Ottawa · Peterborough · Richmond Hill · Smiths Falls · St. Catharines · Sudbury · Vaughan · Waterloo · Welland
If your town is not on the list, call (289) 409-9929 and we will tell you honestly whether we cover it.
A. O. Smith Tankless Water Heaters: Common Questions
Does an A. O. Smith X3 tankless water heater need descaling?
Not as regular maintenance. A. O. Smith states that X3 Scale Prevention Technology eliminates the need for regular descaling, because it changes scale into smaller crystals that do not stick to the heat exchanger. The unit still needs routine servicing: venting, condensate drain, inlet filter and gas checks.
Is the A. O. Smith X3 maintenance-free?
No. It removes the descaling step, which is the biggest maintenance job on a tankless unit in hard-water areas. The venting, the condensate drain and neutraliser, the inlet water filter and the gas supply still need checking, as on any condensing gas water heater.
What warranty comes with an A. O. Smith Adapt+ X3?
A. O. Smith Canada lists a 15-year limited heat-exchanger warranty and a 5-year limited parts warranty for residential use, and states that the 15-year limited warranty covers scale-related failures should they occur. Commercial use carries shorter terms. We give you the warranty terms in writing for the model we quote.
Is A. O. Smith or Rinnai better for a tankless water heater?
It depends on what you are solving. Rinnai SENSEI RX models publish a higher efficiency, 0.97 to 0.98 UEF against 0.95, but need an annual descale. The A. O. Smith Adapt+ X3 is designed not to need regular descaling, which matters most on hard water. We recommend on the house, not the badge.
Does X3 work on Ontario hard water?
That is what it is designed for. A. O. Smith recommends the X3 models for single-family homes with hard water concerns, and much of Southern Ontario is on hard water. It protects the water heater itself; it does not soften the water going to your taps, fixtures and appliances.
Do you service A. O. Smith tankless units another company installed?
Yes. We repair and service A. O. Smith, Navien, Rinnai and Noritz tankless water heaters across Southern Ontario, whoever installed them. Send us the model number from the label on the cabinet and any code on the display, and we can usually tell you what we are walking into.
How long does an A. O. Smith X3 tankless water heater last?
A. O. Smith states that X3 extends the unit’s life up to three times compared with a tankless model without it. Actual life depends on installation, water quality and servicing, which is why we look at all three before quoting.
Book an A. O. Smith Tankless Quote
Tell us what you have now, where it sits, and how many bathrooms run at once. We will tell you which Adapt+ X3 model fits and what the installation involves before anyone comes out.
Or send us the details and we will come back to you. Still comparing brands? See all four on our tankless water heater installation page, or all our water heater services.
