Hard Water in Canadian Cities: What It Does to Boilers, Chillers and Cooling Towers, and When Commercial Pre-Treatment Pays Off
Quick answer: Canadian city water runs from very soft (Victoria, about 17 mg/L) to very hard (parts of Calgary, over 270 mg/L). Hard water can cause scale buildup on heat-transfer surfaces in boilers and cooling systems, reducing efficiency and increasing operating costs.
Hardness is the amount of dissolved calcium and magnesium in water, reported in milligrams per litre as calcium carbonate (mg/L as CaCO3). Municipal treatment plants make water safe to drink, but water that meets every drinking water guideline is not necessarily suitable for heating and cooling systems, where dissolved hardness minerals can form scale on heat-transfer surfaces.
This article gives the published hardness for each city Pace serves, explains how hardness affects heating and cooling equipment, and discusses when commercial water pretreatment, such as softening or reverse osmosis, may be beneficial.
How hard is the water in Canadian cities?
The figures below come from each utility’s most recent public water quality report. The classification follows the ranges Health Canada cites in its operational guidance: soft below 60 mg/L, moderately hard from 60 to 120, hard from 120 to 180, and very hard above 180.
| City | Water source | Hardness (mg/L as CaCO3) | Classification |
|---|---|---|---|
| Vancouver | Capilano, Seymour and Coquitlam reservoirs | About 20 (treated, 2025) | Soft |
| Victoria | Sooke Lake Reservoir | 17 (median) | Soft |
| Calgary | Bow River (Bearspaw plant) and Elbow River (Glenmore plant) | 141 to 274 (2025, varies by plant and season) | Hard to very hard |
| Edmonton | North Saskatchewan River | About 175 (2025) | Hard |
| Regina | Buffalo Pound Lake | 208 (2024) | Very hard |
| Saskatoon | South Saskatchewan River | About 160 (after lime softening at the plant) | Hard |
| Winnipeg | Shoal Lake | About 80 (2024 average) | Moderately hard |
| Toronto | Lake Ontario | 119 (2025 average) | Moderately hard |
| Montreal | St. Lawrence River | About 116 (Atwater and Charles-J.-Des Baillets plants) | Moderately hard |
Sources: Metro Vancouver 2025 Water Quality Annual Report; Capital Regional District; City of Calgary 2025 water quality data; EPCOR Edmonton monthly report, January 2025; City of Regina 2024 Drinking Water Quality Report; City of Saskatoon; City of Winnipeg 2024 treated water results; City of Toronto 2025 Drinking Water Analysis Summary; Ville de Montréal.
Two cautions apply to any table like this. First, hardness can vary seasonally. Calgary’s Glenmore plant reported 208 to 274 mg/L in the first quarter of 2025 and 191 to 216 mg/L in the third, reflecting seasonal changes in source-water conditions. Second, a building fed by a private well, or by a smaller municipal system outside these cities, can be far harder. Some well water in Canada exceeds 700 mg/L. The only reliable number for a given building is a test of its own makeup water.
What does hard water do to a boiler, chiller or cooling tower?
Calcium carbonate becomes less soluble as water gets hotter. This is the opposite of many other minerals, and it means scale can readily form on heated surfaces, such as boiler tubes, heat exchanger plates and water heater elements. The effects of hardness vary depending on the equipment and operating conditions.
Steam boilers
A steam boiler generates steam and leaves most dissolved minerals behind. Every litre of makeup water introduces additional calcium and magnesium, which can concentrate or precipitate as scale and sludge. In Regina, untreated makeup water with a hardness of 208 mg/L as CaCO₃ would introduce a significant hardness load to the boiler. Scale on boiler tubes acts as an insulator, increasing fuel consumption to maintain steam output and potentially causing the metal beneath the deposits to overheat.
Cooling towers and chillers
A cooling tower cools water by evaporating part of it. Evaporation leaves dissolved minerals behind, increasing their concentration in the circulating water. This concentration effect is measured in cycles of concentration. At four cycles, Edmonton makeup water with a hardness of 175 mg/L could theoretically reach 700 mg/L in the tower, assuming no hardness precipitation. In water-cooled chiller systems, scale on condenser tubes reduces heat-transfer efficiency, increasing refrigerant condensing pressure and compressor energy consumption.
Closed-loop heating and chilled water systems
A closed loop recirculates water with little routine makeup and does not concentrate dissolved minerals through evaporation as a cooling tower does. Scale potential depends on the fill water quality, operating temperature and system conditions, while corrosion is often the greater concern. Frequent top ups indicate water loss that should be investigated. Replacement water introduces dissolved oxygen and dilutes the corrosion inhibitor, increasing the need for monitoring and treatment adjustment.
Soft water has its own problem
Vancouver and Victoria water contains very little calcium or magnesium, resulting in low scaling potential. However, corrosion potential depends on several water chemistry factors, including pH and alkalinity, rather than hardness alone. Metro Vancouver adjusts pH and alkalinity at its treatment plants to help reduce corrosion.
What water hardness level causes scale in commercial boilers and cooling towers?
No single hardness number marks the point where scale starts. Whether water scales depends on its hardness, alkalinity, pH and temperature together, and on how many times the system concentrates it. When developing a treatment program, saturation indices, such as the Langelier and Ryznar indices, can help assess calcium carbonate scaling potential based on water chemistry and temperature.
For practical purposes, the answer differs by equipment:
- Steam boilers: makeup water generally requires softening or other appropriate pretreatment to achieve the low hardness levels specified for the boiler. Even Toronto and Montreal water, at approximately 120 mg/L, can cause significant scaling if fed untreated into a steam boiler.
- Cooling towers: the treatment program establishes appropriate operating cycles based on makeup water quality and system conditions. Higher hardness can limit achievable cycles of concentration, potentially increasing blowdown and treatment requirements. For example, a cooling tower using Calgary makeup water may be limited to three cycles of concentration, whereas a cooling tower using Vancouver makeup water with the same treatment program may be able to operate at eight or more cycles.
- Domestic hot water heaters: Domestic hot water heaters: scale builds on elements and in tanks in hard-water cities, and faster at higher storage temperatures. Treatment options include softening and the use of scale control products approved for potable water use such as Parafos®, which helps prevent scale formation through sequestration. .
How much energy does scale cost in a boiler or chiller?
The U.S. Department of Energy’s Steam Tip Sheet #7 estimates that scale deposits can increase fuel consumption in fire-tube boilers by up to 5%. Its table shows that scale of ordinary composition, 1/32 of an inch thick, can cause approximately 2% fuel loss, with thicker or iron-rich deposits potentially causing greater losses. Its table shows scale of ordinary composition, 1/32 of an inch thick, causing about a 2% fuel loss, and thicker or iron-rich scale causing more. For a boiler plant that burns $150,000 of natural gas a year, 2% is $3,000 and 5% is $7,500, every year the scale stays in place.
Chiller losses follow the same principle. Scale on condenser tubes reduces heat-transfer efficiency, increasing refrigerant condensing temperature and pressure, which in turn increases the compressor’s energy consumption. The size of the loss depends on the chiller, its load and the scale. Our article on how water treatment reduces energy costs covers the energy side in more detail.
Does a commercial building need a water softener or reverse osmosis?
It depends on which systems the water feeds and how much of it they use. Each pre-treatment technology removes something different:
| Equipment | What it removes | Typical commercial use |
|---|---|---|
| Ion exchange water softener | Calcium and magnesium, exchanged for sodium. Does not reduce total dissolved solids or alkalinity. | Steam boiler makeup, cooling tower makeup using a controlled blend of softened and unsoftened water where hardness warrants it, humidifiers and commercial kitchens |
| Reverse osmosis (RO) | Most dissolved solids, including hardness, alkalinity, silica and sodium | High-makeup steam plants, process water, humidification, laboratories |
| Multimedia or sand filtration | Suspended solids and turbidity | Cooling tower side-stream filtration, ahead of softeners and RO |
| Activated carbon filtration | Free chlorine, certain organic compounds, and chloramines when appropriately designed and sized | Ahead of RO, to protect the membranes |
Softening is a common pretreatment method for commercial steam boilers and is often sufficient for plants with good condensate return, when combined with an appropriate chemical treatment program. RO becomes beneficial when softened makeup water still contains excessive dissolved solids or alkalinity. In steam boilers, bicarbonate and carbonate alkalinity break down to form carbon dioxide, which leaves the boiler with the steam and forms corrosive carbonic acid in the condensate. RO removes most of the alkalinity from makeup water, reducing this source of condensate corrosion. In a cooling tower, silica or total dissolved solids can cap cycles even when hardness is managed. Depending on feedwater quality and system design, RO systems may require pretreatment such as softening or antiscalant dosing to prevent membrane scaling. Membrane cleaning may also be needed to maintain operating performance.
Existing softeners deserve attention too. Resin wears out, and many older units were sized for loads that no longer exist. Our article on raising the efficiency of commercial water softeners walks through a resin and vessel replacement that cut salt and water use.
When does commercial pre-treatment pay off?
Pre-treatment is often most cost-effective where makeup water consumption is high or water quality limits system efficiency. Four key factors influence the decision:
- Makeup volume. Steam plants with low condensate return require more makeup water than those with high condensate return. Large cooling towers can also consume significant volumes of makeup water due to evaporation and blowdown.
- Hardness and alkalinity. Regina and Calgary water can have approximately twice the hardness of Toronto water.
- Water, sewer and fuel rates. Blowdown carries both water and sewer costs, where applicable. In a steam boiler, it also discharges very hot water, losing heat supplied by the fuel unless that heat is recovered.
- Equipment value and downtime. Repairing or replacing scale-damaged equipment, such as boiler tubes or chiller condensers, can be considerably more expensive than appropriate pre-treatment, particularly when downtime costs are included.
Cooling tower blowdown shows how the numbers work. Assuming negligible drift and other water losses, makeup water equals evaporation multiplied by C ÷ (C − 1), where C is the cycles of concentration. A tower that evaporates 10,000 m³ per season requires 15,000 m³ of makeup at three cycles and 12,500 m³ at five cycles. Blowdown falls from 5,000 m³ to 2,500 m³—a 50% reduction in blowdown and a 2,500 m³ reduction in tower makeup.
Where hardness is the limiting factor, blending softened and unsoftened makeup water may allow higher cycles. RO may also support higher cycles by reducing dissolved minerals. The achievable target requires a full water analysis and review of operating conditions, including silica, alkalinity, corrosion and treatment limits. Financial savings depend on local water and sewer billing and any reduction in chemical losses. Net site water savings must also account for softener regeneration water or RO reject water.
What changes from one region to the next?
- Prairies (Calgary, Edmonton, Regina, Saskatoon): The hardest municipal water Pace serves. Softening is standard for most steam boilers, while cooling tower cycles may be limited by the higher hardness levels. Long heating seasons also increase the operating demands on building heating systems.
- Ontario and Quebec (Toronto, Montreal): Moderately hard municipal water. Steam boilers generally require softened makeup water, while cooling tower operating cycles depend on the overall makeup water chemistry and treatment program.
- Manitoba (Winnipeg): Moderately hard municipal water at approximately 80 mg/L, presenting a lower hardness load than many Prairie cities. Steam boilers still require appropriate makeup water treatment, oxygen control and corrosion protection.
- West Coast (Vancouver, Victoria): Very soft municipal water with low calcium carbonate scaling potential. Corrosion control may be a greater priority, while achievable cooling tower cycles depend on the overall water chemistry and treatment program.
Frequently Asked Questions
What is pre-treatment in commercial water treatment?
Pre-treatment is any process that conditions water before it enters a boiler, cooling tower or process. It includes filtration to remove suspended solids, softening to remove hardness, carbon filtration to remove chlorine, and reverse osmosis to remove most dissolved solids. Pre-treatment reduces the load on the chemical treatment program inside the system.
Is Calgary’s water harder than Edmonton’s?
Usually, yes. In 2025 the City of Calgary reported hardness of 141 to 274 mg/L as CaCO3, depending on the treatment plant and season, with the Elbow River supply to south Calgary at the higher end. EPCOR reported Edmonton total hardness of about 175 mg/L in January 2025. Both cities are classed as hard.
Does a closed-loop heating system need softened water?
Usually not. A closed loop is filled once, so the scale it can form is limited to the minerals in the fill water. Some facilities fill new loops with softened water as a precaution. A loop that needs regular top-up water has a leak that should be found, because each top-up adds hardness and oxygen.
Does soft water mean a building does not need water treatment?
No. Soft water has a lower potential for calcium carbonate scale formation, but it does not eliminate other water treatment concerns. Heating and cooling systems may still require corrosion inhibitors, biocides, and other treatment measures to control corrosion, microbiological growth and fouling. Treatment requirements depend on the water chemistry, equipment and operating conditions.
How do I find the hardness of my building’s water?
Your municipal utility publishes an annual water quality report with hardness figures. Hardness can change by season and by treatment plant, so the most reliable figure comes from testing the makeup water at your building. Pace can test your makeup water as part of a program assessment.
Pace’s regional teams test makeup water and design pre-treatment for local conditions, from softeners and RO to filtration. Learn more about our pre-treatment programs or contact your regional Pace representative to book a makeup water analysis.
