Montreal Water-Cooled Air Conditioner Ban: Is Your AC Non-Compliant?

If you own a property in an older Montreal neighborhood—like the Plateau, Old Montreal, or the Sud-Ouest—you might be sitting on a “compliance time bomb.”

Since January 1, 2018, air conditioning units that use drinking water (aqueduct water) to cool the system without a recycling loop have been strictly prohibited under Montreal By-law 13-023. At Mose Home Inspection, our inspectors still encounter these “once-legal” units during building inspections. Whether you are buying a classic Montreal duplex or selling your condo, knowing the status of your water-cooled air conditioner in Montreal is critical to avoiding heavy fines and mandatory replacement costs.

Understanding Montreal By-law 13-023

The city’s stance is clear: any device used for cooling that consumes “potable water” (drinking water) and discards it directly into the drain without recycling it is illegal. This law was passed to modernize the city’s infrastructure and protect our most valuable resource.

Why Were Water-Cooled Air Conditioners Banned?

Standard water-cooled ACs are incredibly wasteful compared to modern air-cooled heat pumps or mini-split systems.

  • Massive Water Waste: A single residential water-cooled unit can consume up to 10,000 liters of drinking water per day. That is the equivalent of the daily water usage of 30 people.
  • Peak Demand Pressure: During heatwaves, the aqueduct system is under maximum stress. By banning these units, the city ensures there is enough water pressure for hydration, hygiene, and firefighting.
  • Environmental Impact: Treating and pumping water requires significant energy. Wasting treated drinking water to cool a machine is no longer ecologically or economically viable in a modern city.

How to Identify a Water-Cooled AC Unit

Many homeowners don’t even realize they have a banned system. Look for these three signs:

  1. No Outdoor Compressor: If you have central air but don’t have a large fan unit (compressor) on your balcony, backyard, or roof, your system is likely cooled by water.
  2. The “Hissing” Sound: When the AC is running, do you hear a constant sound of water flowing through the pipes and into a drain?
  3. Two Small Hoses: Check near your water main or under a sink. Illegal units are connected to a water intake pipe and a discharge pipe that leads straight to the sewer.

The Law: All units connected to the aqueduct without a recycling system must be retired. If you still have one, you are liable for fines ranging from $500 to $2,000 for individuals, and up to $4,000 for businesses.

2024/2025 Montreal Water Usage 
& Watering Rules

Managing the aqueduct load goes beyond AC units. Montreal has strict seasonal rules for watering and pool maintenance

Lawn Watering (Portable Sprinklers & Hoses)

Using a portable sprinkler or porous hose is only permitted between 8:00 PM and 11:00 PM on specific days:

  • Even-numbered addresses: Even-numbered dates.
  • Odd-numbered addresses: Odd-numbered dates.

Automatic Systems: Underground systems are generally restricted to 3:00 AM to 6:00 AM.

Filling Swimming Pools

  • Before May 15: You can fill your pool at any time.
  • After May 15: It is prohibited to fill a pool between 6:00 AM and 8:00 PM to ensure stable pressure for households during the day.

Protect Your Real Estate Investment

Buying a home with an illegal AC unit means you are inheriting a mandatory, high-cost renovation. During a Mose Home Inspection, we verify the cooling systems to ensure they comply with current Montreal by-laws. We document these findings in our comprehensive report.
If you suspect your unit is water-cooled, we recommend consulting a licensed HVAC technician to discuss a conversion to an air-cooled heat pump or a ductless mini-split system.

online today to ensure your property meets all Montreal environmental regulations.

Resources:

Frequently Asked Questions (FAQ)

A: It is not illegal to sell the house, but the unit itself is illegal to operate. You must disclose this to the buyer, as they will be responsible for replacing it. An inspection will flag this as a major non-compliance issue.

A: While technically possible, it is rarely cost-effective for residential properties. Most homeowners find that replacing the unit with a modern, energy-efficient air-cooled system is cheaper in the long run and qualifies for government rebates.

A: Yes. All commercial, industrial, and residential buildings must comply. Fines for businesses are significantly higher than for individuals.

A: Sometimes, when a water-cooled AC is removed or turned off, the P-trap in the drain line dries out. Refer to our guide on fixing sewer smells and dry P-traps for a quick fix.

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