Where does a main drain sit in an Ottawa pool?

The main drain sits at the lowest point of the pool floor — typically centred at the deepest part of the pool, whether that is the deep end of a traditional hopper-bottom design or the centre of a flat-bottom pool. Its job is to pull water from the bottom of the pool into the circulation system, working alongside the skimmer to ensure the entire water column turns over properly.

In Ottawa pools, the positioning and construction of the main drain assembly is more critical than in warmer climates because of how deeply frost penetrates the ground here. Ottawa's frost line runs 1.2 to 1.5 metres deep, and the plumbing connecting your main drain to the equipment pad must be buried below that depth to avoid freeze damage. A drain line that runs too shallow through the pool floor or along the pool wall is vulnerable to frost heave — the ground literally shifts around it as water in the soil freezes and expands across Ottawa's 50-plus freeze-thaw cycles each winter.

Modern pools in Ottawa are required to have dual main drains separated by at least 900mm (roughly 3 feet) rather than a single central drain. This is a critical safety requirement under current standards — a single drain creates a powerful suction point that can trap a swimmer, particularly a child. Dual drains split the suction load and dramatically reduce entrapment risk. If you are looking at an older Ottawa pool with a single main drain, upgrading to a compliant dual-drain anti-entrapment cover assembly is a worthwhile safety renovation.

The drain covers themselves must be VGB-compliant anti-entrapment covers — flat or slightly domed covers with openings sized so they cannot create body or hair entrapment suction. These covers do wear and crack over time, and Ottawa's freeze-thaw cycles accelerate that wear. Inspect your drain covers every spring when you open the pool, and replace any cover that is cracked, missing, or loose. This is not a maintenance item to defer.

During winterization — which is absolutely non-negotiable in Ottawa's climate — the main drain line must be properly plugged at the pool end to prevent any water from sitting in the plumbing through the winter. Water left in the drain line will freeze, expand, and crack the pipe, potentially causing a repair that runs into the thousands of dollars come spring.