What are the City of Ottawa rules for draining pool water into the storm sewer?

The City of Ottawa prohibits discharging chlorinated or chemically treated pool water directly into the storm sewer system, and violation of the Sewer Use Bylaw (Bylaw 2003-514) can result in fines starting at $500 for residential properties. Storm sewers in Ottawa drain untreated into the Ottawa River, Rideau River, and local creeks, so chlorinated water, salt-system brine, or water with elevated copper-based algaecide levels can harm aquatic ecosystems and trigger enforcement action from both the City and the Ministry of the Environment, Conservation and Parks.

The correct procedure for draining pool water in Ottawa depends on where you are sending it and what chemicals it contains. The City allows pool water to be discharged into the sanitary sewer system — the same system that carries household wastewater to the Robert O. Pickard Environmental Centre for treatment. To do this legally, you must route the discharge through an indoor drain (floor drain, laundry tub, or cleanout) that connects to the sanitary sewer, not through an outdoor storm drain, catch basin, or directly onto the street where it would flow into a storm grate. Many Ottawa pool owners in neighbourhoods like Kanata, Barrhaven, and Orleans have a convenient floor drain in their basement near where the pool equipment is located, making this straightforward.

If you want to drain pool water onto your lawn or garden instead, the City requires that you dechlorinate the water first. Free chlorine levels must be at or near zero parts per million before discharge onto any surface that drains toward a waterway, ditch, or storm inlet. Dechlorination can be accomplished by stopping all chlorine or salt-system operation and allowing the water to sit exposed to sunlight for 3 to 7 days — Ottawa's summer UV intensity is sufficient to break down free chlorine naturally. Alternatively, you can add sodium thiosulphate (available at pool supply stores for $10 to $20 per kilogram), which neutralizes chlorine within minutes. One kilogram treats roughly 40,000 to 50,000 litres of pool water with a chlorine residual of 3 ppm.

Salt-system pools present an additional challenge for Ottawa homeowners. A typical residential salt pool contains 3,000 to 4,000 ppm of dissolved sodium chloride — equivalent to dumping 80 to 160 kilograms of salt onto your lawn or into a waterway if the entire pool is drained at once. Salty discharge kills grass, damages soil structure, and is toxic to freshwater organisms in the Rideau River watershed. The City of Ottawa's Sewer Use Bylaw does not set a specific salt concentration limit for residential discharge, but the Ontario Water Resources Act prohibits any discharge that impairs water quality. The safest approach is to drain salt pools into the sanitary sewer through an indoor connection, or to dilute the discharge heavily if draining onto permeable ground — for example, draining slowly over several days while running a garden hose to irrigate the lawn simultaneously.

Backwash water from sand filters and DE (diatomaceous earth) filters also requires proper disposal. Sand filter backwash contains suspended pool contaminants and residual chlorine; DE filter backwash contains diatomaceous earth powder, which can smother aquatic organisms if it reaches a waterway. Both should be discharged to the sanitary sewer, not onto the ground or into a storm drain. Some Ottawa pool companies install a permanent backwash discharge line routed to a sanitary cleanout — a worthwhile $200 to $500 investment during pool installation that avoids the hassle of dragging a backwash hose indoors every time you service the filter.

The practical enforcement picture in Ottawa works like this. The City's Environmental Services branch responds to complaints and conducts inspections. If a neighbour reports chlorinated water flowing into a storm drain or creek, a bylaw officer can visit your property, test the water, and issue a fine. First offences for residential sewer-use violations typically draw fines of $500 to $1,000, but repeat violations or discharges that cause documented environmental damage can escalate to $5,000 or more under the Ontario Water Resources Act. The City also has the authority to issue cleanup orders requiring you to remediate affected areas at your own expense.

Best Practices for Ottawa Pool Owners

The simplest compliance strategy is to plan your drainage route during pool installation rather than improvising later. Ask your pool installer to run a dedicated discharge line from the equipment pad to the nearest sanitary sewer cleanout or indoor floor drain. This typically costs $300 to $600 during initial construction — a fraction of what it would cost to retrofit later when the equipment pad and landscaping are already in place. For spring openings and fall closings, Ottawa pool service companies routinely pump waste water into a sanitary connection using a submersible pump and discharge hose, charging $75 to $150 if it is included as part of the opening or closing service.

For partial water replacement — the most common scenario — the volume is small enough that lawn discharge is practical if you dechlorinate first. Lowering the water level by 15 to 30 centimetres for winterization or topping off after heavy backwashing involves only 2,000 to 5,000 litres, which your lawn can absorb without issue as long as the chlorine level is at or near zero and the salt content is within normal range (below 500 ppm for non-salt pools).

Planning a pool installation or dealing with drainage questions this season? Ottawa Pool Installation connects homeowners with local pool professionals who build compliant drainage systems from day one.