Where Fleet Wash Water Can Legally Go in Ontario

Washing a commercial fleet produces waste, not just water. Where that waste is allowed to go is set by municipal sewer-use by-laws, and it is the part of a fleet washing quote that almost never gets discussed until something has already gone down a drain.

This guide covers the mechanism, who carries the liability, the three setups that are normally acceptable, and the questions worth asking before a contractor turns a hose on in your yard. It is written for fleet managers, yard supervisors and property managers in the Greater Toronto Area.

The rule, in one sentence

A sanitary sewer goes to a treatment plant. A storm sewer goes to a creek, a river or the lake, with no treatment in between. Catch basins — the square grates in your lot and at the roadside — connect to the storm system.

The City of Toronto states it about as plainly as it can be put:

"Nothing other than rain and melted snow should ever enter a catch basin (square grates on the road). Catch basins are connected to storm sewers, which drain directly into rivers, streams and the Lake." — City of Toronto, Sewers By-law (Municipal Code, Chapter 681)

Fleet wash water is not rain. It carries diesel and engine oil residue, road salt, brake dust and metals, and whatever detergent or degreaser was used to lift them. Undercarriage and fifth-wheel work adds heavy grease on top. Sewer-use by-laws exist precisely to set limits on that kind of discharge.

Who administers it where you are

This trips people up, because the authority is not always the city whose name is on the sign. In two-tier parts of the GTA, sewer use is regulated at the Regional level.

Every entry above is taken from that authority's own published pages or by-law register, checked on 13 August 2026. By-laws are amended; confirm the current version with the Region rather than relying on a summary — including this one. By-laws are amended; check the consolidated version before relying on any figure or limit.

Who is actually liable

Both the contractor and the property owner or occupier can be exposed. Sewer-use by-laws regulate what is discharged into the sewer system from a property, which is why "the contractor did it" is not a reliable defence for a site owner. The practical consequence is that the person with the most to lose from an unlawful discharge is often not the person holding the pressure washer.

That is the whole reason to settle this before the first wash rather than after a complaint. It costs nothing to ask at the quoting stage and a great deal to resolve afterwards.

The three setups that normally work

1. The site already handles it

Many distribution facilities, transport terminals and older industrial yards have a designated wash pad draining to sanitary sewer, or an oil–water separator installed for exactly this purpose. If yours does, washing on site is straightforward. Worth confirming rather than assuming: separators need periodic servicing, and a neglected one is not doing the job it was installed to do.

2. Containment and recovery brought to site

Where a yard has no suitable drainage, wash water can be contained at the point of work — berms, mats or booms — and recovered by vacuum for disposal or treatment elsewhere. This is specialist equipment. A contractor arriving with a pressure washer and no recovery plan is not offering this option, whatever they say on the phone.

3. The work moves

Sometimes the sensible answer is to wash at a facility already built for it rather than construct a containment operation in a yard that will never need one again. For a small fleet, this is frequently the cheapest compliant route.

What to ask before anyone starts

1. Where will the wash water go on this site? A specific answer, not "it'll be fine."
2. If it goes to a drain, is that drain sanitary or storm — and how do you know? Site drawings, a dye test, or the property manager. Not a guess from looking at the grate.
3. If there is no suitable drainage, what containment and recovery are you bringing? Named equipment, and who disposes of the recovered water.
4. Who is named if there is a complaint? Establish this while everyone is still friendly.

This guide is part of our free cleaning reference library. If you also need to evidence trailer sanitation for a shipper or an audit, use the free trailer washout log.

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Frequently asked questions

Can I wash trucks in my own yard in Ontario?

Often yes, but it depends entirely on where the water ends up. If the yard drains to a sanitary sewer connection or a designated wash pad, washing there is normally straightforward. If the only drainage is a catch basin, that catch basin leads to a storm sewer and then to a creek or the lake without treatment, and discharging wash water into it is prohibited under municipal sewer-use by-laws. The surface you are standing on does not decide this. The drain does.

What is the difference between a storm sewer and a sanitary sewer?

A sanitary sewer carries wastewater to a treatment plant. A storm sewer carries rainwater and melted snow straight to a watercourse with no treatment at all. Catch basins - the square grates in a parking lot or at the roadside - are connected to storm sewers. The City of Toronto puts it plainly: nothing other than rain and melted snow should ever enter a catch basin.

Who is liable if wash water enters a storm drain?

Both the contractor doing the washing and the owner or occupier of the property can be exposed. Sewer-use by-laws regulate discharges into the sewer system from a property, so a defence of 'the contractor did it' does not necessarily move the liability off the site. This is the practical reason to settle the question before work starts rather than after an inspector arrives.

What is in fleet wash water that makes it a problem?

Road film from a commercial vehicle is not simply dirt. It carries diesel and engine oil residue, road salt, brake dust and metals, plus whatever detergent or degreaser was used to lift it. Undercarriage and fifth-wheel work adds heavy grease. That mixture is exactly what sewer-use by-laws set limits on, which is why untreated discharge to a storm sewer is treated differently from rinsing a car on a driveway.

What should I ask a fleet washing contractor before they start?

Four questions. Where will the wash water go on this site. If it is going to a drain, is that drain sanitary or storm, and how do they know. If the site has no suitable drainage, what containment and recovery are they bringing. And who is named on the paperwork if there is a complaint. A contractor who has not thought about any of this is a contractor whose work becomes your problem.

Does this apply outside Toronto?

Yes, though the authority changes. Toronto administers its own Sewers By-law. In the two-tier parts of the Greater Toronto Area the by-law usually sits with the Region rather than the local city - York Region's Sewer Use Bylaw, for example, applies to all people and businesses in York Region, which covers Markham, Vaughan, Richmond Hill, Newmarket and Aurora. Durham Region administers Sewer Use By-law 055-2013 across Oshawa, Whitby, Ajax and Pickering. Peel Region administers Wastewater By-law 53-2010 across Mississauga, Brampton and Caledon, and Halton Region's By-law 2-03 covers Oakville, Burlington and Milton - and Halton's explicitly names storm sewers as well as sanitary, which is the one that catches a wash bay draining to a catch basin.

References & further reading

• City of Toronto. Sewers By-law (Municipal Code, Chapter 681).
• York Region. Sewer Use Bylaw — regulates water and waste entering sanitary and storm sewer systems across the Region.
• Region of Durham. Sewer Use By-law 055-2013 — a by-law to define and govern the use of the Region's sewer works (adopted 30 October 2013).
• Region of Peel. Wastewater By-law 53-2010, amended by By-laws 48-2014 and 5-2024 — listed on the Region's by-law register.
• Region of Halton. By-law 2-03 — prohibits, regulates and controls discharges into bodies of water within regional boundaries or into Halton's regional sanitary sewers, storm sewers, sanitary sewage works and all tributary sewer systems.
• Ontario Ministry of the Environment, Conservation and Parks. Ontario Water Resources Act — provincial framework for discharges to water.

Note: general educational summary, not legal or regulatory advice. By-laws are amended, limits differ between municipalities, and the requirements that apply to your site depend on its drainage and your activity. Verify against the current by-law for your municipality or Region before relying on any of this.

Zusashi arranges commercial fleet washing across the GTA and settles the wash-water question at the assessment, before a quote is issued — because the answer changes what the job costs and, occasionally, where it can happen at all.