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Discharge Lines

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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Discharge is where drain water leaves your system. It has to go somewhere approved, and never back at the foundation.

I am a:

Tap your level and the boxes below open to the advice for you. Remembered on this device.

What it isThe pipe and outlet that carry sump or foundation drain water away from the house.
Your jobGet the discharge point approved, run solid pipe to a steady fall, and protect the line from freezing.
The hard ruleNever discharge to the sanitary sewer, a neighbour, a sidewalk or back at your own foundation.
The checkWritten approval for the outlet, a continuous fall, a working check valve, and an outlet that stays clear in winter.

By the end you can

  • Name the places drain water may and may not go.
  • Lay a solid discharge line with a check valve and a union.
  • Protect the line and outlet from freezing.
  • Find out what your municipality requires before you dig.
Stop and read

A discharge line can need a deep trench. One Canadian city's specification asks for 1.8 m (5 ft 11 in) of cover over buried lines, which makes a trench deeper than 1.2 m (4 ft). Follow the Trench Safety page and your provincial OHS regulator, and call for utility locates before you dig. Do not discharge where ice can form on a walk or street.

The big idea

Discharge is where drain water leaves the property's system. It has to go to an approved place, it must not flood a neighbour, and it must not run back to the foundation. Rules vary between municipalities, so check the local bylaw before you dig.

Where the water may go

Part 9 (Section 9.14, as printed in the Vancouver Building Bylaw 2014): foundation drains discharge to a sewer, a drainage ditch or a dry well (9.14.5.1). Where gravity drainage is not practical, an automatic sump pump does the same (9.14.5.2). A dry well is allowed only where the groundwater is below its bottom, and it must be at least 5 m (16 ft 5 in) from the foundation (9.14.5.3).

Municipal rules sit on top of that. Two Canadian municipal documents I read are examples, not your rules:

  • City of Regina, Section 1350 (rev. Jan 2017): discharge to a splash pad on the surface, or to a standpipe connected to a storm service. Sanitary sewer discharge is not allowed. Surface discharge is at least 1 m (3 ft 3 in) from the building and 2 m (6 ft 7 in) from the property line, and drainage must not spill onto a sidewalk or street. External underground pipe has at least 1.8 m (5 ft 11 in) of cover. A check valve is required, with a shut-off valve downstream and a union at the pump connection.
  • Town of Cobourg, Ontario: discharge outside, away from the foundation, to a ditch where one is available or to the storm sewer. No discharge to a floor drain, a laundry tub, a neighbouring property, a sidewalk or a roadway. Protect the line from freezing. It cites the Ontario Building Code and its sewer use by-law.

The distance and depth figures above are Regina's, not national. Roof water should go to its own system, not into the foundation drain. Call your municipality before you finalize the route.

Materials

  • Rigid solid pipe rated for the use, to a standard your code and municipality accept. Not perforated pipe.
  • Flexible hose is a temporary or seasonal measure only, and freezes and sags.
  • Size the pipe for the pump's flow. Regina's spec asks for sizing to suit the pump design conditions, and a retailer's guide uses 1 1/2 in PVC unless the pump maker says otherwise.

Check valve and union

  • Install the check valve above the pump, with the arrow pointing in the direction of flow. Regina's spec adds a shut-off valve downstream and a union at the pump connection, for maintenance.
  • Use a serviceable valve, and test it.

Slope and routing

  • Run the line to fall continuously away from the house, with no dips where water can freeze or sit. I did not find a Canadian code slope, and Regina's spec gives none, so follow your drawings and the municipality.
  • Keep it away from window wells, walks and neighbours' land.
  • Do not connect the sump discharge back into the foundation drain, and keep the outlet far enough from the wall that the water cannot re-enter the drain.

Example. A lot has 3 m (9 ft 10 in) between the house wall and the property line. Under Regina's distances the surface outlet must be 1 m or more from the wall and 2 m or more from the line, which needs at least 3 m. So it would fit with no margin at all, and you would look for a storm connection or another route. The lot is made up.

Freeze protection

  • Bury the line below frost depth where you can. Regina asks for 1.8 m (5 ft 11 in) of cover, which is deeper than 1.2 m, so trench safety applies.
  • Make sure the outlet cannot ice over or clog. Regina requires a standpipe to have a splash pad as an alternate outlet in case it freezes.
  • Follow the pump maker's advice on a relief fitting where freezing is a risk.

Outlets

  • Use a splash pad or erosion protection.
  • Keep the outlet clear of soil, leaves and ice.
  • Inspect it every season.

Common mistakes

  • Discharging next to the foundation
  • No check valve
  • Hose used as a permanent line
  • Not enough fall
  • Frozen or blocked outlet
  • Discharging onto a neighbour, sidewalk or street
Pro note

Ask the municipality before you finalize the discharge. It is a quick call, and it avoids rework.

Weather note

Freezing can block or split the line, and heavy rain increases demand. In cold areas, plan the route and outlet for winter.

What the inspector looks at

Where the water goes, the routing and slope, the check valve, and freeze protection.

✅ Check yourselfTap a question
Under one city's specification, the line has 1.8 m (5 ft 11 in) of cover. Is the trench deeper than 1.2 m (4 ft)?
Yes. 1.8 m of cover plus the pipe and bedding is a trench well over 1.2 m (4 ft), so the trench safety rules apply to the digging. That city's figure is an example, so confirm yours.
A lot has the house wall 3 m (9 ft 10 in) from the property line. One city requires surface discharge at least 1 m (3 ft 3 in) from the building and 2 m (6 ft 7 in) from the property line. Is there room?
The outlet must be at least 1 m from the wall and at least 2 m from the line. With 3 m between them, the only spot that works is exactly 1 m from the wall, which is also exactly 2 m from the line. There is no margin, so look for a different outlet, such as a storm connection or a ditch.
May a sump discharge to a floor drain or the sanitary sewer?
No. Two Canadian municipal documents prohibit it. Foundation and sump water belongs in a storm sewer, ditch, dry well or surface outlet that the municipality allows.
Why a check valve and a union?
The check valve stops water in the line running back into the pit. The union lets you remove the pump. One city's spec requires both, with a shut-off valve downstream of the check valve.
What does Part 9 allow as a discharge for a foundation drain?
A sewer, a drainage ditch or a dry well (9.14.5.1). A dry well is allowed only where groundwater is below its bottom, at least 5 m (16 ft 5 in) from the foundation (9.14.5.3). Municipal bylaws may restrict these.
It is winter, and the outlet is a flexible hose lying on the ground. What goes wrong?
It freezes and blocks, the pump cycles against a full line, and water backs up. Use buried solid pipe, or follow the maker's and municipality's freeze advice.
🧰 Gear for this stepMust-haveRent itNice to have
  • Must-haveLayout and measuring (basics):
  • Nice to haveLayout and measuring (laser): a laser for long runs, to keep a steady fall
  • Must-havePipe:
  • Must-haveValve and fittings: a serviceable check valve, a union, and a freeze-relief fitting if the pump maker calls for one
  • Must-haveDigging and backfill:
  • Must-haveOutlet: a splash pad or erosion stone, and a screen or grate if the outlet needs one
  • Must-havePPE:
👷 Who can do thisTap your level
Home DIY
A capable owner can run a solid discharge pipe in a shallow trench, well under 1.2 m (4 ft) deep, once the municipality has said where the water may go. Some cities want a deeper line for frost cover, and a trench that deep is not a DIY entry. Never enter a deeper trench, and do not judge sloping or shoring yourself. Do not discharge onto a neighbour, a street or the foundation. Call the municipality first, and hire a plumber where a storm sewer connection or permit is needed.
Laborer or helper
Carry pipe, clean the trench edge and hold the line while the crew lays it. Never enter a trench unless a qualified person has made it safe. Tell the lead if the outlet looks blocked or water is heading toward a neighbour.
1st-year apprentice
Under supervision, lay pipe to a steady fall, glue joints and fit the check valve. Learn first why the outlet must stay clear and how freezing breaks lines.
Apprentice, 2nd to 4th year
Lay and glue pipe to the steady fall marked on the plan, and fit the check valve under direction. Stay out of any unprotected trench. Learn to spot a flat spot or low point where water and ice will sit.
Journeyperson
You own the routing, slope, outlet and freeze protection, and the discharge approval from the municipality or inspector. Stop-work triggers: the municipality has not approved the discharge point, or the route cannot hold a continuous fall away from the house.
Lead hand or foreman
Hold the stop-work triggers: no pipe goes in until the discharge point is approved. Check the fall to the outlet at every joint. Take any plumbing-permit question to the inspector or building department, not to a guess, and confirm trench rules with your OHS regulator.
Contractor or business owner
Price the route and the permit, and get the discharge approved in writing before you build. Document the route with photos and as-built notes. Water on a neighbour's land is a claim risk. Ask your lawyer or insurer who carries the liability.
Starting a new business
Get the discharge approval in writing from the municipality before you price or build. Ask your lawyer or insurer who is liable if water reaches a neighbour. Confirm plumbing permit rules with your building department, and subcontract a plumber for any storm sewer tie-in.
By Province:

This page is mostly local. Part 9 gives the broad rule, and the plumbing code and municipal bylaws decide where the water may go, at what distance, and at what depth. The two municipal documents I read (Regina and Cobourg) show how different the details can be. I did not check any other province, so confirm with your municipality and your provincial plumbing code.

See Canada by Province for the full comparison.

Sources:

Last reviewed October 2026. General information, not engineering or legal advice.

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