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Code guide

Sump Pump and Sump Pit Rules in Ontario

Sump pits and pumps in the 2024 Ontario Building Code: 750 mm deep, 0.25 m² pit, child-proof airtight cover, where foundation drains discharge, valves.
minimum sump pit depth
750 mm
minimum sump pit depth
minimum sump pit area
0.25 m²
minimum sump pit area
child-resistant cover
Airtight
child-resistant cover
dry well from the foundation
5 m
dry well from the foundation

Last updated

Under the 2024 Ontario Building Code, a sump pit must be at least 750 mm deep and at least 0.25 m² in area, with a cover that resists removal by children and is airtight (OBC Div. B 9.14.5.2.OBC Div. B 9.14.5.2. Sump Pits(1) Where a sump pit is provided it shall be (a) not less than 750 mm deep, (b) not less than 0.25 m² in area, and (c) provided with a cover. (2) Covers for sump pits shall be designed (a) to resist removal by children, and (b) to be airtight in accordance with Sentence 9.25.3.3.(7) (3) Where gravity drainage is not…). Where foundation drains cannot drain by gravity to a sewer, ditch or dry well, an automatic sump pump is required to lift the water out (9.14.5.1.OBC Div. B 9.14.5.1. Drainage Disposal(1) Foundation drains shall drain to a sewer, drainage ditch or dry well., 9.14.5.2.(3)OBC Div. B 9.14.5.2. Sump Pits(1) Where a sump pit is provided it shall be (a) not less than 750 mm deep, (b) not less than 0.25 m² in area, and (c) provided with a cover. (2) Covers for sump pits shall be designed (a) to resist removal by children, and (b) to be airtight in accordance with Sentence 9.25.3.3.(7) (3) Where gravity drainage is not…).

This page covers sump pits and pumps for houses and other Part 9 buildings, plus the plumbing rules for the discharge pipe. Where the water may go is also set by municipal sewer use by-laws, and your building department decides how the code applies.

Sump rules at a glance

Item Rule in short Where to look
Where foundation drains go sewer, drainage ditch or dry well 9.14.5.1.
Sump pit size at least 750 mm deep and 0.25 m² 9.14.5.2.(1)
Sump pit cover child-resistant and airtight 9.14.5.2.(2)
Sump pump automatic, where gravity drainage is not practical 9.14.5.2.(3)
Dry well groundwater below its bottom; 5 m from the foundation 9.14.5.3.
Subsoil water sump water- and airtight cover 7.4.6.3.(3)
Storm sump discharge union and check valve, or union, check and shut-off valve 7.4.6.3.(9)
Pumped sump discharge union, backwater valve and shut-off valve, in that order 7.4.6.3.(7)
Sewage sump water- and airtight, vented 7.4.6.3.(2)

This is our summary of the articles, not a copy of the code. Read the full text before you install a sump.

Where foundation drainage must go

Foundation drains, the weeping tile around the footings, must drain to a sewer, drainage ditch or dry well (9.14.5.1.OBC Div. B 9.14.5.1. Drainage Disposal(1) Foundation drains shall drain to a sewer, drainage ditch or dry well.). If the outlet is lower than the drains, water flows by gravity and no pump is needed. If it is not, the drains run to a sump pit, and an automatic sump pump must discharge the water to the sewer, ditch or dry well (9.14.5.2.(3)OBC Div. B 9.14.5.2. Sump Pits(1) Where a sump pit is provided it shall be (a) not less than 750 mm deep, (b) not less than 0.25 m² in area, and (c) provided with a cover. (2) Covers for sump pits shall be designed (a) to resist removal by children, and (b) to be airtight in accordance with Sentence 9.25.3.3.(7) (3) Where gravity drainage is not…).

A dry well can only be used where the natural groundwater level is below the bottom of the dry well, and it must be at least 5 m from the foundation and placed so drainage flows away from the building (9.14.5.3.OBC Div. B 9.14.5.3. Dry Wells(1) Dry wells may be used only when located in areas where the natural groundwater level is below the bottom of the dry well. (2) Dry wells shall be not less than 5 m from the building foundation and located so that drainage is away from the building.).

Many Ontario municipalities do not accept foundation drainage in the sanitary sewer, and some offer programs to disconnect it. Check your municipality's sewer use by-law before choosing the discharge point.

The sump pit

Where a sump pit is provided, it must be (9.14.5.2.(1)OBC Div. B 9.14.5.2. Sump Pits(1) Where a sump pit is provided it shall be (a) not less than 750 mm deep, (b) not less than 0.25 m² in area, and (c) provided with a cover. (2) Covers for sump pits shall be designed (a) to resist removal by children, and (b) to be airtight in accordance with Sentence 9.25.3.3.(7) (3) Where gravity drainage is not…):

  • at least 750 mm deep,
  • at least 0.25 m² in area, and
  • covered.

The cover must be designed to resist removal by children and to be airtight in line with the air barrier rules (9.14.5.2.(2)OBC Div. B 9.14.5.2. Sump Pits(1) Where a sump pit is provided it shall be (a) not less than 750 mm deep, (b) not less than 0.25 m² in area, and (c) provided with a cover. (2) Covers for sump pits shall be designed (a) to resist removal by children, and (b) to be airtight in accordance with Sentence 9.25.3.3.(7) (3) Where gravity drainage is not…). An open sump is a drowning risk for small children and a path for soil gas into the basement. See the radon guide for the soil gas rules.

The discharge pipe

The plumbing rules in Part 7 cover the pipe from the pump (7.4.6.3.OBC Div. B 7.4.6.3. Sumps or Tanks(1) Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank. (2) Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented. (3) Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall…):

  • A pumped storm sump discharge pipe needs a union and a check valve, in that order, pumped to above grade level, or a union, check valve and shut-off valve, in that order (7.4.6.3.(9)OBC Div. B 7.4.6.3. Sumps or Tanks(1) Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank. (2) Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented. (3) Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall…).
  • The discharge pipe from a pumped sump connected to the drainage system needs a union, a backwater valve and a shut-off valve, in that order in the direction of flow (7.4.6.3.(7)OBC Div. B 7.4.6.3. Sumps or Tanks(1) Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank. (2) Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented. (3) Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall…).
  • A sump receiving subsurface water from a subsoil drain needs a water- and airtight cover (7.4.6.3.(3)OBC Div. B 7.4.6.3. Sumps or Tanks(1) Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank. (2) Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented. (3) Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall…).
  • A sump receiving sanitary sewage (a sewage ejector pit) must be water- and airtight and vented (7.4.6.3.(2)OBC Div. B 7.4.6.3. Sumps or Tanks(1) Only piping that is too low to drain into a building sewer by gravity shall be drained to a sump or receiving tank. (2) Where the sump or tank receives sanitary sewage, it shall be water- and air-tight and shall be vented. (3) Where the sump or tank receives subsurface water from a subsoil drainage pipe, it shall…).

Where a subsoil drain connects to a sanitary system that can surcharge, it must be connected so sewage cannot back up into it (7.4.6.4.(5)OBC Div. B 7.4.6.4. Protection from Backflow(1) Except as permitted in Sentence (2), a backwater valve that would prevent free circulation of air shall not be installed in a building drain or in a building sewer. (2) A backwater valve may be installed in a building drain provided that, (a) it is a "normally open" design conforming to, (i) CAN/CSA-B70, "Cast…). Our backwater valve guide explains backflow protection.

Common mistakes

  1. A loose lid. The cover must be child-resistant and airtight, not a loose plate.
  2. A pit that is too small. Less than 750 mm deep or 0.25 m² does not meet the code.
  3. Discharging next to the house. A dry well needs 5 m from the foundation, and water should flow away from the building.
  4. Sump water in the sanitary sewer. Many municipalities prohibit it.
  5. Missing valves. The discharge pipe needs a union and a check or backwater valve.

How to look it up yourself

Open Division B, Part 9 of the 2024 Compendium. Subsection 9.14.5. covers drainage disposal, and Article 7.4.6.3. covers sumps in the plumbing rules. Search terms that appear in the code text:

  • "Sump Pits" (9.14.5.2.)
  • "Drainage Disposal" (9.14.5.1.)
  • "Dry Wells" (9.14.5.3.)
  • "Sumps or Tanks" (7.4.6.3.)

Read the article in the code viewer alongside the plumbing sump article.

BCIN exam angle

Sump pit dimensions and the dry well distance are House exam questions, and the sump discharge valves come up on the Plumbing exams. Study the House chapter on excavation, dampproofing, footings and foundations, then try the free quiz on the House exam or Plumbing House exam page.

Based on the official 2024 Building Code Compendium on ontario.ca.

© King's Printer for Ontario, 2024. Reproduced with permission.

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Frequently asked questions

Is a sump pump required in Ontario?
Foundation drains must drain to a sewer, drainage ditch or dry well. Where gravity drainage is not practical, the code requires an automatic sump pump to lift the water from the sump pit to one of those places (Division B, Articles 9.14.5.1. and 9.14.5.2.).
How big does a sump pit have to be?
Where a sump pit is provided, it must be at least 750 mm deep and at least 0.25 m² in area, with a cover (Division B, Sentence 9.14.5.2.(1)).
What kind of cover does a sump pit need?
The cover must resist removal by children and be airtight, so soil gas such as radon cannot enter the house through the pit (Division B, Sentence 9.14.5.2.(2)).
Can a sump pump discharge into the sanitary sewer?
The code lets foundation drainage go to a sewer, ditch or dry well, but many Ontario municipalities do not allow clear water from foundation drains in the sanitary sewer and have their own sewer use by-laws. Ask your municipality where your sump may discharge.
Does a sump pump discharge need a check valve?
For a pumped storm sump, the discharge pipe needs a union and a check valve, pumped to above grade, or a union, check valve and shut-off valve. A pumped sump discharging to the drainage system needs a union, a backwater valve and a shut-off valve in that order (Division B, Sentences 7.4.6.3.(7) and (9)).