Class 1, 2 and 3 sewage systems: BCIN On-site Sewage Systems

Last updated October 22, 2026

Values this chapter turns on

max daily flow for a Class 2 or Class 3 system: 1,000 L/day; max daily flow for a Class 2 or Class 3 system
pit bottom above the high ground water table: 900 mm; pit bottom above the high ground water table
soil or fill required around privy and pit sides: 600 mm; soil or fill required around privy and pit sides
greywater per fixture unit with pressurized water: 200 L; greywater per fixture unit with pressurized water

Classes 1 to 3 are the small, simple systems: privies and other toilets that need no water (Class 1), greywater pits (Class 2), and cesspools (Class 3). They are common at camps, cottages and remote sites. Exam questions on them are mostly number lookups: 900 mm, 600 mm, 150 mm and 1,000 L/day come up again and again. The good news is that the same numbers repeat across the three classes.

Class 1: what it may receive

A Class 1 system is designed to receive only human body waste (OBC Div. B 8.3.1.2.(1)). Two extras are allowed where the system is designed for them: non-waterborne biodegradable kitchen wastes for biological decomposition, and small quantities of plant matter added to help decomposition (Sentence (2)). If a Class 1 system has a drain to remove excess liquid, it must drain to a Class 3, 4 or 5 system (Sentence (3)). Note that Class 2 is not on that list: greywater systems are only for greywater.

Class 1 systems are also the one class that needs no building permit (OBC Div. C 1.3.1.1.(1)(c)). They still have to meet Part 8.

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Class 1: privy superstructures

Earth pit privies, privy vaults and pail privies need a superstructure that (OBC Div. B 8.3.2.1.):

is built of strong, durable, weatherproof materials and is easily sanitized,
has a solid floor on a sill of treated timber, masonry or equal,
has seats with covers on an enclosed bench or riser lined with impervious material on all inside vertical surfaces (unless it is urinal only),
has a self-closing door,
has screened ventilation openings, and a ventilation duct screened at the top that runs from under the bench to above the roof,
has no other openings for receiving waste.

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Class 1: privy types

Type	Key construction rules
Earth pit privy (8.3.3.1.)	pit bottom at least 900 mm above the high ground water table; sides reinforced against collapse; at least 600 mm of soil or leaching bed fill on all sides and the bottom; earth mounded at least 150 mm around the base of the superstructure
Privy vault or pail privy (8.3.4.1.)	watertight container of easily cleaned material; earth mounded at least 150 mm; ground graded so surface drainage goes away from the privy
Portable privy (8.3.5.1.)	watertight receptacle that is easily emptied and cleaned; built to withstand transport and loading stresses

Definitions help you tell them apart: an earth pit privy is an excavation with a superstructure; a privy vault has a constructed vault that is emptied periodically; a pail privy has a removable container; a portable privy combines receptacle and superstructure in one unit (def., def., def., def.).

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Class 2: greywater systems

A Class 2 system treats and disposes of greywater only (OBC Div. B 8.4.1.2.(1)). Its daily design flow comes from the fixtures that drain to it:

Water supply	Flow per fixture unit
Pressurized	200 L
Not pressurized	125 L

A Class 2 system may not be built where the daily design greywater flow exceeds 1,000 L/day (OBC Div. B 8.4.2.2.).

Construction (OBC Div. B 8.4.2.1.): pit bottom at least 900 mm above the high ground water table; sidewalls built to prevent collapse, using open jointed material that lets the pit leach; a tight, strong cover kept on except when adding or removing greywater or for maintenance; earth mounded at least 150 mm around the perimeter; surface drainage diverted away; and at least 600 mm of soil with a percolation time under 50 min on all sides and the bottom.

Sizing the greywater pit

The sidewall loading rate may not exceed LR = 400 / T, in litres per day per square metre of sidewall (OBC Div. B 8.4.2.3.).

Step	Working	Result
Flow	4 x 200 L	800 L/day (under 1,000, so Class 2 is allowed)
Loading rate	400 / 20	20 L/m² per day
Sidewall area	800 / 20	40 m² of sidewall

If the same cottage had no pressurized water, the flow would be 4 x 125 = 500 L/day and the sidewall area 25 m².

Over the limit. With pressurized water, 6 fixture units give 1,200 L/day. That exceeds 1,000 L/day, so a Class 2 system is not permitted.

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Class 3: cesspools

A cesspool may not be built where the daily design sanitary sewage flow exceeds 1,000 L/day, and it may receive only the contents of, or effluent from, a Class 1 system (OBC Div. B 8.5.1.2.). It is not a place for toilet waste piped from a house.

Construction (OBC Div. B 8.5.2.1.) mirrors the greywater pit: bottom at least 900 mm above the high ground water table; sidewalls protected against collapse using open jointed material; a tight, strong cover; earth mounded at least 150 mm; drainage diverted away; at least 600 mm of soil or leaching bed fill around it, except at the top where it reaches the surface. One extra: where the cesspool extends to the ground surface, the cover must be lockable.

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Clearances for Classes 1, 2 and 3

Table 8.2.1.5. lists each system type in a row and gives four columns: a well with a watertight casing to at least 6 m; a potable-water spring or any other well; a lake, river, pond, stream, reservoir or non-potable spring; and a property line. Read across the row for your system.

Two values to anchor your reading: an earth pit privy needs 30 m from a well that lacks a 6 m watertight casing, and a cesspool needs 60 m from such a well. Every system in the table needs 3 m to a property line. Remember the rule from Chapter 6: where T is under 10 min, the well and water body distances must be increased.

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Common traps

900 mm above the high ground water table applies to earth pit privies, greywater pits and cesspools.
600 mm of surrounding soil applies to the same three; for greywater the soil must have T under 50 min.
150 mm mounding applies to all privies with a superstructure, greywater pits and cesspools.
1,000 L/day is the cap for both Class 2 and Class 3.
A Class 1 overflow drain goes to Class 3, 4 or 5, never Class 2.
Lockable covers are a cesspool rule, only where it extends to the surface.

Chapter review

Chapter at a glance

One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.

Chapter at a glance: the key idea in each section
Section	Key idea
Class 1: what it may receive	A Class 1 system is designed to receive only human body waste.
Class 1: privy types	Definitions help you tell them apart: an earth pit privy is an excavation with a superstructure; a privy vault has a constructed vault that is emptied periodically; a pail privy…
Class 2: greywater systems	A Class 2 system treats and disposes of greywater only.
Class 3: cesspools	A cesspool may not be built where the daily design sanitary sewage flow exceeds 1,000 L/day, and it may receive only the contents of, or effluent from, a Class 1 system.
Clearances for Classes 1, 2 and 3	Two values to anchor your reading: an earth pit privy needs 30 m from a well that lacks a 6 m watertight casing, and a cesspool needs 60 m from such a well.

Class 1: what it may receive
A Class 1 system is designed to receive only human body waste.
Class 1: privy types
Definitions help you tell them apart: an earth pit privy is an excavation with a superstructure; a privy vault has a constructed vault that is emptied periodically; a pail privy…
Class 2: greywater systems
A Class 2 system treats and disposes of greywater only.
Class 3: cesspools
A cesspool may not be built where the daily design sanitary sewage flow exceeds 1,000 L/day, and it may receive only the contents of, or effluent from, a Class 1 system.
Clearances for Classes 1, 2 and 3
Two values to anchor your reading: an earth pit privy needs 30 m from a well that lacks a 6 m watertight casing, and a cesspool needs 60 m from such a well.

Usual exam traps

900 mm above the high ground water table applies to earth pit privies, greywater pits and cesspools.
600 mm of surrounding soil applies to the same three; for greywater the soil must have T under 50 min.
150 mm mounding applies to all privies with a superstructure, greywater pits and cesspools.
1,000 L/day is the cap for both Class 2 and Class 3.
A Class 1 overflow drain goes to Class 3, 4 or 5, never Class 2.
Lockable covers are a cesspool rule, only where it extends to the surface.

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Questions on Class 1, 2 and 3 sewage systems, in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

Practice this chapter On-site Sewage Systems calculations

Code cited in this chapter

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

OBC Div. B 8.3.1.2. Application
(1)Except as provided in Sentence (2), a Class 1 sewage system shall be designed to receive only human body waste for disposal.
(2)Where the sewage system is specifically designed for the biological decomposition of non-waterborne biodegradable kitchen wastes or requires the addition of small quantities of plant matter to improve the decomposition of human body waste, it may receive such wastes in addition to human body waste.
(3)Where the sewage system is designed with a drain for the removal of excess liquid, then the sewage system shall drain to a Class 3, 4, or 5 sewage system.
Open OBC Div. B 8.3.1.2. in the code viewer
OBC Div. C 1.3.1.1. Requirement for Permits
(1)A person is exempt from the requirement to obtain a permit under section 8 of the Act,
(a)for the demolition of a farm building located on a farm,
(b)subject to Sentence (2), for the construction or demolition of a building in territory without municipal organization, or
(c)for the construction of a Class 1 sewage system.
(2)The exemption in Clause (1)(b) from the requirement to obtain a permit does not apply to the construction of a sewage system in territory without municipal organization.
(3)The application for a permit respecting the demolition of a building to which Sentence 1.2.2.3.(1) applies shall include descriptions of the structural design characteristics of the building and the method of demolition of the building.
(4)No person shall commence demolition of a building or any part of a building before the building has been vacated by the occupants except where the safety of the occupants is not affected.
(5)A tent or group of tents is exempt from the requirement to obtain a permit under section 8 of the Act and is exempt from compliance with the Code provided that the tent or group of tents are,
(a)not more than 60 m² in aggregate ground area,
(b)not attached to a building, and
(c)constructed more than 3 m from other structures.
(6)A shed is exempt from the requirement to obtain a permit under section 8 of the Act and is exempt from compliance with this Code, provided that the shed,
(a)is not more than 15 m² in gross area,
(b)is not more than one storey in building height,
(c)is not attached to a building or any other structure,
(d)is used only for storage purposes ancillary to a principal building on the lot, and
(e)does not have plumbing.
(7)A demountable stage or demountable support structure not regulated by Section 3.17. of Division B is exempt from the requirement to obtain a permit under section 8 of the Act and is exempt from compliance with this Code.
Open OBC Div. C 1.3.1.1. in the code viewer
OBC Div. B 8.3.2.1. Construction Requirements
(1)A privy as described in Subsections 8.3.3. to 8.3.5. shall be enclosed with a superstructure that
(a)is constructed of strong durable weatherproof materials,
(b)has a solid floor supported by a sill constructed of treated timber, masonry or other material of at least equal strength and durability,
(c)is easily sanitized,
(d)unless it is equipped solely as a urinal, is equipped with one or more seats each having a cover and being supported by an enclosed bench or riser that is lined with an impervious material on all interior vertical surfaces,
(e)is equipped with a self-closing door,
(f)has one or more openings for purposes of ventilation, all of which are screened,
(g)has a ventilation duct that is screened at the top end and that extends from the underside of the bench or riser to a point above the roof of the superstructure, and
(h)shall not have any openings for the reception of human body waste, other than urinals and those constructed in accordance with Clause (d).
Open OBC Div. B 8.3.2.1. in the code viewer
OBC Div. B 8.3.3.1. Construction Requirements
(1)An earth pit privy shall be constructed in the following manner:
(a)the bottom of the pit shall be at least 900 mm above the high ground water table,
(b)the sides of the pit shall be reinforced so as to prevent their collapse,
(c)the pit shall be surrounded on all sides and on its bottom by not less than 600 mm of soil or leaching bed fill, and
(d)the soil or leaching bed fill around the base of the sides of the superstructure of the earth pit privy shall be raised or mounded to a height of at least 150 mm above ground level.
Open OBC Div. B 8.3.3.1. in the code viewer
OBC Div. B 8.3.4.1. Construction Requirements
(1)A privy vault or a pail privy shall be constructed in the following manner:
(a)the container or structure that is to be used for the holding or storage of sanitary sewage shall be watertight and made of a material that can be easily cleaned,
(b)the soil or leaching bed fill around the base of the sides of the superstructure shall be raised or mounded to a height of at least 150 mm above ground level, and
(c)the surface of the ground in the area of the privy vault or pail privy shall be so graded that surface drainage will be diverted away from the privy.
Open OBC Div. B 8.3.4.1. in the code viewer
OBC Div. B 8.3.5.1. Construction Requirements
(1)A portable privy shall be constructed in the following manner:
(a)the portable privy shall have a watertight receptacle that shall be suitable for the holding and storage of any sanitary sewage deposited in it,
(b)the receptacle for the holding and storage of sewage shall be designed and constructed in such a manner as to allow it to be easily emptied and cleaned, and
(c)the portable privy shall be constructed of such material and in such a manner that it can withstand the stresses to which it will be subjected during its transportation to and from sites where it is to be used and during loading and unloading from vehicles used for the transportation of the portable privy to and from sites where it is to be used.
Open OBC Div. B 8.3.5.1. in the code viewer
OBC Div. A 1.4.1.2.(1) Earth pit privy
Earth pit privy means a latrine consisting of an excavation in the ground surmounted by a superstructure.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. A 1.4.1.2.(1) Privy vault
Privy vault means a latrine in which the receptacle for human waste consists of a constructed vault from which the waste is periodically removed.
Open OBC Div. A 1.4.1.2.(1) in the code viewer

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OBC Div. A 1.4.1.2.(1) Pail privy
Pail privy means a latrine in which the receptacle for human waste consists of a removable container surmounted by a superstructure.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. A 1.4.1.2.(1) Portable privy
Portable privy means a portable latrine in which the receptacle for human body waste and the superstructure are combined structurally into one unit.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. B 8.4.1.2. Application
(1)A Class 2 sewage system shall be designed only for the treatment and disposal of greywater.
(2)The total daily design flow for a Class 2 sewage system shall be calculated based on the fixtures discharging to the system as follows:
(a)200 L per fixture unit where there is a supply of pressurized water, and
(b)125 L per fixture unit where there is no supply of pressurized water.
Open OBC Div. B 8.4.1.2. in the code viewer
OBC Div. B 8.4.2.2. Maximum Sewage Flow
(1)A Class 2 sewage system shall not be constructed where the daily design greywater flow to the system exceeds 1,000 L/day.
Open OBC Div. B 8.4.2.2. in the code viewer
OBC Div. B 8.4.2.1. Construction Requirements
(1)The bottom of the pit shall be at least 900 mm above the high ground water table.
(2)The pit shall be constructed in such a manner as to prevent the collapse of its sidewalls.
(3)Any material used to support or form the sidewalls of the pit shall be an open jointed material of a type that will permit leaching from the pit.
(4)The pit shall be provided with a tight, strong cover that shall remain over the pit except when it is necessary to remove it for purposes of adding greywater to or removing greywater from the pit or for purposes of maintenance of the pit.
(5)The earth around the perimeter of the pit shall be raised or mounded to a height of at least 150 mm above ground level.
(6)The surface of the ground in the area of the pit shall be so graded that surface drainage in the area will be diverted away from the pit.
(7)The pit shall be surrounded on all sides and on its bottom by at least 600 mm of soil having a percolation time of less than 50 min.
Open OBC Div. B 8.4.2.1. in the code viewer
OBC Div. B 8.4.2.3. Sizing
(1)A Class 2 sewage system shall be designed and constructed so that the loading rate to the side walls shall be not more than the value calculated using the formula,
L_R = 400/T
where,
L_R = loading rate ofthesidewallsinlitresperday/m^2,and
T = percolation time.
Open OBC Div. B 8.4.2.3. in the code viewer
OBC Div. B 8.5.1.2. Application
(1)A Class 3 sewage system shall not be constructed where the daily design sanitary sewage flow to the system exceeds 1,000 L/day.
(2)A Class 3 sewage system shall be designed to receive only the contents of a Class 1 sewage system or effluent from a Class 1 sewage system for disposal.
Open OBC Div. B 8.5.1.2. in the code viewer
OBC Div. B 8.5.2.1. Construction Requirements
(1)The bottom of the cesspool shall be at least 900 mm above the high ground water table.
(2)The cesspool shall be constructed in such a manner as to prevent the collapse of its sidewalls.
(3)Any material used to support or form the sidewalls of the cesspool shall be an open jointed material of a type that will permit leaching from the cesspool.
(4)The cesspool shall be provided with a tight strong cover that shall remain over the cesspool except when it is necessary to remove it for the purposes of adding sanitary sewage to or removing sanitary sewage from the cesspool or for purposes of maintenance of the cesspool.
(5)Where the cesspool extends to the ground surface, the cover required in Sentence (4) shall be lockable.
(6)The soil or leaching bed fill around the perimeter of the cesspool shall be raised or mounded to a height of at least 150 mm above ground level.
(7)The surface of the ground in the area of the cesspool shall be graded such that surface drainage in the area will be diverted away from the cesspool.
(8)The cesspool shall be surrounded on all sides and on its bottom by at least 600 mm of soil or leaching bed fill, except the top where the cesspool extends to the surface of the ground.
Open OBC Div. B 8.5.2.1. in the code viewer
OBC Div. B Table 8.2.1.5. Clearance Distances for Class 1, 2 and 3 Sewage Systems — Forming Part of Sentence 8.2.1.5.(1)
Table 8.2.1.5. Clearance Distances for Class 1, 2 and 3 Sewage Systems — Forming Part of Sentence 8.2.1.5.(1) Sewage System | Minimum horizontal distance in metres from a well with watertight casing to a depth of at least 6 m | Minimum horizontal distance in metres from a spring used as a source of potable water or well other than a well with a watertight casing to a depth of at least 6 m | Minimum horizontal distance in metres from a lake, river, pond, stream, reservoir, or a spring not used as a source of potable water | Minimum horizontal distance in metres from a property line Earth Pit Privy | 15 | 30 | 15 | 3 Privy Vault | 10 | 15 | 10 | 3 Pail Privy | 10 | 15 | 10 | 3 Greywater System | 10 | 15 | 15 | 3 Cesspool | 30 | 60 | 15 | 3
Open OBC Div. B Table 8.2.1.5. in the code viewer