Our Engineers Design Greywater Leaching Pits

Our Licensed Professional Engineers design Greywater Leaching Pit (Greywater Pit) - a Class 2 Sewage System for a fee of $795⁺ʰˢᵗ. If inevitably required, Site Visit, Soil Sampling, and Lab Analysis of the Soil Sample incur additional costs.

Greywater Leaching Pit (Greywater Pit) - a Class 2 Sewage System - can only be used for the treatment and disposal of greywater derived from plumbing fixtures such as kitchen sinks, showers, laundry tubs, and bathtubs (wastewater not containing human body waste). A Greywater Leaching Pit (Greywater Pit) is satisfactory for the disposal of greywater when the daily amount of such waste is small, and site conditions are suitable.

A Greywater Leaching Pit (Greywater Pit) is regulated under the Ontario Building Code (OBC). A Greywater Leaching Pit (Greywater Pit) is designed to treat and dispose of greywater when there is the presence of a sanitary drainage system in a structure.

When considering the location for a Greywater Leaching Pit (Greywater Pit), caution must be taken to ensure that the minimum setbacks are strictly adhered to. These distances are stated as minimum requirements and may have to be increased if the soil conditions are not ideal.

A Greywater Leaching Pit (Greywater Pit) should be constructed in an area that is elevated and well-drained. Low-lying areas that are subject to excessive surface run-off, promoting saturated soils, may overload the greywater pit, resulting in very poor greywater treatment and increasing the possibility of groundwater contamination.

Ontario Building Code - 8.4.1.2.(2)

A Class 2 sewage system shall not be constructed where there is a supply of pressurized water.

The total daily design flow for a Greywater Leaching Pit (Greywater Pit) shall be calculated based on the fixtures discharging to the system as follows:

125 Litres per fixture unit where there is no supply of pressurized water.

Under the Ontario Building Code (OBC), a Greywater Leaching Pit (Greywater Pit) can only be used if the daily design sewage flow is less than 1,000 Litres per day.

The Ontario Building Code requires that if you are constructing a Greywater Leaching Pit (Greywater Pit), the following requirements must be met:

The bottom of the Greywater Leaching Pit (Greywater Pit) shall be at least 900mm above groundwater or bedrock.

The Greywater Leaching Pit (Greywater Pit) shall be constructed in such a manner as to prevent the collapse of its side-walls.

Any material used to form the side-walls of the Greywater Leaching Pit (Greywater Pit) shall be an open-jointed material of a type that will permit leaching from the Greywater Leaching Pit (Greywater Pit).

The Greywater Leaching Pit (Greywater Pit) shall be provided with a tight, strong cover that shall remain over the Greywater Leaching Pit (Greywater Pit) except when it is necessary to remove it for purposes of adding sewage to or removing sewage from the Greywater Leaching Pit (Greywater Pit), or for purposes of maintenance of the Greywater Leaching Pit (Greywater Pit).

The earth around the perimeter of the Greywater Leaching Pit (Greywater Pit) shall be raised to a height of at least 150mm above the surrounding ground level.

The surface of the ground in the area of the Greywater Leaching Pit (Greywater Pit) shall be graded so that the surface drainage in the area will be diverted away from the pit.

The pit shall be surrounded on all sides and on its bottom by at least 600mm of soil having a percolation rate (T) greater than 1 or less than 50.

Better treatment, drainage, and evaporation are achieved in the soil that is just below the surface. The bottom of the Greywater Leaching Pit (Greywater Pit) must be a minimum of 900mm above the high water table or bedrock. Because the grey water sewage is treated by the bacteria in the soil, it is important to have 900mm of unsaturated soil to provide adequate treatment and to protect against contamination. The top 20 to 50mm of soil will filter all solids in the grey water sewage. The remaining sewage bacteria will be treated by the soil bacteria as the liquid moves down through the soil.

When installing a leaching Greywater Leaching Pit (Greywater Pit) in clay soils, the excavation must have 600mm of clean sand between the crushed rock and the clay soil. The sand will filter the suspended solids and treat the grey water to provide a higher quality effluent that will be more easily absorbed by the clay soil. Before placing the sand in the excavation, the walls and bottom of the Greywater Leaching Pit (Greywater Pit) must be raked to remove smeared clay soils and allow more contact area with the sand, to improve the drainage abilities of the clay soil.

When the Greywater Leaching Pit (Greywater Pit) is completed and ready to be covered, it is recommended that the fill be crowned slightly to shed rainwater and snow melt. A thin layer of topsoil and sodding will prevent erosion, assist with evaporation, and divert surface water away from the Greywater Leaching Pit (Greywater Pit). The final grade must be sodded.

Since the Greywater Leaching Pit (Greywater Pit) does not have a settlement tank, it may be necessary to install a grease interceptor or a screen. The grease interceptor is required if kitchen wastes are going into the Greywater Leaching Pit (Greywater Pit). The grease interceptor will allow for the cooling of the wastewater and separation of the fats, oils, and grease. A convenient pest-safe access to the grease interceptor to remove the contents of the interceptor during cleanups as required, and the contents can be disposed of in the composter or household garbage. The installation of a screen before the Greywater Leaching Pit (Greywater Pit) will significantly reduce/prevent the entry of solids into the Greywater Leaching Pit (Greywater Pit).

The contents trapped in the screen should be removed regularly and disposed of in the composter or household garbage. Similar to a Septic tank, a Greywater Leaching Pit (Greywater Pit) and a grease interceptor shall be pumped out regularly. If solid materials build up in the Greywater Leaching Pit (Greywater Pit) it is a good idea to have them removed; this will prolong the working life of the Greywater Leaching Pit (Greywater Pit).

For Additional Information, please contact one of our key design team members:

Miaoyi Xue, P.Eng.

Joo Min Park, MEng, P.Eng.

Saloni Khoja, B.Arch.

Wei Ming Lin, P.Eng.

Rui Cong Xia, P.Eng

Liu Sun, B.Des (Arch)

Pamela M. Jerezano, B.Arch.

LAND DEVELOPMENT EXPERTS

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Our Dedicated Specialized Land Development Experts offer  Municipal/Civil Engineering Services including Site Plans, Functional Servicing Reports, Site Servicing Plans, Site Grading Plans, Drainage Plans, Erosion & Sediment Control Plans, Stormwater Management Reports, Septic System Design and Structural Engineering Designs to obtain Site Plan Approvals, for new construction, additions, renovations alterations, and interior fit ups, and Subdivision Approval in all the Regions. Counties and Municipalities in Ontario, including 

City of Brantford, City of Chatham-Kent, Haldimand County, City of Hamilton, City of Kawartha Lakes, City of Toronto

REGIONAL MUNICIPALITIES

Durham

    City of Oshawa, City of Pickering, Municipality of Clarington, Town of Ajax, Town of Whitby, Township of Brock, Township of Scugog, Township of Uxbridge

Halton

    City of Burlington, Town of Halton Hills, Town of Milton, Town of Oakville

Niagara

    City of Niagara Falls, City of Port Colborne, City of St. Catharines, City of Thorold, City of Welland, Town of Fort Erie, Town of Grimsby, Town of Lincoln, Town of Niagara-on-the-Lake, Town of Pelham, Township of Wainfleet, Township of West Lincoln

Peel

    City of Brampton, City of Mississauga, Town of Caledon

Waterloo

    City of Cambridge, City of Kitchener, City of Waterloo, Township of North Dumfries, Township of Wellesley, Township of Wilmot, Township of Woolwich

York

    City of Vaughan, Town of Aurora, Town of East Gwillimbury, Town of Georgina, City of Markham, Town of Newmarket, City of Richmond Hill, Town of Whitchurch-Stouffville, Township of King

COUNTIES

Dufferin

    Town of Grand Valley, Town of Mono, Town of Orangeville, Town of Shelburne, Township of Amaranth, Township of East Garafraxa, Township of Melancthon, Township of Mulmur

Elgin

    City of St Thomas, Municipality of Bayham, Municipality of Central Elgin, Municipality of Dutton/Dunwich, Municipality of West Elgin, Town of Aylmer, Township of Malahide, Township of Southwold

Hastings

    City of Belleville, City of Quinte West, Municipality of Centre Hastings, Municipality of Hastings Highlands, Municipality of Marmora and Lake, Municipality of Tweed,  Town of Bancroft, Town of Deseronto, Township of Carlow/Mayo, Township of Faraday, Township of Limerick, Township of Madoc, Township of Stirling-Rawdon, Township of Tudor & Cashel, Township of Tyendinaga, Township of Wollaston

Northumberland

    Municipality of Brighton, Town of Cobourg, Municipality of Port Hope, Municipality of Trent Hills, Township of Alnwick/Haldimand, Township of Cramahe, Township of Hamilton

Oxford

    City of Woodstock,  Town of Ingersoll, Town of Tillsonburg, Township of Blandford Blenheim, Township of East Zorra-Tavistock, Township of Norwich, Township of South-West Oxford, Township of Zorra

Peterborough

    City of Peterborough, Township of Asphodel-Norwood, Township of Cavan Monaghan, Township of Douro-Dummer, Township of Havelock-Belmont-Methuen, Township of North Kawartha, Township of Otonabee-South Monaghan, Township of Selwyn, Municipality of Trent Lakes

Simcoe

    City of Barrie, City of Orillia, Town of Bradford West Gwillimbury,  Town of Collingwood,  Town of Innisfil, Town of Midland, Town of New Tecumseth, Town of Penetanguishene, Town of Wasaga Beach, Township of Adjala-Tosorontio, Township of Clearview, Township of Essa, Township of Oro-Medonte, Township of Ramara, Township of Severn, Township of Springwater, Township of Tay, Township of Tiny

Wellington

    City of Guelph, Town of Erin, Town of Minto, Township of Centre Wellington, Township of Guelph-Eramosa, Township of Mapleton, Township of Puslinch, Township of Wellington North.

County of Perth

City of Stratford, Municipality of North Perth, Town of St. Marys, Township of Perth East, Township of Perth South, Municipality of West Perth

County of Middlesex

City of London, Municipality of North Middlesex, Municipality of Southwest Middlesex, Municipality of Thames Centre, Township of Adelaide Metcalfe, Township of Lucan Biddulph, Township of Middlesex Centre, Township of Strathroy - Caradoc, Village of Newbury

County of Huron

Municipality of Bluewater, Municipality of Central Huron, Municipality of Huron East, Municipality of Morris-Turnberry, Municipality of South Huron, Town of Goderich, Township of Ashfield-Colborne-Wawanosh, Township of Howick, Township of North Huron

County of Bruce

Municipality of Arran Elderslie, Municipality of Brockton, Municipality of Kincardine, Municipality of Northern Bruce Peninsula, Municipality of South Bruce, Town of Saugeen Shores, Town of South Bruce Peninsula, Township of Huron-Kinloss

County of Grey

City of Owen Sound, Town of The Blue Mountains, Town of Hanover, Municipality of Meaford, Township of Chatsworth, Township of Georgian Bluffs, Municipality of Grey Highlands, Township of Southgate, Municipality of West Grey

County of Haliburton

Township of Algonquin Highlands, Municipality of Dysart et al, Municipality of Highlands East, Township of Minden Hills

District of Muskoka

Town of Gravenhurst, Town of Bracebridge, Town of Hunstville, Township of Muskoka Lakes, Township of Lake of Bays, Township of Georgian Bay

Class 1 Sewage System - Privies

Privies: “Porta-Potty”(Portable Privies), Outhouses (Earth Pit Privies), Vault Privies

For human waste only

Typically, in either remote or temporary locations

Earth Pit Privy can only be used for the disposal of human body waste. Earth Pit Privy must not receive any greywater or any other wastewater derived from plumbing fixtures such as kitchen sinks, showers, bathtubs, washing machines, or laundry tubs.

A Greywater Leaching Pit (Greywater Pit) is often used in conjunction with an Earth Pit Privy system.

An Earth Pit Privy system does not require a building permit. Typically, an Earth Pit Privy system is used in remote areas, such as isolated cabins, seasonal use cottages, parks, or for temporary purposes, such as construction sites, where running water may not always be readily available.

The Earth Pit Privy (outhouse) is likely still the most commonly used sewage waste disposal structure in use today. Even though there have been several new developments in recent years, this basic yet effective installation is inexpensive to build and operate. If properly built, the Earth Pit Privy can last for decades and can serve as a backup to any conventional septic system when the guests arrive for the summer holidays.

Division B, Article 8.3.2.1 of the Ontario Building Code (OBC) outlines 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 in constructed in accordance with Clause (1)(d).

An Earth Pit Privy is only suitable where there is a sufficient thickness of soil above either bedrock or the high groundwater table.

Article 8.3.3.1 of Division B of the Ontario Building Code (OBC) outlines Construction Requirements for an Earth Pit Privy

(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 groundwater table,

(b) The sides of the pit shall be reinforced to prevent their collapse of them,

(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.

A Vault Privy is suitable where there is not adequate soil available to dig an earth pit privy.

Article 8.3.4.1 of Division B of the Ontario Building Code (OBC) outlines Construction Requirements for a Vault Privy

(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 graded so that surface drainage will be diverted away from the privy.

A Portable Privy combines into one unit the receptacle for human body waste and the superstructure. Therefore, this combined unit needs to have structural rigidity.

Article 8.3.5.1 of Division B of the Ontario Building Code (OBC) outlines Construction Requirements for a Portable Privy

(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.

The convenience of having an indoor toilet without the expense of a full-blown septic system has generated a growing market for cottage owners seeking more modern technology. Sometimes used for sleep camps (bunkies), these alternatives are often influenced by the overburden content (soil and ground cover) and topography of a property, as well as easy access for pump-outs.

Even though other types exist, the most common alternatives to the old traditional outhouse fall into three primary categories: composting toilets, incinerating toilets, and chemical toilets. Typically, installing these toilets does not require a permit.

In very simplistic terms, the Composting toilet relies on aerobic bacteria for decomposition so sewage must be aerated to optimize its effectiveness. The Incineration toilet utilizes electricity, natural gas, or propane to heat the raw sewage, boiling away liquids and converting residue to a powdery, sterile ash. The Chemical toilet utilizes potent chemicals such as sodium hydroxide or lye to burn and corrode organic tissue, liquefying the solids while killing the bacteria.

Class 3 Sewage Systems

Cesspools

Used for the treatment of sanitary sewage from a Class 1 sewage system

Have a short life and are not recommended unless all other possibilities for treatment have been rejected

Under the Ontario Building Code, a Class 3 sewage system is an underground pit (cesspool) used exclusively to treat and dispose of human waste, specifically from Class 1 sewage systems like composting toilets or outhouses. They cannot receive greywater (sinks, laundry, or showers) or raw blackwater directly from a standard indoor flush toilet. Because human waste quickly clogs soil and poses severe groundwater contamination risks, cesspools have a very short lifespan and are generally discouraged or rejected for new builds.

Class 3 sewage systems (cesspool) are best used in conjunction with a separate Class 2 system, like a Greywater Leaching Pit (Greywater Pit) used for greywater waste. Class 3 sewage systems (cesspool) are not designed to handle waste flows other than toilet waste. It is, essentially, an outhouse without the above-ground structure.

Usually used in addition to a Class 2 Greywater Leaching Pit (Greywater Pit), a Class 3 sewage system - an underground pit (cesspool) can only be used to dispose of waste from a Class 1 sewage system, like an Earth Pit Privy. Some models of composting toilets are equipped with an overflow device, or, where a pail privy is being used, a Class 3 sewage system - an underground pit (cesspool) may be installed.

Like the Class 2 Greywater Leaching Pit (Greywater Pit), the Cesspool method of sewage disposal can only be used if the daily sewage flow is less than 1,000 litres per day. For the traditional cottage, the anticipated daily sewage flow would be considerably less than this limit. In order to calculate the expected daily overflow from a composting toilet, we require the manufacturer's specifications to calculate the anticipated overflow on a day-to-day basis.

When constructing a cesspool, the Ontario Building Code stipulates that:

The bottom of the cesspool shall be at least 900mm above the high groundwater table.

The cesspool shall be constructed in such a manner as to prevent the collapse of its sidewalls.

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.

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 maintenance of the cesspool.

Where the cesspool extends to the ground surface, the cover required shall be lockable.

The soil or leaching bed fill around the perimeter of the cesspool shall be raised or mounded to a height of at least 150mm above the surrounding ground surface.

The surface of the ground in the area of the cesspool shall be so graded that surface drainage in the area will be diverted away from the cesspool.

The cesspool shall be surrounded on all sides and on its bottom by at least 600mm of soil or leaching bed fill, except the top where the cesspool extends to the surface of the ground.

A composting toilet, equipped with an overflow pipe, or a pail privy, shall have the  following clearance distances:

A well with a water-tight casing to a depth of at least 6 m (Drilled Well): 30m

A Spring used as a source of potable water or a well other than a water-tight casing to a depth of 6m (Shallow Well): 60m

A lake, river, pond, stream, reservoir, or spring not used as a source of potable water: 15m

A property line: 3m

Cesspools are generally discouraged because the human waste added to the cesspool will cause the soil to clog, which can reduce the life expectancy of the cesspool, and for anyone considering utilizing a cesspool, we strongly encourage them to explore other methods of sewage disposal.

The Ontario Building Code | Clearance Distances for Class 1, 2, and 3 Sewage Systems

8.2.1.5. Clearance Distances for Class 1, 2, and 3 Sewage Systems

(1) Except as provided in Sentences 8.2.1.4. (1) and (2), no Class 1, 2, or 3 sewage system shall have a horizontal distance of less than that permitted by Table 8.2.1.5.

Table 8.2.1.5.

Clearance Distances for Class 1, 2, and 3 Sewage Systems

Forming Part of Sentence 8.2.1.5.(1)

Earth Pit Privy

Minimum horizontal distance in metres from a well with watertight casing to a depth of at least 6 m: 15m

Minimum horizontal distance in metres from a spring used as a source of potable water or a well other than a well with a watertight casing to a depth of at least 6 m: 30m

Minimum horizontal distance in metres from a lake, river, pond, stream, reservoir, or a spring not used as a source of potable water: 15m

Minimum horizontal distance in metres from a property line: 3m

Privy Vault / Pail Privy

Minimum horizontal distance in metres from a well with watertight casing to a depth of at least 6 m: 10m

Minimum horizontal distance in metres from a spring used as a source of potable water or a well other than a well with a watertight casing to a depth of at least 6 m: 15m

Minimum horizontal distance in metres from a lake, river, pond, stream, reservoir, or a spring not used as a source of potable water: 10m

Minimum horizontal distance in metres from a property line: 3m

Greywater System

Minimum horizontal distance in metres from a well with watertight casing to a depth of at least 6 m: 10m

Minimum horizontal distance in metres from a spring used as a source of potable water or a well other than a well with a watertight casing to a depth of at least 6 m: 15m

Minimum horizontal distance in metres from a lake, river, pond, stream, reservoir, or a spring not used as a source of potable water: 15m

Minimum horizontal distance in metres from a property line: 3m

Cesspool

Minimum horizontal distance in metres from a well with watertight casing to a depth of at least 6 m: 30m

Minimum horizontal distance in metres from a spring used as a source of potable water or a well other than a well with a watertight casing to a depth of at least 6 m: 60m

Minimum horizontal distance in metres from a lake, river, pond, stream, reservoir, or a spring not used as a source of potable water: 15m

Minimum horizontal distance in metres from a property line: 3m