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Septic Systems

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Sewage System Maintenance Inspection System


The proper treatment and disposal of sewage is an essential element of our high standard of health and welfare in Ontario. Many bacterial and viral diseases, which less than a century ago frequently reached epidemic status, have been drastically reduced or eliminated through advances in sanitary engineering. Today sewage disposal is not something that most people living in municipally serviced areas of Caledon often think about. Public sanitary sewer systems and sewage treatment plants virtually eliminate the need for public concern.

In areas without sanitary sewers, sewage disposal is the responsibility of each property owner. Residential, commercial, and industrial property owners alike must treat and dispose of sanitary sewage and waste water on their property. To this end, a properly designed, constructed and maintained on-site private sewage disposal system will function effectively and safely for many years. A poorly designed or constructed system, or one that is not properly maintained can be dangerous to health, damage the environment and be costly to repair.

The purpose of this section of the website is to familiarize you with the operation and maintenance of your on-site sewage disposal system. Also, provided are the requirements for permit application and approval if you are installing a new system, or replacing or repairing an existing system.

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The Law Relating to On-site Private Sewage Disposal

The standards for on-site sewage disposal systems discharging 10,000 litres and less are prescribed by the Building Code Act and the Ontario Building Code.

In the Town of Caledon, the installation requirements listed in the Ontario Building Code are administered by the Building and Support Services Section.

The Building Code Act requires that any new development serviced by on-site sewage disposal, or any alteration to an existing system or building that may impact on an existing on-site sewage disposal system be undertaken only with a permit issued by the Chief Building Official. This includes additions to your home, accessory buildings, and swimming pools. Aside from the legal requirement to do so, it is in your best interest to contact the Building and Support Services Section to discuss your building plans because your construction project may be influenced by the location of your sewage disposal system. The Ontario Building Code requires a sewage system to be completed and operational prior to occupancy of any building.

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Fundamentals of On-site Private Sewage Disposal

For the purpose of private sewage disposal, sanitary sewage includes liquid or water borne waste of industrial or commercial origin, or of domestic origin, including toilet, shower, tub, laundry or kitchen waste. Other sources of water such as rain water leaders, downspouts, eavestroughs, weeping tiles, and sump pump discharges are considered to be storm sewage and must not be discharged to a private sewage disposal system.

Sewage created within your home is discharged into a tank at the exterior. After treatment in the tank the liquid portion known as 'effluent' is discharged to a disposal, leaching, or tile bed where additional treatment and final disposal occurs. This is explained in more detail later in this booklet.

The successful operation of an on-site sewage disposal system depends on the volume of sewage produced and the suitability of the soil to absorb the effluent (liquid waste).

The daily sewage flow from a house or dwelling is estimated according to various factors, including the number of bedrooms, the side of dwelling, the flow from the plumbing fixtures, and the type of soil located on site. In the case of industrial or commercial development the daily flow is determined from the use.

The design criteria for on site sewage disposal systems is found in the Ontario Building Code. All installers (contractors) employed in the business of installation or design of on-site sewage disposal systems in the province of Ontario must be licensed with the Ministry of Municipal Affairs and Housing. In certain circumstances, a professional consulting engineer must be hired by the property owner or developer to design the sewage system.

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Approval Process

  • Size the System
    Following a calculation of the sanitary sewage volume (daily design flow) of the building, a soils analysis is required. The analysis, completed by a geotechnical engineer will show the percolation capacity of the soil (known as the percolation time or T-time). Using the daily design flow, soils analysis, and the requirements listed in the Ontario Building Code, a design can be completed.
  • Submit your Design
    The design to be submitted for permit review and approval is required to include the following.
    • 2 copies of a site plan (scaled map) showing the sewage system, any structures on the property, wells, watercourses, property lines, etc. and measurements to those features
    • The soils analysis showing the T-time
    • A fully completed 'Application Form and Certificate of Approval For a Sewage System'. The application form can be completed by the property owner or an authorized agent acting on behalf of the owner. 
  • Starting Installation
    If the design is acceptable, a certificate of approval is issued allowing construction of the sewage system to begin. If the sewage system is being constructed to service a new building or building addition, a permit can now be applied for.
  • Inspection
    Before covering any part of a sewage system, an inspection and approval is to be obtained from a Town of Caledon Building Inspector. As an example, the following is a list of the sewage system components required to be inspected in a Class 4 system: the sewage system area; the contact area as used in a raised system; the septic tank(s); pump chamber, pumps, and pump controls/alarms; leaching bed piping; and a final grading inspection.

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Types of Private Sewage Disposal Systems

There are several varieties of private sewage disposal systems in common use in Ontario. This section is to provide sewage system owners with the basic understanding of the most common type of sewage system used and how it operates. To determine the type of sewage system on your property, please refer to your certificate of approval.

Primary Sewage Treatment

An on site private sewage disposal system generally consists of two parts; a septic tank or treatment unit which receives the untreated sewage from the house or building, and a leaching or disposal bed which introduces the liquid portion of the sewage into the soil.

Class 4 System

The Class 4 system has the widest range of applications and can be configured as an in ground or raised leaching bed or filter bed system. The operation of these variations are as follows: 

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Septic Tank

The main function of the septic tank is to remove solids and grease from the raw sewage that would otherwise plug the leaching bed. Suspended solids in the raw sewage are settled out in the first compartment of the septic tank and the liquid portion of the sewage flows through to the second compartment. Anaerobic (without oxygen) bacterial action breaks down much of the solid matter to liquids and gases. If the septic tank is working and maintained properly, only liquid waste should be discharged to the leaching bed system.

Sludge (settled solids) and scum (floatables) accumulate over time in the septic tank and must be periodically removed and properly disposed of to safeguard efficient operation of the septic tank. You should contact a licensed contractor by consulting your yellow pages under "septic tanks" and have your system inspected at least once every two years.

The bacterial action in a septic tank produces odours. The septic tank, however is normally vented back through the house sanitary drainage venting system to open air at the plumbing stacks.

Septic tanks are sized according to the daily design flow of the building. A septic tank must have a capacity of double the daily design flow for residential occupancies and triple the daily design flow for non-residential. Despite the daily design flow, septic tanks can have a capacity of no less than 3600 litres.

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Leaching Bed

Installation of leaching beds in native soils are allowable only if ground conditions permit (see raised leaching beds). The leaching bed is comprised of a number of lengths of perforated piping placed in carefully prepared trenches. The liquid sewage effluent passes through the pipe into the soil where further treatment by aerobic (with oxygen) bacteria takes place.

Raised Leaching Bed

In areas with high groundwater conditions, shallow bedrock, or poorly pervious natural soils, porous soils must be imported to construct a raised leaching bed. Soil must also be imported to construct a mantle which extends from the raised leaching bed piping to a distance of 15m in any direction which sewage is likely to flow after it has moved through the raised leaching bed. The maximum slope off the sides of a raised leaching bed is 4 units horizontally to 1 unit vertically. The distances to property lines must also be increased if a raised leaching bed is used.

Filter Beds

A filter bed consists of distribution piping placed on a continuous layer of stone above an approved sand filter medium. A filter bed concentrates the application of sewage effluent in a smaller area than a trenched leaching bed. Consequently, the need for a sound mantle around the filter to absorb effluent as it moves through the filter bed is critical.

Pumps, Siphons, and Distribution Boxes

When the total length of the leaching bed is 150 metres or more a pump or siphon must be installed in a separate tank. The purpose of the pump or siphon is to ensure that effluent reaches all parts of the leaching bed. A pump or siphon also permits the leaching bed to rest between doses and assists in preventing the leaching bed from freezing during extremely cold weather. An effluent pump may also be required for any leaching bed which is higher in elevation than the septic tank or treatment unit. A good quality effluent pump will last for many years, but as with all mechanical devices, it will eventually fail. A high level alarm should be installed to warn of a pump failure.

A distribution box may be used to assist with balancing the flow of effluent to each length of the leaching bed. If a distribution box is used, it should be placed on a compacted foundation to ensure that it is kept level. A split header may also be used to distribute effluent. A split header is a secondary header connecting to the main header of the leaching bed. The split header helps distribute effluent to the entire main header.

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Care and Maintenance of a Sewage System

A sewage system should, with proper care and maintenance, provide many years of service. There are, however, some things which you, the sewage system owner, should be aware of that will help the system to function.

The area over the leaching bed should have a good cover of grass, good ventilation and adequate sunlight. When landscaping, remember not to add soil to the leaching bed. Vegetable gardens, particularly root crops are not recommended over a leaching bed. Trees and shrubs should not be planted in the immediate vicinity of the leaching bed as root proliferation can disrupt and block the leaching bed piping. In addition, structures such as patios, sundecks, and tool sheds cannot be erected over your leaching bed.

Water usage should be kept to a minimum. Excessive waste water taxes the ability of the leaching bed to dispose of liquid sewage and could flush solids from the septic tank to the leaching bed. An automatic irrigation system should not be installed on or around leaching beds. Surface water should also be diverted away from leaching beds. These two factors can saturate a leaching bed and cause the system to malfunction.

Moderate use of household drain solvents, cleaners, or disinfectants should not interfere with the operation of the sewage disposal system. Indiscriminate use, however, may cause problems. Other chemicals such as paint thinners, pesticides, and herbicides should never be poured down the drain. These chemicals will contaminate ground water. Vehicular traffic should not be allowed over the leaching bed. Vehicles may cause soil compaction and damage to the piping.

Your septic tank should be inspected every 2 years and the tank pumped out when necessary (approximately every 4 years). Failure to pump out a septic tank will allow sludge or scum to be carried into the leaching bed piping. The final result of not maintaining your septic tank will be failure of the system. Regular maintenance of the septic tank is well worth the effort.


Under no circumstances should anyone enter a septic tank. Noxious gases which are heavier than air remain in the tank after the top is removed, and have caused death to both the original victim and to those who have attempted to rescue the first victim.

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Should you experience a problem with your on site sewage disposal system, such as sewage effluent discharging from the leaching bed to the surface of the ground, you must notify the Building and Support Services Section immediately. Arrangements with a licensed on site sewage system installer must be made to have your system repaired. As an owner/operator of a sewage system you are responsible by law to properly maintain and operate your system. The Building Code Act considers a malfunctioning system to be an unsafe condition.