Class 1 sewage systems: pit privies specifications

How should I build a proper privy or Class 1 sewage system?

Strong durable weatherproof materials are required.

The bench and floor should have a very slight grade to facilitate the flow of cleaning water. This grade could be 1/8 to 1/4 of an inch. The absence of a door plate allows for quick, easy sweeping and mopping of the privy.

By using half-round moulding in the corner behind the bench and at the base of the bench, a no-wax floor covering can be placed in one piece from the front of the privy across the floor, up and over the bench and two feet up the back wall. This seals the floor and bench and creates an easily cleanable surface. The side walls could also be covered part of the way up with no-wax floor covering to improve cleaning.

The use of windows and a clear fiberglass roof will allow adequate lighting for safety and cleaning purposes.

All inside walls should be flat and smooth.

The inside of the bench should be covered with a heavy gauge plastic to waterproof the complete area.

Spring loaded hinges are required for the door to meet the requirement of a “self-closing door”.

What other considerations should I follow?

When constructing the pit frame, some builders extend one corner of the superstructure into the pit and use this as a corner of the pit and the frame. This prevents people from pushing the privy over.

The use of a flat roof versus a peaked roof gives the benefit of two fewer corners for hornet nests.

Some designs incorporate an extended roof plus modesty panels to allow the use of a urinal.

When constructing a privy for a family, some designs include accommodations for children, such as:

two benches at two different heights
the use of a step or stool
smaller bench hole and seat

A privy which is well vented, properly located, constructed to facilitate easy cleaning and is well lighted will serve the needs of all without complaint or inconvenience.

How can ventilation problems be prevented?

The pit should have air movement to prevent any long-term buildup of odours. This may be accomplished by a large pipe with a “whirly-gig” on the top which both draws out the stale air and replaces it with fresh air. The pit may also be vented by using two pipes of different heights to create air movement inside the pit. Usually the higher pipe is also the deepest pipe which would be the first to pick up wind currents and direct the flow into the lower part of the pit, while the shorter pipe returns the stale air from the upper portions of the pit to the atmosphere.
Cross ventilation is required from all sides at the top. To create complete movement of air, two small bottom vents are recommended in order to supply ventilation to the floor and seat area.
Choose a location for your privy that is well ventilated and exposed to the prevailing winds. This will allow all of the above ventilation practices to operate at a maximum.
Completely seal the superstructure from the pit. Toilet seats are a problem because the nobs on the seat and lid create an air gap which results in ventilating inside the privy. The nobs should be removed and completed rings of weather welting installed so that the seat is sealed to the bench and the lid makes a complete seal when closed.

What is a privy or Class 1 sewage system under the Ontario Building code?

The Ontario Building Code is the minimum legal requirements for class 1 sewage systems (Pit Privies).

Section 8.3 Class 1 Sewage Systems

8.3.1. General Requirements

8.3.1.1. Scope

This section applies to the construction of a Class 1 sewage system.

8.3.2. Superstructure Requirements

8.3.2.1 Construction requirements

A privy as described in Subsections 8.3.3. to 8.3.5. shall be enclosed with a superstructure that:

is constructed of strong durable weatherproof materials
has a solid floor supported by a sill constructed of treated timber, masonry or other material of a least equal strength and durability
is easily sanitized
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 which is lined with impervious material on all interior vertical surfaces
is equipped with a self closing door
has one or more openings for purposes of ventilation, all of which are screened
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
shall not have any openings for the reception of human waste, other than urinals and those constructed in accordance with Clause (1)(d)

8.3.3. Earth pit privy

8.3.3.1. Construction requirements

An earth pit privy shall be constructed in the following manner:

the bottom of the pit shall be at least 900mm (36 inches) above the high ground water table
the bottom of the pit shall be reinforced so as to prevent collapse thereof
the pit shall be surrounded on all sides and on its bottom by not less than 600mm (24 inches) of soil or leaching bed fill
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 150mm (6 inches) above ground level

Minimum distance from a drilled well	15m (50 feet)
Minimum distance from a dug well	30m (100 feet)
Minimum distance from a lake, river, etc.	15m (50 feet)
Minimum distance from a property line	3m (10 feet)

Once the daily sewage flow (DSF) has been determined it is then necessary to determine what the percolation time, T of the soil is, this is needed in order to calculate how big of a pit to construct. By using the formula T x DSF / 400 we will then come up with the area of the side walls of the pit in m2 that is required.

Note that the bottom of the pit is not included in determining side wall area.

As mentioned earlier, the pit shall be constructed in such a manner as to prevent the collapse of its sidewalls, this can be done in a number of ways such as using concrete blocks to line the pit, filling the pit with large size rocks, (size of a fist or larger), or by placing plastic 45 gallon drums drilled with holes in the pit and covering these with sand.

The top of the pit now must be covered, if the construction of the pit is for example concrete blocks, this can be accomplished with any strong material such as wood or patio stones covering the blocks. Soil would be added to cover the top and would be done in such a manner as to mound the top of the pit to shed water. A drain line coming from the building would be directed into the center of the pit.

This item was last modified on July 21, 2015