Your options on the type of system depend on what you have for onsite soils and what will be happening within the ​development.  In general, these are the most common options in Alberta:

The household plumbing collects the wastewater and sends it to the septic tank where it is separated into the three layers : sludge, scum and wastewater.  In a Pressure Distribution System, the effluent from the tank's 2nd chamber (effluent dosing chamber) is delivered to the treatment field using a pump and small diameter pvc lines with small orifices drilled into each line.  It acts much like an underground sprinkler system for your effluent. 


The advantage of a Pressure Distribution System is that it helps to ensure that the entire treatment field receives relatively equal distribution of effluent, eliminating over-saturation of just one area that can happen with a Gravity System.   Treatment fields receiving effluent via Pressure distribution have a smaller design footprint.  There are also more design options when using pressure distribution, and the treatment area could be located at a higher location than the A disadvantage of a Pressure Distribution System is the small orifices in the pipes (usually 1/8") can become clogged from mineral build-up over time and need to be flushed and cleaned occasionally.  


Examples of Pressure Distribution Systems with different field types are below. 


Sand (Raised) Mound Field (Pressure Distribution System required)

   -Sand, rock and pipe

   -Sand, rock, pipe and chambers

   -Sand, pipe and chambers

At-grade Field (Pressure Distribution System required)

   -Pipe and chambers

Buried Field (Gravity or Pressure Distribution System)

   -Sand/rock and pipe

   -Sand/rock, pipe and chambers
Open Discharge (Pressure Distribution Only)

Treatment Mound Construction
Sand mound construction
Sand mound construction
Sand mound construction
Treatment mound laterals
Finished sand mound (raised mound)
Finished sand mound (raised mound)
Finished sand mound (raised mound)

​Uses Pressure distribution only.  A pump in the effluent dosing chamber delivers the effluent to the mound system. Pressure distribution pipes are placed in a bed of aggregates or chambers with a 12” layer of sand below. The wastewater is pumped into the pressure distribution system and sprays into the sand layer, where aerobic bacteria cleans the water.

A sand mound receiving primary treated effluent (Type 1) must be above ground and must have a separation of three feet (AB, SK & MB) or two feet (BC) between the bottom of the sand layer and a restrictive layer or water table. Sand mounds receiving secondary treated effluent (Type 2) may have a reduced sand layer depending upon the regulatory requirements in the  jurisdiction in which it is installed.  Mounds must be landscaped with grass and be regularly maintained in order to have improved efficiency.


​Uses Pressure distribution only.  Similar to a raised mound field or a buried field, except the distribution lines are not buried.  The lines are placed on the ground, and covered with chambers, which are then covered with mulch to prevent freezing and damage.  


At-grade fields are an excellent option for areas with trees.  The lines can be woven through the trees in a snake-like pattern, eliminating the need to cut down trees on the property.  Because the lines are not buried, it is relatively easy to troubleshoot and maintain access if there is a problem. 


Disadvantages of this type of system is that you must have an Advanced Treatment System (upgrade from just a normal septic tank) (see Eco-Options section) which raises the cost of the overall system.  However, these costs can be balanced against having to remove trees or requiring major excavation.

At grade 1
At grade 3
At grade 2

A typical At-Grade will perform at a rate 4.3 times better than any subsoil absorption method. Within 2 – 6 years, the entire area of the At-Grade will become infiltrated by local flora and fauna, blending it in with the surrounding terrain. The efficiency of the At-Grade is expected to improve as time passes, decomposition and growth in the area aid in the absorption/distribution of water. Research indicates that At-Grades out perform all other methods of final treatment in high water table areas and tight clay soils. At-Grades perform best in treed areas where protection from wind and vehicles is greatest. The vegetation in the forest provides the best infiltration available. Areas with sloping terrain are preferred, but level areas are also acceptable.


​Uses Pressure OR Gravity distribution.  For Pressure Distribution, a pump in the effluent dosing chamber delivers the effluent to the distribution lines buried in a trench.  Pressure distribution lines are placed in a bed of aggregates or chambers not more than 24" below the surface.  The wastewater sprays into the gravel layer (or into the chambers) and is distributed into the in-situ soil for treatment.  Pictures to the right are examples of a different buried fields using Pressure Distribution.
Gravity Distribution in trenches normally uses 4" perforated sewer pipe, or chambers.  The effluent enters the trenches via gravity (not pressurized). 

Buried Pressure Distribution line
Buried Chambers

Uses Pressure distribution only.  Open Discharge systems are sometimes used on farms or acreages. In this system waste enters the septic tank and the wastewater is discharged through a pipe system onto the open property. There are strict provincial guidelines on size of property required to run a direct or open discharge as the discharge must occur a certain distance from the property line and any water source on the property or within a certain radius of the discharge. Talk with us to see if your development qualifies for an Open Discharge, or refer to the regulations for the jurisdiction the system is located in to obtain information on the requirements and restrictions regarding open discharge systems.


Like a Pressure Distribution System, the household plumbing collects the wastewater and sends it to the septic tank where it is separated into the three layers : sludge, scum and wastewater.  In a Gravity Distribution System, the effluent enters the treatment field via gravity (non-pressurized).


Gravity systems have been used for decades, and many are still in place today.   However, due to new regulations and advances in technology, most modern installations do not use gravity systems.  Gravity systems generally require a larger footprint for the treatment field.  They are prone to overloading zones and not distributing effluent equally throughout the treatment field.  


Most gravity systems will consist of a standard 2 compartment septic tank and a buried treatment field.  4" perforated sewer pipe is laid in drainrock in trenches and covered over.   Some may argue that a gravity system is less expensive than a pressure system.  While it is true that most gravity system configurations require less components and materials, the excavation costs are much higher due to larger field requirements.   Our designs take into account all factors and provide you with the best solution.


Hybrid systems can also be designed where a pump in the tank pumps the water to a distribution box in the field, and from the distribution box to weeping lateral trenches the effluent is distributed by gravity.  

Typical 2 chamber septic tank
Gravity Distribution
Gravity distribution
Gravity distribution
Typical Tank and Field
BBB - Septic System Design, Septic System Installation and Service

#19 SITE 10 RR1




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Finished sand mound (raised mound)