July 20, 2024
How Do Septic Systems Work

How Do Septic Systems Work

Most homes in urban areas may not require a separate sewage system unless renovations involving additional rooms for occupancy is required, even then, a link up to the public sewage system should be considered first as it is the best option. However, for those who have just purchased land in rural areas where waste water treatment has not been made available, this guide is intended to help such owners to install a feasible and practical septic system on their own.

Although, it requires some tough work, weighing the cost against a contractor to do this, the work would not matter much given the cost of a septic system installed by a contractor. Nevertheless, if the budget permits, then obviously getting a contractor to do it is advised, but if the budget is tight, this guide will help land owners save on money significantly by following the below steps.

System Preparation and Design

The first thing that land owners are required to do for a septic installation is to conduct a survey of the property to test the soil in the area. The septic system is to be designed based on the findings of the soil test after which the appropriate permits could be applied based on intended purposes and intended water use according to dwelling size and location of wells in the area.

This is critical towards layering soil types such as sand, rock or clay at relative depth as this is a critical factor towards the ability of the soil to filter and drain wastewater. Only after all this is determined should the design process start (after obtaining the necessary approvals and permits). After the design is complete this basically involves a septic tank and the piping that leads from the toilet to the septic tank and pipes from the septic tank to the ground.

Equipment and Tools

The equipment and tools that would be required include a mini excavator rental (mini excavators are available for hire on a daily basis and costs approximately 200AUD per day and for the installation of a septic tank with a mini excavator, the excavator will only be needed for a day.

Other equipment required include a grading pole (which is not necessary if the mini excavator has an internal ‘smart’ inbuilt grading system), 4 inch PVC pipes (lengths according to the distance between the home and the septic tank location), perforated pipes, vent caps and test caps, PVC primer and glue, hammers, saw, shovel, cement, septic filter and fabric, distribution box (if needed in the design).

The most cost effective septic tanks are the type that is powered by gravity, which means that the system uses gravity to work and thus the flow must go downhill all the way from the source to the septic tank and finally to the drain field. The angle should slant downhill using a pipe (4″ Sch. 40) about a foot under the footing to about five feet as it leads outside the building towards the tank at a minimum.

After the installations of the pipe ensure that a test cap is attached at the end that is into the building and seal any the holes that are made with hydraulic cement (both inside and outside). Remember the sloping of the pipe must be at an appropriate angle otherwise water which is more fluid would leave solids behind and eventually cause clogs.

Excavation for the Septic Tank

The excavation using a mini excavator should take no longer than an hour, hence if possible rent the excavator for about 2 hours if possible to excavate a hole that is large enough to place the concrete tank. Use the in-built grading system in the excavator if present, otherwise use a laser transit and “scan” the surface of the pipe leading to the tank.

The measurement should be from the distance from the top of the inlet all the way to the bottom-side of the tank. Add the measurement and add another 1 1/2″ to the measurement received from the first measurement from the top of the pipe to get the appropriate depth for the septic tank. Excavate the leeching field as afforded by the permit. Then use about an “inch-and-a-half” of gravel (washed drain rock) around the pipe to keep the pipe in place. Generally there are local health requirements that owners are required to comply with in regards to the size of embedment that is needed and as well as the size of gravel.

As for the perforated pipe in the draining field, it does not have to be sloped and the end of the pipe is capped. After the drain field pipes are installed, subject what has been done for inspection by the health inspector to get a green light before covering up the tank and pipes. In most places the general rules of septic tank installation will require compulsory special filter fabrics, about four inches of straw and newspaper to shield the draining rock layer prior to backfilling.


Among the most important things about installing septic tanks is related to the quality of materials that are used.

Good quality material is critical towards making sure that the septic tank lasts. Using manual labour to excavate is another factor that is unadvisable as things get messy and take significantly more time to dig, excavate and grade.

It is due to this reason that taking a mini excavator for hire is advised as everything will get done within a few hours with an excavator compared to a few days with manual labour.

These excavators also come with hydraulic attachments that could be rented separately in the event that during excavation land owners run into hard ground or rocks or tree roots that need to be pulled out.

 The excavator could also come in handy to move dirt and debris away from the site and also fill the entire area with soil quickly. In the event that a mini excavator is not available, then a standard excavator or even a backhoe would do the trick.

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