Average Septic Tanks Costs and How They Work in Ireland

The following is a brief guide outlining how septic tanks work and what they generally cost.


About Septic Tanks in Ireland

A septic tank system is made up of three components, the septic tank itself, the percolation area and the sub soil the effluent ultimately discharges into.

The tank itself can be made of fiberglass or plastic, both of which models are usually round shaped or cylinder shaped and is mainly used on sites with limited vehicular access. Concrete septic tanks are also available and are generally more popular and these are generally constructed in rectangular shapes.


Average Septic Tank Costs

The cost of a septic tank will ultimately be dependent on the size of the tank being installed. In Ireland a typical septic tanks cost is approximately €950.

Average 6 Person Sewage Treatment System Costs

It is important not to confuse a septic tank with a wastewater or sewage treatment system which generally has a cost ranging from €2,500 to €3,500 depending on the individual site requirements.



Septic Tank Certification

All septic tanks in Ireland must have EN12566-1 certification which also conforms to the Irish Standard – S.R.66.  The new septic tank certification contains the design population of the tank and images of the tank to allow the homeowner or builder confirm the tank is correct for a particular site.

How a Septic Tanks Works

Stage 1 – The Septic Tank

Waste water enters the septic tank through the pipelines leading from the dwelling. While sitting in the tank, the solids and the liquids that make up the waste water begin to separate by natural breakdown. The solids sink to the bottom forming the sludge layer and the lighter particles of waster rising to the top, forming a layer known as scum. The sludge is left behind and eventually begins to build up which is why a septic tank must be emptied every few years.

Stage 2 – The Percolation Area

The waste water is now up to 90% free of solid waste and known as effluent, flows into the second chamber in the tank. Here, due to pressure in the tank caused by the incoming waste water in the first chamber, the effluent flows out into the percolation area through a series of perforated pipes. Once the effluent flows out through the pipes, it then flows through a layer of gravel before it finally reaches the soil.

Stage 3 – The Sub Soil

This is the last stage of the septic tank process where the biological organisms in the soil treat the waste ensuring that it permeates down and eventually out of the soil, joining up with the water on the surface. This stage is probably the most important as it ensures that the waste is no longer a health or environmental hazard which is why extensive soil testing is carried out prior to a septic tank installation to ensure that the soil is suitable.