percolation area septic tank lateral lines

What Are Septic Tank Lateral Lines and Percolation Areas

What are Septic Tank Lateral Lines?

Septic tank lateral lines are also known as percolation pipes. These are the perforated pipes that extend from the outlet of the septic tank below ground into the soil. The purpose of these lateral lines is to provide a network of pipes that the effluent from the septic tank runs through. As the effluent passes through these pipes it seeps out of the holes in the pipes and infiltrates into the soil. So ultimately the septic tank lateral lines or percolation pipes serve as a final disposal area where effluent infiltrates into the ground.

An Essential Part of a Standard Septic System

The lateral lines form an important part of any septic system. They are used for both domestic septic systems and commercial septic systems. Properly functioning lateral lines are an essential element of any septic system. If they are blocked or not working properly then the septic tank effluent has nowhere to go and a system can backup and fail.

septic tank percolation area

UK 2020 Septic Tank Guidelines

After the year 2020, every basic septic tank system in the UK must have septic tank lateral lines or a percolation area installed. Direct discharges into streams and watercourses will not be permitted. So, between now and 2020, if you have a septic tank with a direct outfall of effluent to a stream or watercourse you need to install a soakaway or percolation area.

Installing a percolation area or soakaway after a septic tank in an existing garden is not always easy. You need a large area of ground and it involves significant excavation and disruption.

An alternative solution is to install a domestic sewage treatment plant. If you install a sewage treatment plant in place of your septic tank then you can still have a direct discharge to a watercourse or drain. Replacing a septic tank with a sewage treatment plant is a far more cost-effective option than installing a large percolation area.

There are a range of options available from low cost sewage treatment plants to non-electric sewage treatment plants. When looking for a sewage treatment plant you should always look for excellent value coupled with a system that is certified to EN12566-3.

septic tank installation cost

How to Install Lateral Lines Correctly

When designing your percolation area or lateral line arrangement it is advisable to get expert advice. A badly designed percolation area can function poorly and result in effluent ponding on the ground surface. So, before you commence any works, speak to a professional, get a site survey done and then ensure the septic tank installer you get is experienced and fully insured.

The number of lateral lines installed is a function of

  • the number of people in the house or building
  • the type of soil in the area
  • the groundwater level

How to Install a System Without Septic Tank Lateral Lines

Septic tank lateral lines are normally required because the septic tank effluent is not treated to a high standard. A typical septic tank only has a treatment level of approximately 30%. In contract, a modern sewage treatment plant or aerobic sewage system has a treatment efficiency of >95%. Systems like the Biocell QuickOne have an even higher treatment standard of >98%, producing clean and clear effluent.

In many areas, environment agency and building control offices will allow you to have a direct discharge to a stream or a watercourse if you install a sewage treatment system. So, while a sewage treatment system is more expensive than a basic septic tank, you save a lot of cost by not needing to install lateral lines. Even if you have no access to a stream or watercourse and you need to install some lateral lines, you can install a smaller number after a sewage treatment plant because the effluent is much cleaner and it infiltrates into the ground much easier.

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