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Homeseptic’s guidance on the rules, regulations and planning laws for Septic Soakaways, Drainage Fields, and Rainwater Soakaways. 

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Homeseptic’s guidance on the rules, regulations and planning laws for Septic Soakaways & Drainage Fields 

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Soakaway Regulations

Soakaway Regulations relating to foul drainage state that a soakaway is no longer an acceptable method of discharge. Instead, a Drainage Field must be used. For Rainwater, a soakaway is still acceptable. Please see the next section for the difference between a Soakaway and a Drainage Field.

The law that governs the discharge of sewage discharge to the ground has changed. This new set of regulations came into force on the 1 of January 2015. If you are replacing your old discharge or are installing a new discharge it must be via a Drainage Field conforming to BS 6297: 2007. The works must be signed off by Building Control to ensure you have suitable evidence of compliance. Should you not have sufficient space to install a Drainage Field then you will need to gain a permit from the Environment Agency to discharge using an alternative method.

If you currently discharge to ground and this discharge existed before 1983, then as long as you comply with the other regulations and maintenance requirements of the 2015 General Binding Rules, you do not need to do anything until the existing discharge fails.

If your current discharge was installed between the 1st of January 1984 and the 31st of December 2014 then it needs to conform with the regulation in place at the time. Building Control sign-off for the works will be sufficient evidence. Should you not have this then you will likely face issues when coming to sell your property.

Do not worry if you do not fully understand the above please continue reading and we will furnish you with the information necessary to understand and assess your current situation. Soakaway regulation, rules, and the legal environment can seem really complicated. We have tried in this article to answer some of the common questions our customers have about the regulation. If you do not find what you are looking for please give us a call. Even if we do not know the answer straight away someone will get back to you.

This page will deal with Foul Soakaways and their modern equivalent Drainage Fields.  If you are interested in Rainwater Soakaways please follow this link 


What is the difference between a Soakaway and a Drainage Field?

Traditionally a Soakaway is an undefined hole in the ground filled with rubble or more recently rainwater crates. This type of solution is no longer permittable without an Environment Agency Permit. Further, as the discharge area is not designed specifically for the ground conditions they are often insufficiently sized. This leads to poor performance and short lifespans, as well as causing pollution.

A Drainage Field is a custom-designed discharge area. The area of the field is based on a percolation test. This ensures the size of the field is sufficient for your needs. The depth of the field is at most 700-800mm, this ensures aerobic contact allowing the discharge to receive further treatment. Further treatment allows for the further breakdown of suspended solids increasing the life of the discharge as well as causing less pollution.

The construction of a Drainage Field is a series of perforated pipe-laid trenches backfilled with 20mm gravel. The width of the trenches is prescribed, between 300mm and 900mm at a maximum. The pipes are laid no deeper than 700mm – 800mm in the ground. This ensures aerobic digestion can take place which allows the effluent to be treated. The minimum area covered by a drainage field is also prescribed by building regulations and ensures adequate drainage capacity. For more details on the design and construction please see this article

For a soakaway, liquid either from a septic tank or rainwater would enter the backfilled hole and drain away. The two main reasons a soakaway is no longer acceptable for foul drainage are as follows:

  • A Soakaway does not necessarily allow for the treatment of effluent. This creates harmful pollution.
  • There often is little science in the exact size, depth, and construction of a soakaway. This often leads to them not being fit for purpose.

The new laws and regulations for Soakaways & Drainage Fields

As of the 1st of January 2015, a new set of rules came into effect for all owners of off-mains drainage solutions. This included Septic Tanks, Sewage Treatment Plants, and Cesspits.  The Rules are known as the General Binding Rules for small sewage discharges. This moved the legal responsibility for adherence firmly to the individual house owner. If you have an off-mains drainage system then need to understand your responsibilities.  You also need to keep detailed records of what your system is and how it is maintained and serviced.

As of the 1st of January 2015 if you have a NEW soakaway installed for foul water it has to conform to BS 6297: 2007 and the installation must be signed off by building control. If you do not do this, without obtaining a permit from the EA then you are breaking the law and will also have to rectify this to sell your house. Please note that some dodgy companies are giving out compliance certificates with their non-drainage field installations. These are not valid, the rules are very clear and easy to understand, and it is your responsibility to adhere to them.

If you have an active soakaway, which can be demonstrated to have been active before 1983, then you do not have to do anything until it comes to replacing it. You still have to abide by the other General Binding Rules.

If it was installed between 1983 and 2015 you have to be able to demonstrate it met the standards in place at the time of installation. This can be demonstrated via the Building Control certificate obtained at the time of installation. Building Regulations for Drainage Fields were published in 2007. So effectively from 2007 the discharge will be expected to be a properly designed and installed Drainage Field.

For a more detailed review of the new rules please see the following article: New Soakaway and Drainage field regulations.

Do I already have a drainage field?

If you are asking this question then the answer is probably not. Most historic systems discharge to a soakaway, which is basically just a hole in the ground filled with rubble. This does not allow for the proper treatment of effluent which is why it is now illegal. If you are unsure we can come out free of charge and have a quick look.

What is a Drainage Field?

A Drainage Field is a system of infiltration pipes placed in trenches and arranged so that effluent can be discharged to the ground. The field must be constructed in a certain way that allows for the effluent to be treated in the soil through aerobic digestion. This means it must be constructed in the top 700-800mm of the soil to ensure aerobic contact.

The Field must be big enough to treat and disperse the maximum amount of discharge the system will discharge to it. This is calculated by a formula that we will examine below in this article. The two main variables needed to calculate this are first, Vp, a measure of soil porosity gained from a percolation test. Secondly, the population of the household or population rating of the tank is present in the system.

If a company comes to quote for a system, with a discharge to ground and does not require to undertake a percolation test then we would strongly advise you to discount their advice and quote. Without a percolation test, you cannot design a system that adheres to the Building Regulations or the General Binding Rules. Further, the system is unlikely to work properly.

The stages of a Drainage Field Installation

Below are the various stages of a good Drainage field installation. From the left. 

  1.  The Drainage Pipe is laid in a trench on top of the base layer of 20mm shingle.
  2. The Drainage Pipe is then covered with 20mm shingle
  3. The backfilled section is then covered in Taram to stop root and solid impregnation. 
Drainage Field on base layeer
Drainage field backfilled
Drainage Field covered

Do I need planning permission for a soakaway?

If you are installing a replacement Soakaway then you will generally not require planning permission. If you are installing a new foul Soakaway or drainage field you should at least inform your local planning office. For all types of Soakaway, Building Control guidelines are required to be followed. These are covered in the Building Regulations 2010 section H Drainage and Waste Disposal.

Permissions needed depend on the type of soakaway you are intending to build. For a septic soakaway, drain field, or Sewerage treatment plant soakaway, you will need planning permission if no system was historically in place. If the soakaway is a replacement then planning permission is not normally needed.

For a Rainwater Soakaway, you should consult your local planning agency. The rules that govern Rainwater soakaways depend on the water capture area in m2. For those serving an area of 25m2 or less than Part H of Schedule 1 to the Building Regulations 2010 applies.

The Building Regulations dictate an order of priority for the rainwater runoff from buildings these are:

  • an adequate soakaway or another adequate filtration system, or if not reasonably practicable,
  • a watercourse, or where not reasonably practicable,
  • an appropriate sewer

The key elements of the Part H rules are that the soakaway must be 5 meters from a building or road. A soakaway must be 2.5 meters from the boundary. The soakaway must not be in an area of unstable ground or where the lowest point of the soakaway meets the water table at any point of the year. The soakaway must not be near any other soakaway or drainage field, as this would compromise the absorption of the ground.

What are the regulations/ planning rules concerning Septic Soakaway or drainage field installation?

The most important rules concerning drainage fields are the 2015 General Binding rules, BS 6297:2007, and Building Regulations 2010 section H2. Please see our guide. 


 The detailed rules can be found here and explain all the permits and rules you will need to adhere to in relation to a septic tank drainage field. For the general binding rules please see here.

The sewage must:

  • be domestic in nature – contact the Environment Agency if you’re not sure
  • not cause pollution – find out how to check for pollution

Rules on checking for Pollution: Septic Tank

You must check the area where you release sewage once a month for signs of pollution.

If you release sewage into the ground, check for:

  • sewage smells
  • signs that your sewage isn’t draining properly (eg pools of water in the area where you release sewage)

If you release sewage into the water, check for:

  • sewage smells
  • overflowing sludge
  • signs of white scum or foam on the water around the area where you release sewage

Contact the Environment Agency incident line if you see signs of pollution at 0800 80 70 60. You should document your monthly checks.

In addition, You will need to apply for a permit if any of the following are relevant to your discharge.

  • to a well, borehole, or other deep structure
  • more than 2 cubic meters (2,000 litres) per day
  • in a groundwater source protection zone (SPZ1)

If you intend to release into surface water you will need to use a sewerage treatment plant.

How deep should a soakaway be?

The Perforated pipe should be laid at a minimum depth of 200mm and a maximum depth of 700mm. This enables aerobic contact between the effluent and the drainage stone and soil particles. This leads to aerobic digestion and effectively treats the effluent. Each drainage trench can be up to 30 meters in length. The trenches can be between 300mm and 900mm.

How long should a Soakaway last?

If installed correctly a drainage field for effluent should last for around 25 years at a minimum. A rainwater soakaway should last for far longer as long as the gutters are regularly cleaned and filtered.

Building and regulations for Cesspit soakaways.

A Cesspit is a sealed unit that does not discharge anything. Therefore it does not need a soakaway. If you were to try and create a DIY drainage field you would almost certainly be breaking the law. Please see our Cesspit guide

Soakaway Crates in Clay

In order for anything to soakaway in the ground, the ground needs to be able to drain. Clay soils typically do not drain very well and can in some cases be impermeable. This means that if you build a soakaway or put crates into the ground it will just sit there or drain away very slowly. What you need to do is carry out a percolation test. Please see our guide. This will enable you to scientifically calculate the number of crates, the size of the drainage field, or the soakaway you need. Without doing this you are just guessing.

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Soakaway Regulation
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Soakaway Regulation
Soakaway Regulations have changed. In 2015 the Environment Agency released a new body of legislation requiring all new discharges to the ground to be made via a Drainage Field. This article tackles this issue.
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