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Soakaway Regulations – What Are They and Why Do They Matter?



Rules and building regulations for a soakaway relating to foul drainage state that a soakaway is no longer an acceptable method of surface water and drainage waste disposal. Instead, a drainage field must be used for anything that is not rainwater. When using a soakaway for rainwater, it must be located over five meters from a building, and two and a half meters from a boundary. Soakaways must also not come into contact with the water table, as well as having sufficient storage capacity; allowing the water to absorb into the soil before overflowing.

Building Regulations on Drainage Soakaway

Soakaways are a traditional surface water drainage system for buildings that are far away from a public sewer or watercourse, and are usually suitable for areas of less than 100 square meters. They are typically formed from square, or circular, pits filled with rubble or lined with dry jointed masonry or perforated concrete ring units. When dealing with a larger area, a soakaway generally uses a lined pit, trench type soakaways, or are constructed from specialist proprietary units. 

Soakaway building regulations state that they must have capacity to store immediate run-off from roofs and other hard surfaces, leading to the water being able to disperse into the surrounding soil efficiently enough to be able to cope with the next large amount of water. 

What are the Soakaway Regulations and Rules Installation?

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

Soakaway rules on checking for septic tank pollution:

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. 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 surface water you will need to use a sewerage treatment plant.

For further information on these rules, please visit the UK Government approved document.

For general binding rules concerning this topic, visit the UK Government approved document.

The Differences Between Soakaways and Drainage Fields:

A septic or rainwater soakaway is typically an undefined hole in the ground filled with rubble or rainwater crates, whereas a drainage field is a series of perforated pipes laid in trenches 300mm to 900mm wide, and backfilled with 20mm of gravel. The trenches used for drainage fields are usually a maximum of 700mm deep. This ensures aerobic digestion can take place, allowing effluent to be treated.

Installation of a soakaway

For a soakaway, liquid from surface run-off, rainwater, or septic tanks, would enter the backfilled hole and drain away. There are two main reasons why soakaways are no longer acceptable for foul drainage: 

  • There is little knowledge in the exact size, depth, and construction of the perfect soakaway, which often leads to them being unfit for purpose. 
  • Soakaways do not typically allow for the treatment of effluent, which creates harmful pollution.  

What are the Current Laws for Soakaways?

As of 01/01/2015, rules known as the General Binding Rules for small sewage discharges came into effect for all owners of off mains drainage solutions, which includes septic tanks, sewage treatment plants, and cesspits. These rules and regs allow for exceptions for old septic tanks but not for how long they discharge. These rules moved the legal responsibility for adherence firmly on the individual house owner – so if you have an off mains drainage system, you need to understand your responsibilities and the soakaway building regs. You also need to keep detailed records on what your system is, how it is maintained, and how it is serviced. 

  • If you discharge into the ground, then you have to do so via a drainage field. If you do not, then you will need to install one, or apply to the government agency for a permit to discharge. 
  • Systems that discharge to a watercourse or drainage ditch were given until 01/01/2020 to conform to the new rules. Rules also immediately came into effect for those discharging into the ground. It is now illegal to discharge to any of these outputs using a Septic Tank. As well as any method that does not meet the current standard for small sewage treatment plants
  • If you are discharging into the ground and come to sell your property, the soakaway will need to comply with these rules and regulations. 

Do I Need Planning Permission for a Soakaway?

If you are installing a new foul soakaway or drainage field, then you should inform your local planning office. However, if you are installing a replacement soakaway; then you will generally not need planning permission. 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, found here.