Information to support your septic tank or other small sewage discharge registration

If your discharge is to a sensitive location (e.g. within 1.5km of a designated bathing water) you may need to reduce the amount of harmful bacteria it contains, such as E.coli. This is sometimes called "additional" or "tertiary" treatment.

Bacteria reducing treatment usually involves installing a filtration system that uses biological material or ultraviolet light. If it's required for your discharge, you should consult a professional drainage contractor about the available options.

Domestic properties include houses and individual caravans.

If you're applying to register a discharge from domestic properties only, you'll need to tell us the number of properties using the sewage treatment system.

Dilution is when a discharge of sewage effluent is mixed with water and becomes weaker.

To make sure that the environment won't be harmed, there needs to be enough water in a river, stream, or burn to properly dilute any sewage that discharges into it.

If this isn't the case for your discharge to water, you may need to move your discharge point or discharge to a soakaway instead.

A full soakaway is a sealed system of gravel filled trenches that allows all the treated sewage effluent that discharges into it to filter into the surrounding land. It is sometimes referred to as "infiltration system".

Mound soakaways are a specific type of full soakaway, built above ground in areas where digging trenches may be too difficult. For example, where bedrock is close to the surface.

Before building a soakaway, you will need to contact your local authority to arrange for a building warrant.

Mean Low Water Spring (MLWS) is a term that's used to describe how far the sea goes out at low tide. The lowest point a tide will normally reach is marked on an Ordnance Survey (OS) map as MLWS.

Sewage outfalls to the sea should ideally be located beyond this point so that they will always be underwater. If your discharge point is closer to the shore than MLWS, you may be required to move it further out to sea.

Non-domestic properties include commercial premises such as cafes, caravan sites, holiday cottages, hotels, and offices.

If you're applying to register a discharge from non-domestic properties only, or from a mix of domestic and non-domestic properties, you'll need to tell us the population equivalent value.

Population equivalent (p.e.) is a term that describes how much wastewater a single person will produce in a day.

To work out the p.e. of your non-domestic discharge, please read our guidance how to work out population equivalent for a non-domestic property.

If you're calculating the p.e. of a discharge from a mix of domestic and non-domestic properties, SEPA considers a single domestic property to be equivalent to five p.e. regardless of its size.

A partial soakaway isn't the same as a full soakaway. It is normally a single trench with an overflow into a watercourse.

Instead of holding all the effluent discharged from a treatment system, treated sewage flows through the partial soakaway where some of it will filter into the land. The final discharge is from the overflow into the water.

Phosphate sensitive areas are at risk of significant nutrient enrichment, which can be caused by sewage discharges. This can lead to environmental damage like harmful algal blooms.

In Scotland, the catchments of Loch Leven (Perth and Kinross), the Lunan Lochs (Perth and Kinross) and Loch Flemington (Highland) are considered phosphate sensitive.

If your discharge is located within one of these catchments you must apply for a licence. Read our guidance on how to apply for a licence to discharge sewage effluent.

A Private Water Supply (PWS) is any supply of water that isn't provided by Scottish Water. Most commonly they are supplies that are intended for human consumption (i.e. drinking water).

If you know that your discharge is close to a PWS, you need to confirm the precise location and type of the supply by contacting the Environmental Health department of your local authority.

When you have this information, you should contact us for further advice before you make an application.

The public foul sewer or mains sewer is a network of pipes that carry raw sewage to wastewater treatment works. The public sewer is owned and maintained by Scottish Water.

SEPA won't authorise your discharge if your property is close enough to connect to the public sewer. Instead, you should contact Scottish Water to ask about making a connection.

If your discharge is to a full soakaway, you must have the results of a soil percolation test to be able to complete your application. Performing a percolation test is time-consuming and should be carried out by a specialist drainage contractor.

The resulting soil percolation value (Vp) is a measure of how long it takes liquid to filter through the surrounding soil.

Further information on percolation value, including how to measure it, is available in the Scottish Government Building Standards Technical Handbook.

A septic tank is the simplest type of sewage treatment system. It works by holding sewage so that the solids sink to the bottom of the tank, and liquids flow out of an overflow at the top.

The liquid produced usually needs to be filtered before it can be released into the environment.

A secondary treatment system, sometimes referred to as a package treatment plant, is a sewage treatment system that treats sewage to a higher standard than a septic tank.

Secondary treatment will normally be required when a discharge is to a watercourse or is located within a sensitive environment.

Shellfish harvesting areas are parts of sea lochs where shellfish can be farmed or collected for human consumption. Shellfish from these areas need to pass health standards set by Food Standards Scotland.

You can find out more about shellfish harvesting areas on the Marine Scotland website.

If your discharge is to a shellfish harvesting area, you may not be able to complete your application online.