Guidance

Domestic sewage: discharges to surface water and groundwater

Updated 29 July 2021

You need to classify your waste water when you apply for an environmental permit or to know whether your activity qualifies for an exemption. You will need to find out what your discharge contains to know whether it’s classed as domestic sewage.

Domestic sewage includes waste waters arising from normal domestic activities. ‘Domestic activity’ takes account of both the nature and scale of the activity. Domestic activities can be carried out at any site, for example schools, restaurants, takeaways, holiday parks and nursing homes.

You should not need to carry out a detailed investigation to determine if a discharge contains trade effluent.

Type of activity

Domestic sewage includes waste water from:

• toilets
• personal washing, showering and bathing
• household washing using domestic detergents
• cooking at home for family and friends
• commercial cooking for sale directly to consumers, such as a restaurant or sandwich bar – includes consumption on and off site
• washing dishes and cooking equipment, on a scale comparable to domestic cooking, after using them on the premises
• swimming pools at homes and hotels where they are provided free for residents and when the effluent is treated and discharged in combination with other domestic sewage effluent

Effluent from other sources is not domestic sewage, for example:

• chemical toilets – at residential or commercial sites
• washing at commercial premises of items received from off site – for example campsite launderettes open to non-residents, high street launderettes, centralised laundries for hotel chains
• commercial cooking – food processing or cooking and packaging food for sale off site
• municipal or commercial swimming pools

Waste water discharges from hospitals, vets, schools and universities have domestic or trade aspects depending on their activities. For example, a small hospital may only discharge domestic sewage, while a larger hospital may have a range of non-domestic effluent.

If a significant proportion of the effluent you discharge is different from that found in a normal home it’s classed as a mixture of domestic sewage and other effluent. It is:

• trade effluent if it comes from a commercial premises
• other polluting matter if it comes from private residential premises

A discharge of swimming pool drain down or backwash water which is discharged separately from other sources of domestic sewage is not classed as domestic sewage. This is because the effluent is significantly different from that found in a normal home.

Scale of activity

You need to consider the scale of your activity.

For example, producing 30 jars of jam in a day is a domestic activity even if some or all of those jars are then sold elsewhere. However, regularly producing 300 jars a day for sale is classed as a trade.

Similarly, butchering the occasional carcass in a restaurant or farm shop is a domestic activity. However, butchering dozens of animals each day is classed as a trade.

If you change your activities the category of your waste water may change. In this situation, you may need to apply for a permit or vary your existing permit.

Permits for your discharge

If your discharge is classed as domestic sewage, you may need a:

• permit or have to meet the general binding rules for septic tank or small sewage treatment plant
• standard rule permit for package treatment plants: SR2010 number 3

If your activity does not meet the conditions of the general binding rules or the standard rule, you will need to apply for a bespoke permit.