New 2020 Regulations For Septic Tanks - General Binding Rules

New Septic Tank Rules 2020 - Environment Agency General Binding Rules

These are very important if you are selling a house with a septic tank. Your system must comply, no matter how old it is.

Options under the New Septic Tank Regulations, if your Septic Tank discharges into a watercourse:

There are currently 3 options available:

  1. Connect to a main sewer. This is not usually an answer, as if a Main Sewer is available, you wouldn't have a septic tank anyway.
  2. Install a Drainage Field, but they would not work in most areas of the UK, as the natural soil drainage is too poor. The site would fail the Trial Site Assessment Hole and the Percolation Tests. You probably would not have a large enough garden, even if the soil passed the tests.
  3. The only option for most people is replacing the septic tank with a sewage treatment plant which treats the wastewater, producing a clear liquid that is non-polluting and which can be discharged into a watercourse legally. All WTE sewage treatment plants have the Certification required to replace existing septic tanks that discharge to streams and ditches. They are all extremely efficient, when compared with others and very cheap to run, with a non-electric option as well.

Options if your Septic Tank disharges into a Soakaway:

Under the new septic tank rules, most existing Septic Tanks and associated Soakaways are also no longer acceptable under the Environment Agency General Binding Rules. If you are selling your house, then the soakaway will need to be upgraded to a Drainfield at the point of sale.

The septic tank and type of soakaway in the diagram below would not meet current standards under these Rules. 

Septic tank illegal soakaway

Your Options would be:

  1. Install a correct Drainage Field, if you have enough land which also passes the Trial Site Assessment Hole and Percolation Tests. A typical Drainage Field requires up to 180 square metres of land and all of it has to be 15 metres from a building.
  2. If you have a ditch or other watercourse or surface water drain nearby, it is always cheaper to install a Sewage Treatment Plant and connect to the watetercourse instead of installing the Drainfield.

All sewage effluent discharges, irrespective of age, volume or location, are now subject to Environment Agency General Binding Rules. This also applies to existing septic tanks and sewage treatment plants and to the replacement of existing tanks and drainage fields.

As the ‘operator’ of a septic tank or small sewage treatment plant you must check you comply with all the general binding rules. You must apply for a permit if you don’t.

Septic tank effluent cannot be discharged into any watercourse or ditch.  If you have a septic tank that discharges directly to a surface water pipe, ditch, stream or river, you will need to replace or upgrade your treatment system within 12 months maximum, or when you sell your property, if before this date, under these new rules.

No rainwater is allowed into the system and the installation of new drains can be very expensive when you sell your property.

The fines for non-compliance are unlimited.

Why your sewage system might not comply with the new Septic Tank General Binding Rules

In the old days, when the soakaway drainfield failed, it was much cheaper to dig an overflow pipe to the ditch, or divert the septic effluent into a land drainage pipe that flows into a ditch, than to install a new one. However, this has been illegal, (even for existing systems) since 1991 when the Water Resources Act came into being to protect our ditches, streams and rivers. The maximum fine is now unlimited, so it is not worth the risk. In any case, if your septic tank discharges into a ditch you must do something about it before 1 January 2020 under the new General Binding Rules.

Any existing old permissions you may have, will only apply to discharge to a soakaway drainfield, not to the overflow to a ditch.

Only sewage treatment plants which have an EN12566-3 Certificate are allowed to discharge into ditches and watercourses. If you have a ditch running next to your property, you may be surprised to know who owns it. If the hedge or fence is at YOUR side, then you own the ditch at the other side. See Hedge and Ditch Law. soakaway crate

The Environment Agency has stated that soakaway crates are NOT acceptable for foul water soakaways as they do not conform to the Building Regulations, the General Binding Rules or the BS 6297 2008. Crates (see the photo on the right) are only designed for rainwater soakaways. Report the rogue traders to Trading Standards.

New or replacement septic tank soakaways are not allowed in a Groundwater Source Protection Zone 1. so always check that you are not in one before you buy a house with an existing septic tank, or before you consider buying a new septic tank.

At the planning stage it is essential to bear in mind that establishing a practical and legal method of discharging sewage effluent is more important than the actual septic tank or sewage treatment plant that will be installed and it should not be viewed as a reserved matter. We have had cases where a building plot was sold with full planning permission, only for the buyer to find out, after purchase, that no sanitation is possible at all - a very expensive piece of waste ground with a mortgage attached!

Effluent Disposal Methods

 discharging sewage effluent


Quality of the Discharged Effluent


It is important to remember that the effluent discharged from a septic tank or sewage treatment plant, no matter how well treated, is not clean water. It is sewage effluent and presents a risk to people and the environment due to the bacteria and viruses still present.

Strong consideration should be given to the quality of effluent that you discharge.

Even though a septic tank can be discharged to ground via a soakaway drainage field, it is often preferable to install a sewage treatment plant over a septic tank because of its effluent quality. The soakaway drainage field lasts much longer, as the soil is not constantly being clogged by the suspended solids in the liquor.

All drainage fields will fail over time and the worse the quality of the effluent the quicker it will fail due to blocking from suspended solids and anaerobic bacterial biomass caused by the effluent BOD (Biological Oxygen Demand).

Not all sewage treatment plants are equal in terms of their effluent quality.

Effluent quality is usually described by three measures of pollutants – Biological Oxygen Demand (BOD), Suspended Solids and Ammonia.  Each pollutant is measured in mg / Litre  (parts per million).


BOD 10
Suspended Solids 15
Ammonia (NH3) 10

The lower the figures, the better the effluent quality.


Downloads on sewage discharges

Discharging sewage effluent to ground

Sewage sludge, humanure and biosolid contamination of land