Guidance document number 50, Waste disposal units, Published February 2023 via Ceda.


Waste disposal units have long been an accepted tool for the hygienic disposal of food waste and operate by grinding the food waste into small particles in a flow of cold water before flushing them down the drain.

Recent legislation has changed the situation and waste disposal units can no longer be used in this way.


Water Industry Act 1991:

S111(1)(a) Water Industry Act 1991 provides that “no person shall throw, empty or turn, or suffer or permit to be thrown or emptied or to pass, into any public sewer, or into any drain or sewer communicating with a public sewer any matter likely to injure the sewer or drain, to interfere with the free flow of its contents or to affect prejudicially the treatment and disposal of its contents”.

These offences are now subject to the new Environmental Sentencing Guidelines.

Whilst the act has been in force for over 30 years, most water companies did not consider food waste to be injurious to the sewer and allowed it to be disposed of into the sewer providing it did not include Fats, Oils or Grease (FOG).  Indeed some food actually helped the sewage treatment process.

Environmental legislation

As part of the overall drive to reduce waste, legislation has been introduced to reduce food waste and to encourage recycling through such means as Composting and Anerobic Digestion.  The Environment (Wales) Act 2016, The Waste (Scotland) Regulations 2012 and the Food Waste Regulations (Northern Ireland) 2015 all now make it illegal to use waste disposal units to discharge food waste into the sewer in the devolved nations.  The Environment Act 2021 will also make it similarly illegal in England when the appropriate section comes into force following DEFRA consultation, which is expected to be in early 2024.

Waste Disposal Units and Dewaterers

Waste disposal units can still be used providing that the solid food waste in the output slurry is separated and collected for recycling by the use of a dewaterer.  This also has the benefit of reducing the volume of solid waste that needs to be stored prior to collection for recycling by up to 80%