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Waste codes

20 03 04: Septic tank sludge

Code 20 03 04 is the absolute non-hazardous entry for septic tank sludge. The source system still needs to be confirmed, particularly where unusual inputs may have entered the tank.

Waste code referenceTechnical sources

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List of Waste code
20 03 04
WM3 entry type
Absolute non-hazardous
Official description
Septic tank sludge
Jurisdiction note
WM3 GB reference; check national requirements for the site

Septic tank sludge under 20 03 04

WM3 lists 20 03 04 for septic tank sludge and classifies it as an absolute non-hazardous entry. The description is tied to the source of the waste, so it should not be used for every liquid collected by a sewage tanker or every material removed from an underground tank.

The system type and the source of the material should be confirmed from reliable site information. A local name for a tank is not enough if it is unclear whether the waste is actually septic tank sludge.

Waste classification and site hazards

An absolute non-hazardous entry does not mean the work is free from other hazards. Sewage and tank work can involve biological exposure and confined spaces, which are controlled separately from the waste classification.

Off-site movement still has to meet the carrier, documentation and receiving-site requirements that apply in the relevant jurisdiction, with an accurate description of the waste.

Unusual inputs to the system

Industrial chemicals, unusual cleaning wastes or other atypical inputs may mean the material no longer fits the septic tank sludge description and needs a different code or assessment. The source should be checked rather than assuming every collection from a tank is routine septic sludge.

Product information, incident history and analytical results, where available, can help resolve uncertainty about what has entered the system and how the waste should be described.

Collection records for septic tank sludge

Useful records identify the tank location and system type, the collection date and quantity where known, and the carrier and receiving facility. Emptying the tank is separate from assessing a drainage field or repairing other parts of the drainage system.

Sources and further reading

Published by Environmental Services. Sources checked 12 September 2026. Editorial standards for this library.

If you identify a factual error in this library, please contact us so we can check it against the source.

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