Quick answer: Pressure washing generates wastewater containing suspended solids, hydrocarbons, cleaning chemicals, biocides and biological matter. Allowing that wastewater to enter a surface water drain, watercourse or groundwater without authorisation is an offence under the Environmental Permitting (England and Wales) Regulations 2016. Trade effluent — wastewater from commercial operations — cannot be discharged to foul sewer without consent from the sewerage undertaker. Mobile pressure washing contractors, vehicle cleaning operators, fleet wash facilities and drain jetting contractors all generate trade effluent that must be controlled. Enforcement by the Environment Agency is increasing.
Environmental Permitting is one of the most consistently overlooked compliance areas for pressure washing contractors. The focus in the sector is typically on equipment specification, COSHH and duty of care for waste chemicals — the wastewater itself is frequently treated as a secondary concern. But the wastewater generated by pressure washing — even where no chemicals are used — is trade effluent and is subject to specific legal controls on where it can go.
The legal framework
Three pieces of legislation govern wastewater from pressure washing operations:
- Environmental Permitting (England and Wales) Regulations 2016 — makes it an offence to cause or knowingly permit a water discharge activity without an environmental permit or exemption. A water discharge activity includes releasing polluting matter into surface water, groundwater or onto land where it could reach a watercourse.
- Water Industry Act 1991 — governs discharge of trade effluent to foul sewer. Trade effluent cannot be discharged to the public sewer without a trade effluent consent from the sewerage undertaker (typically Severn Trent, Thames Water, Yorkshire Water or similar). Domestic foul sewers are not designed or consented for trade effluent.
- Water Resources Act 1991 — makes it an offence to cause or knowingly permit polluting matter to enter controlled waters, which includes rivers, streams, groundwater and coastal waters. Polluting matter includes hydrocarbon-contaminated washdown water, detergent runoff and silt-laden water from surface cleaning.
The two drain types — and why getting it wrong matters
Most commercial sites have two types of drain:
- Surface water (storm) drains — carry rainwater directly to a local watercourse or soakaway. Surface water drains are not treatment systems. Anything discharged to a surface water drain goes directly to the environment. Pressure washing wastewater into a surface water drain is almost always an offence under the Environmental Permitting Regulations.
- Foul water drains — carry wastewater to the sewage treatment works. Discharge of trade effluent to foul sewer requires consent from the sewerage undertaker. A domestic foul connection at a commercial premises does not automatically confer trade effluent consent.
The practical problem for mobile pressure washing contractors is that surface water and foul drains look identical in a car park or yard. Assuming a drain is foul when it is surface water is a common mistake — and a potentially expensive one. Environment Agency enforcement includes unlimited fines, prosecution and clean-up costs.
Who this affects
- Mobile pressure washing contractors — vehicle washing, external building cleaning, car park and hard surface cleaning. The wastewater from every job is trade effluent.
- Fleet wash facilities — fixed or mobile fleet cleaning operations must have appropriate drainage and consent in place.
- Drain jetting contractors — wastewater and debris from drain jetting operations is trade effluent and must be contained and disposed of correctly.
- Softwash operators — biocidal washdown water from render, cladding and roof cleaning contains active biocidal substances. Discharge of biocide-containing wastewater to surface water is a serious environmental offence.
- Solar farm cleaning contractors — even pure deionised water carrying soiling from solar panels is trade effluent if it runs off to a drain or watercourse.
- Food production and hospitality cleaning — hot wash wastewater from food production environments contains fats, oils, detergents and biological matter requiring specific consent and treatment.
What contractors should do
- Identify drain types before starting work — ask the site manager or check site drainage plans. Do not assume. If in doubt, contain all wastewater.
- Contain and collect washdown water — temporary bunding, drain plugs and wet vacuums allow wastewater to be collected for licensed disposal rather than discharged to drain.
- Use a licensed waste carrier — collected trade effluent must be disposed of by a licensed waste carrier to an authorised facility. Your Duty of Care as a waste producer requires a waste transfer note.
- Check site permits — fixed wash facilities and some commercial sites have Environmental Permits or trade effluent consents in place. Confirm these are current and cover your activities before starting work.
- PFAS awareness — as PFAS restrictions tighten (see: PFAS in cleaning chemicals →), wastewater containing fluorinated surfactants from cleaning products is an increasing environmental liability.
Related guidance
Environmental Permitting and washdown runoff →
PFAS in cleaning chemicals →
Biocide labelling compliance →
Cleaning trade hub →
Fleet and logistics hub →
Facilities management hub →
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