Environmental Permitting — Pressure Washer Runoff and Water Discharge Law

Environmental Permitting — pressure washer runoff and water discharge law

Pressure washing generates contaminated runoff — water containing detergents, degreasers, biocides, oil, fuel residue, paint, and other substances from the surfaces being cleaned. What happens to that runoff is governed by several pieces of UK environmental legislation. This is one of the most commonly misunderstood areas of compliance for cleaning contractors and facilities teams.

This page covers England and Wales. For Scotland see SEPA and Scottish trade effluent compliance →. For Northern Ireland contact NIEA.

The legislation that governs wash-down runoff

Water Resources Act 1991 (WRA) — Section 85 makes it a criminal offence to cause or knowingly permit polluting matter to enter controlled waters. Wash-down water containing detergents, oil, fuel or biocides is almost always polluting matter. Discharge to surface water drains is a criminal offence without consent.
Environmental Permitting (England and Wales) Regulations 2016 (EPR) — discharging trade effluent to a watercourse requires either an EA environmental permit or a registered exemption under Schedule 2. Most mobile pressure washing operations do not have an EA permit.
Water Industry Act 1991 (WIA) — trade effluent discharged to the public sewer requires consent from the sewerage undertaker. Wash-down water from commercial cleaning is trade effluent. Discharge to sewer without consent is an offence.

What this means in practice for cleaning contractors

You cannot discharge wash-down water to a surface water drain without an EA permit — regardless of whether the water contains visible contamination.
You can discharge to a foul water drain if you have trade effluent consent from your sewerage undertaker.
You cannot assume washwater is harmless — detergents are toxic to aquatic invertebrates at very low concentrations. Biocides used in softwash are specifically designed to kill biological organisms.
Mobile cleaning contractors who work at different sites each day cannot control where their wash-down water goes at a customer's premises. Use containment matting or a recirculating collection system and remove collected water for licensed disposal.

The Groundwater Regulations

The Groundwater (England and Wales) Regulations 2009 prohibit direct or indirect discharge of listed hazardous substances to groundwater. Many cleaning biocides and degreasers are listed hazardous substances. On sites with no mains drainage, wash-down water running into permeable ground or a soakaway constitutes an indirect groundwater discharge and is a potential offence.

PFAS — emerging environmental liability

As PFAS restrictions tighten under the UK's 2026 PFAS Plan, wastewater containing fluorinated surfactants from cleaning products is an increasing environmental liability. Cleaning contractors using products containing PFAS should review their chemical procurement and drainage handling now. Further reading: PFAS in cleaning chemicals →

Practical controls for compliant pressure washing

Identify drainage type before starting — surface water or foul water? Ask the site manager if unsure. If surface water only, contain the runoff.
Use chemical injection sparingly — the more chemical used, the more significant the effluent. Check the SDS for biodegradability — biodegradable does not mean harmless to aquatic life at point of discharge.
Containment and collection — spill containment booms, collection sumps and water vacuum recovery are the most reliable controls for mobile operators.
Trade effluent consent — for fixed premises operations, obtain trade effluent consent from your sewerage undertaker.