Quick answer: Car park and commercial hard standing cleaning is one of the most environmental compliance-sensitive pressure washing applications. Car parks accumulate hydrocarbons -- oil drips, fuel residue, brake dust -- that make wash water a potential pollutant requiring controlled discharge. Most car park and hard standing drains connect to surface water drainage and discharge directly to a watercourse -- discharging wash water to these drains without an EA permit is a criminal offence. This guide covers surface assessment, equipment selection, drainage identification, wash water containment and the correct method for block paving, tarmac and concrete car parks.
Car park cleaning contracts are a significant and growing market for commercial pressure washing contractors -- driven by facilities management frameworks, retail property management, local authority contracts and the increasing requirement on commercial property owners to maintain external appearance and comply with environmental obligations. But car park cleaning done incorrectly creates significant environmental liability for both the contractor and the client.
Step 1 -- Drainage identification before starting
The single most important step before beginning any car park cleaning is to identify where the drainage goes.
Car park and hard standing drains in the UK almost always connect to surface water drainage -- rainwater gullies that discharge directly to a local watercourse without treatment. This is normal and correct for rainwater. It is not acceptable for wash water containing hydrocarbons, detergents and suspended solids.
Before starting, walk the site and identify all drainage points. Ask the site facilities manager or property manager which drains are surface water and which (if any) are foul. On most commercial car parks, all drains will be surface water. This means wash water must be contained and collected, not washed into the drains. See: Environmental Permitting guidance
Step 2 -- Drain blocking and containment
Before beginning cleaning, block surface water drains using drain plugs or drain covers. This contains wash water on the surface so it can be collected by wet vacuum rather than flowing to the drain. Temporary containment berms around the work area prevent wash water spreading to areas where it might reach an unblocked drain or run off the edge of the hard standing into permeable ground.
A V-TUF MAMMOTH industrial wet vacuum is the practical tool for wash water recovery from a contained area -- the 80-litre stainless tank provides the capacity to collect significant volumes of wash water for removal from site by licensed waste carrier. See: View MAMMOTH 240V Stainless
Step 3 -- Surface assessment and equipment selection
Block paving
Block paving requires lower pressure than tarmac or concrete to avoid disturbing the jointing sand. 100-120 bar maximum, with a surface cleaner attachment rather than a direct lance for flat areas. Direct lance use on block paving scours jointing sand out of the joints and degrades the surface -- a common cause of complaints and callbacks. A rotary surface cleaner at controlled pressure provides even cleaning without jet damage.
Tarmac and asphalt
Tarmac can be cleaned at higher pressure -- 150-200 bar is effective for ingrained oil and tyre marks. Hot water is more effective than cold for removing hydrocarbon contamination from tarmac surfaces. A hot water pressure washer at 70-80 degrees C with a degreaser applied by downstream chemical injection reduces cleaning time significantly on heavily contaminated tarmac.
Concrete
Concrete car parks tolerate the highest pressure -- up to 250 bar on robust industrial concrete. Surface cleaner attachments are recommended for large flat areas to avoid striping. Oil stains on concrete benefit from a degreaser pre-treatment and dwell time before pressure washing.
Step 4 -- Collected water disposal
Wash water collected by wet vacuum must be removed from site and disposed of by a licensed waste carrier to an authorised facility. As the waste producer, the client is responsible for the waste transfer note -- but in practice, cleaning contractors who offer a complete service including licensed waste disposal are more competitive on commercial contracts than those who leave the waste for the client to manage.
CAZ and clean air zone considerations
For contractors operating vehicles and cleaning equipment in Clean Air Zone areas, vehicle compliance and equipment battery capability are operational considerations. See: Clean Air Zones, ULEZ and DVS
Related guidance
Environmental Permitting and trade effluent | Cleaning trade hub | Environmental Permitting article | View V-TUF pressure washers | Hot water pressure washers
