Commercial jet washing guide
Can You Jet Wash Tarmac?
Yes, but tarmac is one of the most commonly damaged surfaces from jet washing because the default settings on most machines are far too aggressive for it. This guide explains the specific pressure limits, nozzle requirements and detergent rules that make the difference between a clean tarmac surface and a ruined one.
Tarmac, also known as asphalt or bituminous macadam, is a composite material made from crushed stone aggregate bound together with bitumen, a petroleum-derived adhesive substance. This composition makes it robust under traffic loading but meaningfully more vulnerable to high-pressure water than concrete or block paving. The bitumen binder that holds the aggregate together softens under heat and is partially susceptible to damage from high-pressure impact when the surface is already warm from sun exposure. Using the standard lance on a domestic or commercial pressure washer at full pressure on a tarmac surface, particularly in summer, can dislodge aggregate particles, strip away the protective top layer and leave streak marks and pitted areas that are expensive to repair. The good news is that jet washing tarmac safely is entirely achievable with the right settings and approach.
1,200 to 1,800
PSI maximum for safe jet washing of tarmac. Above this risks dislodging aggregate, particularly on older or weathered surfaces
No hot water
hot water softens the bitumen binder in tarmac. Always use cold water when jet washing tarmac surfaces
Never a pencil jet
a 0-degree turbo nozzle on tarmac will cut into the surface instantly and cause irreversible damage in seconds
Understanding What Makes Tarmac Vulnerable To Jet Washing Damage
Concrete cures into a single hard monolithic surface where the aggregate particles are locked into a solid cement matrix. Pressure washing on concrete is working against a hard unified surface. Tarmac is different because the aggregate particles are bonded by bitumen, which is semi-flexible rather than rigid. The bitumen layer that coats each aggregate particle and fills the voids between particles is what gives tarmac its weather resistance and flexibility. High-pressure water impacts this surface differently to concrete: rather than simply removing dirt from a hard surface, it can find voids in the bitumen matrix and begin to dislodge particles. This effect is worst at the top of the surface where the bitumen layer is thinnest after weathering, and on older or trafficked tarmac where the surface has begun to oxidise. In hot weather or on tarmac that has been heated by sun exposure, the risk is significantly increased because the bitumen softens above approximately 30 to 40 degrees Celsius.
How to jet wash tarmac safelyThe Correct Method For Cleaning Tarmac With A Jet Washer
1. Time the clean correctly
Do not jet wash tarmac during hot sunny weather or when the surface temperature is elevated. Early morning or overcast days produce the best results. Wait until the surface has cooled fully after direct sun exposure before beginning any cleaning.
2. Pre-treat oil and grease stains with a tarmac-safe degreaser
Oil and diesel contamination on tarmac cannot be removed by pressure alone. Apply a degreaser specifically formulated for tarmac surfaces, not a concrete degreaser which may contain solvents that attack bitumen. Allow the product to dwell for 10 to 15 minutes before washing. This pre-treatment step is essential for any surface with fuel or oil contamination.
3. Set pressure to 1,200 to 1,800 PSI maximum with cold water only
Use only cold water as hot water softens bitumen and dramatically increases the risk of surface damage. Set the machine to the lower end of this range for older, weathered or degraded tarmac and increase only if the surface is clearly newer and in good condition.
4. Use a wide fan nozzle (40 degree) or surface cleaner attachment only
Never use a turbo or pencil jet nozzle on tarmac. Use a 40-degree wide fan nozzle held at a minimum 30 to 40 cm from the surface. A surface cleaner attachment is the best option for large tarmac areas as it distributes pressure evenly and eliminates the stripe marks that a lance produces on softer surfaces.
5. Keep moving at all times
Never hold the jet in one position on tarmac. Concentrated pressure in a single spot will damage the surface even at an otherwise acceptable pressure setting. Use smooth, overlapping sweeping passes and maintain a consistent distance throughout.
6. Seal after cleaning for longer-lasting results
Applying a tarmac sealant or restorer after cleaning replenishes the surface with a fresh protective layer, restores the dark colour of cleaned tarmac, reduces future staining penetration and extends the interval before the next professional clean is needed.
Things That Will Damage Tarmac During Jet Washing
The primary causes of tarmac damage from jet washing are: pressure above 2,000 PSI, particularly on older or sun-degraded surfaces; hot water, which softens the bitumen binder; turbo or zero-degree nozzles, which concentrate force into a pencil jet; concrete degreasers containing petroleum solvents, which attack bitumen; and holding the nozzle stationary on one area. Stripe marks are the most common consequence of incorrect nozzle or pressure choice and are difficult to disguise without resurfacing or sealing the entire area. Any cracked or potholed areas of tarmac should be repaired before jet washing because high-pressure water in existing cracks accelerates further deterioration of the sub-base.
Commercial jet washing London
Professional tarmac cleaning across London by Cloud Nine
Cloud Nine cleans tarmac car parks, forecourts and service roads across London using cold water at the correct pressure setting with tarmac-safe degreasers. We never use hot water or high-pressure lances on tarmac. Contact us for a free quote.
Part of our guide
Commercial Jet Washing Help And Guidance
Everything London businesses need to know about commercial jet washing.
Back to the guide