Pressure washer
Mechanical energy delivered by water alone. It removes what nothing else will and takes the surface with it more often than any other domestic tool.
What not to do
Pressure washer should be avoided for Concrete and stone paving
Best avoided
The available guidance advises against this.
Permitted within the manufacturer's stated limits. Outside them it removes jointing material and marks the surface.
Precautions
- Test on an inconspicuous area first
- Check the manufacturer's instructions
Evidence
Supported
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That power washing used to excess damages the paving and shortens its service life, that the lance must not be directed down onto the paving because that costs jointing material, and that some machines mark wet cast paving. (states this directly)
Pressure washer should be avoided for Garden ornament
Best avoided
The available guidance advises against this.
Precautions
- Test on an inconspicuous area first
- Wear eye protection
Evidence
Supported
Sources
Conserve O Gram 15/2: Dusting Guidelines for Stone Objects and Interior Architectural Features
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That soft stones such as marble, limestone, alabaster and soapstone can be easily scratched by improper procedures and that highly porous stones entrap dust. (states this directly)
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That power washing used to excess damages a surface and shortens its service life. (states this directly)
Pressure washer should be avoided for Bicycle
Best avoided
The available guidance advises against this.
The bicycle tool maker's limit is a hose at LOW pressure with a WIDE spray, and compressed air is never blasted at the bearings. A pressure washer is the opposite of both.
Evidence
Supported
Sources
Park Tool Co. · Manufacturer documentation
Relied on for: That a hose is used only at low pressure with a wide spray, that compressed air must not be blasted directly at bearings, and that keeping solvent out of the bearings is an explicit aim. (inferred from the source; not stated directly)
Precautions
- Wear eye protection
- Check the manufacturer's instructions
- Test on an inconspicuous area first
- Keep away from children and pets
In detail
A pressure washer cleans by kinetic energy: water accelerated through a small orifice strips loose material off a hard surface without any chemistry at all. Outdoors on concrete, brick, render and durable paving it does in minutes what a brush cannot do in an afternoon. The problem is that the energy does not distinguish between the deposit and the substrate. On paving it erodes the jointing sand and the mortar first, which is what leads to weeds and movement the following season; on soft stone, aged brick and lime mortar it removes the weathered face; on timber it raises the grain and tears the softer summer wood out between the harder growth rings; on render and on painted surfaces it strips the coating. Manufacturers of paving products consequently specify pressure limits, fan nozzles rather than pencil jets, and a working distance. Two further considerations are usually overlooked. Water driven under pressure goes where poured water does not — under cladding, into airbricks, past window seals and into electrical fittings. And the spray aerosolises whatever it hits, which matters when the surface carries algae, bird droppings or moss.
Sources for this page
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That the manufacturer specifies limits on pressure washing paving, including nozzle type and working distance, because of damage to the surface and to the jointing. (states this directly)