When the pressure washer helps and when it harms
The pressure washer is excellent for rinsing off loose dirt and on hard, durable surfaces. Problems start when you try to replace a cleaning product with high pressure or aim it at sensitive materials. Water under pressure neither dissolves grease nor removes algae as well as chemistry, but it easily damages delicate surfaces.
The best results come from combining two things. The product does the actual work, and the pressure washer on a moderate setting rinses off the dissolved dirt.
Pressure, nozzle, distance and angle
Four settings decide whether the washing is safe.
- Pressure. Start with lower pressure and increase only when the surface requires it and can safely take it.
- Nozzle. A wide jet is gentler, a narrow, pinpoint one concentrates all the force in one place and most easily damages the surface.
- Distance. The closer to the nozzle, the stronger the action. Keep a reasonable distance and reduce it carefully.
- Angle. Guide the jet at a reasonable angle, not straight down and pinpoint into a joint or edge.
Tip
Always start with gentler settings and a test in an inconspicuous spot. It is easier to increase the force than to undo damage to the surface.
Surfaces sensitive to pressure
- Thin coat render on the facade, which is easily damaged by high pressure.
- Wood, in which too strong a jet raises and frays the surface.
- Metal roof tiles and shingles, with a delicate coating and granules.
- Joints of pavers and masonry, from which water washes out sand and mortar.
- Old and brittle surfaces, which generally require care.
Washing safely step by step
- 1Remove loose dirt dry. Sweep away sand, leaves and loose dirt before you reach for water. Less loose dirt means less work for the washer.
- 2Apply the product if needed. For algae, grease and difficult dirt, act with chemistry first, according to its instructions.
- 3Set gentle parameters and do a test. Start with a wide nozzle, lower pressure and a reasonable distance, then check the result in an inconspicuous spot.
- 4Rinse evenly and with sense. Guide the jet evenly, usually from top to bottom, without holding the force in one point.
- 5Top up the joints after washing. If the water washed sand out of the pavers, top up the joints and let them dry.
Note
Never aim a narrow, pinpoint jet from close range straight into a joint, an edge or a delicate coating. This is the most common cause of permanent damage. When working at height, also remember the safety rules.
The most common mistakes with the pressure washer
- Replacing a cleaning product with pressure alone.
- Too high pressure on sensitive surfaces.
- A pinpoint, narrow jet from close range, aimed into joints and edges.
- Washing without first removing loose dirt.
- Forgetting to top up the joints after washing out the sand.
Frequently asked questions
Does a pressure washer replace a cleaning product?
No. Water under pressure rinses off loose dirt but does not dissolve grease or remove algae as well as chemistry. The best results come from a product combined with moderate rinsing.
What pressure is safe for pavers?
There is no single figure, because it depends on the state of the pavers and joints. It is safer to start with lower pressure, a wide nozzle and a reasonable distance, and increase the force only if needed and carefully.
Can I wash a facade and wood with a pressure washer?
Yes, but with great moderation. Thin coat render and wood are easily damaged by high pressure, so use gentle settings and do a test first.
Why is sand missing from the joints after the pressure washer?
Too strong a jet washes sand out of the paver joints. This is a common result of excessive pressure. After washing, top up the joints and let them dry.
