A pressure washer is easy to use, but it is also powerful. Most of the damage we see on patios, cars and facades is not down to a bad machine, but to a few common mistakes. These are the ones that come up most often and how to avoid them.
1. The wrong nozzle for the surface
The rotary nozzle (Dirt Blaster) is for concrete, stone and stubborn dirt. On wood, car paint, tyres and render it causes damage. For delicate surfaces, use the Vario Power lance with a flat jet.
2. Too little distance
The closer the nozzle, the stronger the jet. Always start at least 30 to 50 cm away and move closer gradually, on a hidden part of the surface. Never hold the jet on one spot for long.
3. Too much pressure "just in case"
The highest pressure is not always the best. On wood, joints and facades, high pressure tears up fibres, washes out joints and strips render. Start with a lower setting on the Vario Power lance and only increase it as much as needed.
4. Running without enough water
The machine must be connected to water with the tap fully open before you switch it on. Running without water or with too little water damages the pump. The garden hose must not be kinked or too narrow, and the water going into the K 7 can be at most 60 °C.
5. Household products in the machine
Do not put washing-up liquid, vinegar, bleach or similar products in the machine or the Plug 'n' Clean container. They can damage the seals and pump, and some are harmful to the environment. Only use products made for pressure washers.
6. Aiming the jet at electrics, people and animals
Never point the jet at sockets, cables, lights, the machine itself, people or animals. High pressure can injure skin and eyes. Keep children and pets away while you work.
7. An extension cable used the wrong way
If you use an extension cable, it should be rated for outdoor use, have the cross-section given in the instructions and be fully unwound. Keep the cable connection out of the water, somewhere dry and raised.
8. Working on ladders and roofs
The jet has a kickback that can throw you off balance. Do not work from a ladder and do not climb onto a roof with a pressure washer. Old fibre cement roofs and cladding may contain asbestos and must never be pressure washed.
9. Washing in hot sun or frost
In strong sun, products and water dry before you can rinse them and leave marks. In frost, water stays in pores and joints and, when it freezes, damages stone, concrete and the machine itself. Wash in mild, dry weather.
10. Leaving the machine under pressure or in the cold
After work, turn off the water, release the pressure from the gun, switch the machine off and coil the hose without kinks. Keep a home pressure washer somewhere frost-free, as water left inside can damage the pump. If the machine is hired, all of this applies until you return it.
For specific jobs, see our guides: cleaning a patio, washing a car and facades, fences and garden furniture.
Frequently asked questions
Why does the pressure washer pulse or switch itself on and off?
Usually because there is not enough water coming in: the tap is not fully open, the hose is kinked or the inlet filter is blocked. Check the water supply, and if the problem continues, switch the machine off.
Why is the jet weaker than usual?
The nozzle may be partly blocked, the machine may not be getting enough water, or the Vario Power lance may be on a low setting. Check the water supply, the lance setting and whether the nozzle is clean, in that order.
Can I leave the machine running without pressing the trigger?
Home machines stop by themselves when you release the trigger, but do not leave the machine switched on for a long time without working. Switch it off when you take a break.
Can I use a longer garden hose?
Yes, if it supplies the machine with enough water. A hose that is too long or too narrow reduces the flow, so the machine does not work properly. Keep the hose straight, without knots or kinks.
Does the machine need cleaning after use?
If you used a cleaning product, briefly rinse the system with clean water at the end. Wipe the nozzles and attachments, and check and clean the water inlet filter now and then.
Can a pressure washer damage the grout between tiles?
It can, if you aim the jet straight into the joint from close range. Wash at an angle, from further away and at lower pressure, and top up washed-out sand between pavers once dry.
Is a pressure washer dangerous for children and pets?
A high-pressure jet can injure skin and eyes, so children and pets should keep a safe distance while you work. Afterwards, put the gun away where children cannot reach it.
Do I need safety glasses?
We recommend them. The jet throws up small stones, sand and dirt that can hit your eyes. Non-slip shoes are useful too.
Can I wash a lawnmower or garden machinery with a pressure washer?
You can clean the housing and cutting parts, but without aiming the jet at the engine, air filter, bearings or electrical parts. For electric or battery mowers, follow the manufacturer's instructions.
What if I am not sure whether something can be pressure washed?
Try the lowest pressure from a large distance on a hidden part. If you see any change in the surface, stop. For expensive and delicate surfaces, check the manufacturer's instructions or feel free to call us.
Want to work with a powerful machine in good order? Hire a Kärcher K 7 from us, with operating instructions and delivery by arrangement.
