Karcher K4 Premium High Pressure washer review

Want to know what makes a truly great pressure washer? A pressure washer is a power tool that directs water at high pressure to clean garden and other external surfaces of your property. It connects to your household water tap and needs to be plugged to a household electricity power point. 

One of the best pressure washers is the perfect tool for tackling various areas that can be prone to the consequences of the weather, including stone patios, wooden decks, windows, brick walls and facades. These tend to accumulate mildew, and gather stains or get slippery underfoot. This tool allows you to keep on top of the maintenance of your home so that it's spick and span year round. 

I hadn’t owned a pressure washer before so when I was researching garden upkeep, this appliance seemed to tick all the boxes. I have a small back garden that instead of grass has various stone patios and steps, plus wooden decks and pathways. All of which need annual maintenance. I wanted a product that could tackle the basics with rigour and energy. My mantra when buying electrical products is ‘to buy once and buy well’. I want things to last so that I am doing my bit for environmental sustainability. 

It was a gloomy day at the beginning of Spring when I put the Karcher through its paces…

Karcher K4 Premium High Pressure Washer product specs

• Power type: 1800w
• Max pressure: 20-130 bar max
• Best for: Stone outdoor surfaces and cars
• Hose length: 5m
• Power cord length: 5m
• Net Weight without accessories: 11.48 kg

Who tested this pressure washer? 

Rhoda Parry

Rhoda Parry is the former Editorial Director of Ideal Home, the UK’s best-known media brand, and its sister titles, 25 Beautiful Homes and Style at Home. She is also former Editorial Director for Gardeningetc, Amateur Gardening and Easy Gardens. 

As an experienced Interiors and Gardens journalist, she’s spent her career tracking the trends, interviewing the experts and reviewing the best products for inside and outside living spaces. 

Karcher K4 Premium High Pressure Washer: Unboxing and delivery

The Karcher K4 arrived efficiently and well packaged in a large signature Karcher yellow box. The box was supported by two plastic ties around the middle for strength and lifting but there were no side handles on the box that may have made it easier to man handle. The package was heavy and I couldn't lift it single handedly so I needed a helpful hand from my other half to get it into the house.

The packaging was made of good quality, heavy duty cardboard, which we all know is widely recycled, but there was no recycle logo confirming this on the packaging. It was printed with the name of the product and clearly pictured what was waiting inside  – the K4 kit, Home Kit and Car kit – and the pressure washer’s vital statistics, such as power type, water flower rate and area efficiency. This looked like a serious product that knew what it was talking about and I couldn't wait to see how it performed. 

Karcher K4 Premium High Pressure Washer: First impressions 

On opening the box, all the contents were neatly arranged and held in place by more cardboard. A yellow strip commands you to ‘Scan your product code and get your benefits’. This involves downloading the Karcher Home & Garden app from the Apple App Store or Google Play. Then opening the app, selecting Higher Pressure Washer and then scanning the Product Code. I was slightly unnerved by the fact that I have to do this in order to ‘control the device’ but I dutifully followed the instructions to register and set up an account with Karcher. Paper instructions are included for those who don’t own a smartphone.

I moved outside at this point to lay out all the components before putting the pressure washer together. All the items are pretty obvious. You do need your own Phillips screwdriver to assemble certain parts. The app takes you through the process step by step to attach the wheels, base, gun and spray gun holders, two panels, and storage net. Then you screw the adaptor to the water connection. It's a good tip to completely unroll the hose so that it is untangled. 

Finally you insert the high pressure hose into the high pressure gun and fit the spray lance with a half rotation. After about 20 minutes of construction, the pressure washer is ready for action.

Performance 

Wooden sleeper pathway

I decided to start testing on the oak sleeper pathway. The wood was blackened and slippy after the cold and wet winter weather. Using the app, I clicked on Wooden Floors and it showed me that I needed to select Pressure level 1 Soft, the Nozzle setting and that there were 8 steps to cleaning wooden surfaces.

Firstly, I removed the loose dirt with a dustpan and brush, then I connected the Vario Power spray lance to the high-pressure gun, and set the pressure range to Soft. I guided the flat stream of water slowly, as per the instructions, in the direction of the grain - at the recommended angle of 30-50 degrees and about 12cm from the surface of the wooden surface. 

The soft setting gently cleaned the wood. Where it wasn’t powerful enough to remove ingrained plant debris I increased the pressure which allowed for better dispersion of soil, plant matter and algae.

Stone patio

Next I tackled the paved stone patio. Again, after the winter, the surface wasn’t looking its best with blackened patches and significant moss growing in the cracks between the pavers. I gave it a quick brush to remove pebbles and leaves.

Clicking on the app for instruction on Stone Floors, it suggested I use the T5 T-Racer Surface Cleaner, that the Pressure Level should be set to 3 Hard and to use the Nozzle setting. I easily connected the T5 T-Racer attachment and selected the Hard position. On usage, this attachment looks and feels a bit like an upright vacuum cleaner or sanding machine.

Due to the dome design, the water pressure is directed downwards and therefore doesn't spray up all over the place. It easily cleared the moss from the cracks and the dirt from the surface of the pavers. It’s a good idea to work in a methodical way in order to avoid missing patches. On the edges of the patio, I decided to use the spray lance on pressure range 3 high as I could direct the flow of water more easily. While the patio was wet, I gave it another quick brush and then gave it a final rise on pressure range 2 medium.

The kit is supplied with a Stone Cleaner that is inserted into the Plus ‘n’ Clean docking station. By selecting Mix on the spray lance the detergent is sprayed onto the stone and can then be rinsed off - quite useful if you have a particularly stained patio area.

Car

My car - which rarely gets cleaned - got the once over next. The app recommends that you brush any leaves before starting so that the run-off remains clear. The Vario Power spray was attached to the high pressure gun and set to pressure range 2 medium. I gave the car a quick once over with the spray jet to take off large lumps of mud. I live on a country track so we get a lot of mud! The instructions suggested to work from the bottom up, which is a useful tip.

Once that was done, I placed the Car Shampoo 3 in 1, which is supplied, into the Plug ‘n’ Clean docking station and turned the Vario Power lance to detergent mode or Mix as it was called on the trigger display. Working from bottom to top, I sprayed the car with the detergent and then left for a few minutes, as suggested, to let the suds do their magic. 

Then I grabbed the rotating brush attachment and rubbed the car down. Finally, with the Vario Power spray lance set to medium, I rinsed the car using the flat jet - again working from the bottom upwards. This was very much the method I’ve seen being used in car washing drive-ins and it worked brilliantly. I have a soft top car so I was a bit nervous about using the jet on the cloth roof so I set it to soft and it got rid of most of the moss and algae that had accumulated. 

Glass patio doors

We have large sliding doors that lead from the kitchen to the garden so using the Medium setting I gave them a quick rise. It was especially useful getting into the runners and sills where dirt accumulates over the winter months. Obviously, you do need to finish off a hand-held window cleaning wiper to avoid smears.

Other alternatives 

The instructions say you can use this product on stone walls and facades using the stone and facade cleaner, as well as motorbikes and bicycles. I didn’t test it on these areas but based on the above I think it would do a good job.

Final verdict: Is the Karcher K4 Premium High Pressure Washer worth the money? 

The Karcher K4 Premium High Pressure Washer really pulled its rank in tackling all the jobs I set it. It was very competent in removing dirt and grime on any given surface. It's a powerful machine and the three pressure settings mean you select the right pressure for the right job. The trigger handle display clearly shows the setting you are on.

In terms of user friendliness, it was easy to understand the instructions and, being a beginner, I found the app useful for its clear step by step instructions. The cable tidy handily reels in the cable for stowing in the garage or shed. The sturdy wheels and telescopic transporting handle make it easy to move the pressure washer from place to place as lifting the machine is heavy. The trigger is light and easy to handle.

The RRP is £399.99, which is a hefty investment, but if you need to clean patios, decks and pathways on a yearly basis I think it is worth the dosh. And, of course, if you are regularly spending £10 on getting your car cleaned at the garage drive-in every Sunday then this is going to save you money in the long term. It is also fun to use as there is something rather satisfying about the instant transformation to your outdoor surfaces, but also good safety wise as avoiding slippy outdoor surfaces is an imperative with kids about. My only con is how heavy it is!

About this review, and the reviewer

Rhoda tested the K4 Premium High Pressure Washer at her family house in Sussex where she put it through its paces on stone patios, wooden sleeper paths, windows and finally turned to cleaning her mud-covered car.