RogerBW's Blog

Karcher K7 Pressure Washer 03 August 2017

I never felt a need for a pressure washer before I moved here; but we have substantial areas of paved outdoor space, and they need to be kept clear of weeds and general grot.

I've used cheapies sold via Lidl (with brand names like "Powerbase"), and they're not too bad for occasionl use. The most recent one has a 1400W air-cooled motor and an operating pressure of 65 bar (6.5 MPa), as well as a 3m high-pressure hose. That's OK, just about, but repeatedly moving the thing about is hard work, and it's really not up to extended use. The area in which much cheap equipment falls down is cooling, because if you're only going to use it for a few minutes at a time you don't need to worry about overheating.

But it really wasn't up to the job of getting weeds out of a resin-bonded drive, and rather than mess about with half measures I got the K7. (Strictly a "K7 Premium Full Control Plus Home", which might mean something to someone.) Kärcher (branded as Karcher in the UK) makes cleaning equipment ranging from small units like this to massive industrial stuff.

The motor power goes up to 1800W, but more importantly it's water-cooled, so it can run for half an hour or more without getting any overheating problems. The high-pressure hose is 10m long, so I can put the machine down in one spot and do the entire drive. Operating pressure is 180 bar, which is the really important difference: this will casually remove weed growth that the old machine wouldn't touch.

There's rather more attention to detail: the case is still plastic, but it's slightly more solid plastic without metal housings peeking out, and it has wheels and a telescoping handle to make it easier to move around. There's a built-in reel for the high-pressure hose (though not for the mains cable, alas). The main nozzle unit has the two basic modes that the Powerbase unit offers (a flat divergent-angled spray, or an eccentric jet falling in a conical pattern), but you can select them just by turning the end piece rather than replacing hardware, and it adds a shampoo mixing mode; power level is controlled by a short-range radio sender in the handgrip. (Which is why this mains-powered device also needs batteries.) This is quite handy: for example, I was washing down the front steps, and could quickly drop to a lower power mode to wash the front of the house clean of all the débris that had been kicked up, then return at once to the main job.

The package comes with a "T-Racer" patio cleaner, which I haven't yet used (apparently it's vulnerable to damage from loose stones), but more importantly includes an extension piece for the nozzle unit, so one doesn't have to be constantly bending to reach the ground with a close-up spray.

Shampoo, of course, comes in specially-shaped Kärcher bottles. Even Kärcher sell their own-brand detergent in larger bottles for topping up these small ones, so it's clear they're not as serious about profiteering by preventing refills as a British or American company might be. (The firm is still family-owned.) And I imagine one could 3d-print an adaptor piece for other bottle shapes without too much trouble.

Ear, eye and hand protection are recommended. I don't bother with the last of these, but it's certainly a bit louder than the old machine, and my goggles have taken a couple of hits from small bits of débris. (I'm still getting used to having to protect my eyes again, having worn glasses from about age ten until a couple of years ago.)

This is a jolly expensive piece of kit, but it gets the job done in a way which the cheap unit never did.

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Tags: toys

  1. Posted by Owen Smith at 09:43am on 03 August 2017

    I bought my mum a decent Karcher pressure washer a few years ago. Like yours it crucially is water cooled (motor and bearings) so use for an hour or more is no problem, and 1800W motor rings a bell as does the 10m pressure hose. I think it has an induction motor, it's only just loud enough to need ear protection to use it, my parents tend not to bother with the ear protection being half deaf already due to age.

    So yes I'd agree that with pressure washers, it pays to buy a good model. I'd say the water cooling is the most crucial feature.

  2. Posted by John Dallman at 08:22pm on 03 August 2017

    Well, that would be one way to get the weeds out of my driveway. How does tarmac stand up to something like this?

  3. Posted by RogerBW at 09:21pm on 03 August 2017

    Pretty well, in general. You'd be welcome to borrow it, with or without me to drive it.

  4. Posted by John Dallman at 06:58pm on 04 August 2017

    Please bring it over some time and I'll give it a try. No hurry.

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