Glad I found this thread, been looking for a PW that'll use water from a water butt instead of a tap.
AvE's reviews are less about "does it work at least once on camera" (as you found, there are a bajillion other reviews that do that) but "will it last for a million years without maintenance, or will it make it half a turn, fart, and let the smoke out"? i.e. a focus on build quality rather than peak performance.
So, this might sound like a stupid question, but that's only 'cos it is (and DuckDuckGo's just shrugging its wings at me.) I've got a Hozelock hosepipe, which has two female QC/QD connectors at either end. One goes onto a male QC/QD on the bathroom tap and makes water happen; the other sits at the far end of the hose and a spray nozzle thingy clicks into it. Both male QC/QDs - the one on the tap and the one on the nozzle thingy - look a heck of a lot like the water input QC/QD on the Karcher (and the Worx, for that matter.) So... is it as simple as hooking my existing hose up to the tap, unplugging the spray nozzle, and connecting the hose to the water intake on the pressure washer? No additional adapters or special hoses required? My gut says the answer is "yes," but that sounds altogether too easy.
It definitely is that easy on the K2 I had, and says much the same in the k4 manual. I've also not seen special hose-pw adaptors anywhere.
Well, that simplifies things. Save up a bit more, get the Karcher, snow-blower thingy, bottle of snow, job's a good 'un. No need for the self-priming use-any-water-source add-on.
Pulled the trigger (no pun intended) on a K4 Full Control (brand new, as I figured the extra £40 wasn't too bad to go from a six-month to a three-year warranty and get the second lance thrown in), foamy foamer thing, litre bottle of the recommended foamy foam to try (on top of the litre of cherry flavour foam the foamy foamer thing comes with), a bottle of Karcher's own car shampoo ('cos it fits inside the washer and mixes automatically, and I can fill it with cheaper shampoo when it's emptied if I fancy), and an RCD ('cos obviously.) So, assuming I usually pay £5 to get the thing cleaned - whether at a hand wash, robo-wash, or using the pay-as-you-go pressure washers at the local garage - it should only take me... 40 washes to break even. Well, more, 'cos I doubt the bottles of goo are going to last 40 washes... Thanks for your help, all!