Why shouldn’t you use one ? Does it cause an issue?
I have one on mine on he end that connects to the pressure washer, have had it fitted for years no issues.


Rob. 2011 (MY12) 4.4 TDV8 Vogue
2016 Golf GTI PP

Gone
Audi A4
VW Passat
VW Corrado G60
VW Golf GTI
BMW E30
Mini
Vauxhall Chvette

The missus opened the tap and the pressure started to cause an ankle bashing motion like a demented snake. Not good if the dog or a child is in the way. 2018 SE SDV8 4.4 Byron Blue

Rob, I’ve killed two kaerchers that way with leaky motors. Got to say Nilfisk didn’t have such issues but had others. I think the issue is the back pressure when letting go of the trigger and it has nowhere to go. Putting additional strain then on the pressure washer motor and seals. Nearly all my hozelock connectors all had a non return valve. So this time for my K7 I got the kaercher connection kit and wouldn’t you know. It includes a hozelock style connector with aqua stop but without a non return valve. The machine is very smooth indeed. Hopefully I now have many years of pleasure from it.

Hmm,May need to look at it then. Don’t use it very often so may not be apparent for a while.

Rob. 2011 (MY12) 4.4 TDV8 Vogue
2016 Golf GTI PP

Gone
Audi A4
VW Passat
VW Corrado G60
VW Golf GTI
BMW E30
Mini
Vauxhall Chvette

Yeah got one of dem too! OK for two years then it started spraying you at the variant spray nozzle end - possibly as we leave it in an old plasticky rubbery bin outside the shed in ALL weathers. I guess the frost has gotten to it... the hose is still OK though with little seepage. Might try putting some clear silicone all around the spray gun join/s seam/s to eke another few years of use from it.