On 01/05/2011 18:25, Rick Hughes wrote:

"Ret." wrote in message
...
Rick Hughes wrote:
I have a KEW Hobby pressure washer ...... been great to date ... but
yesterday started surging.

This is significant enough to make it useless, almost equal cadence
between pressure & no pressure ... the outlet pressure gauge is also
reading nothing ... but that may be just a duff gauge.

Anybody any experience with pressure washers ?

No shortage of incoming mains (pressure or flow rate) even tried
different hoses & fittings to be 100% sure of that.

Try it without the lance. Do you get a steady stream of water?

If I operate lance without unit being switched on ... water is
jetting out OK.
Plus when it 'surges' it does seem right pressure and flow at the
peak of each surge.

I had a similar problem with a Karcher - and prodding some grit out of
the jet with the provided 'prodder' did the trick.


Changed lance to scrubber unit ... still the same, so not related to
hose or lance.

In that case it sounds like the by pass (or unloader) valve is out of
kilter.

To explain whats occurring; Say the working pressure is 100 bar. The by
pass valve is basically a piston held shut by a spring.

When the trigger is closed the back pressure rises to say 105 bar and
forces the valve open - allowing water to flow back into the inlet &
round in a continuous loop. When the gun is opened the pressure against
the spring drops allowing the valve to close.

A partial blockage in the nozzle would cause the back pressure to rise &
operate the valve, the pressure drops so the valve closes, the pressure
rises & the valve opens, etc etc etc.

If the valve is out of kilter (or the spring has broken) - e.g. set too
low - it causes exactly the symptoms you describe.

Page 5 part 60 here;

http://www.dolmar.nl/images/files/tekeningen/HP11.pdf

Spring pressure needs increasing 'very slightly'. Or a new valve.

p.s. Not using Hozelock 'Waterstop' connectors by any chance?


--
Dave - The Medway Handyman www.medwayhandyman.co.uk