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.
If I operate lance without unit being switched on ... water is jetting out
Plus when it 'surges' it does seem right pressure and flow at the peak of
At what rate is it surging - like several times per second, once every
few seconds, etc.?
During this pressure fluctuation, is the motor running all the time - or
does it keep starting and stopping?
When you fist turn it on with the outlet closed (i.e. trigger on lance
not operated) does get up to pressure and then cut the motor, like it's
[Anyone know how many pistons a typical pressure washer has in its pump,
and what the rotational speed is likely to be?]
That would tie in with the in-use sound ..you can hear pump getting up to
pressure, and if you are 'jetting' it is one, sound, when you release the
trigger, sound changes as I presume it reaches peak pressure and 'by pass'
opens ... but certainly does not stop running.
Try it without the lance. Do you get a steady stream of water?
In that case it sounds like the by pass (or unloader) valve is out of
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;
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
Great explanation .,.. I am away for a few days with work ... will take a
look, maybe a clean will fix :-)
Don't suppose you have same parts list / drawings for the Hobby 88 ?
It is a rectangular box type, rather than upright.
On Sun, 01 May 2011 20:47:52 +0100, The Medway Handyman wrote:
Just read through the thread, I still have a very old KEW Hobby, bought at
the Ideal Homes Exhibition many many years ago. I also had this problem,
and in the end it turned out to be using waterstop connectors on the inlet.
Also had trouble with grit in the lance, had to buy a new lance, as the old
one didn't lend itself to my style of DIY disassembly! :-)
Still in the garage unused now as it was bl**dy heavy to lug around, now
replaced with a Nilfisk.
An expert is someone who has made all the mistakes
On Thu, 5 May 2011 20:12:23 +0100, The Wanderer wrote:
I can't work out why waterstop connectors are supposed to be a
problem or if they are how. When connected the male spigot physicaly
pushes the valve open, no way can it be sucked shut.
Maybe some people put waterstops at both ends of the hose and the one
at the tap end is sucked too far open blocking the flow? Easy cure
On Thu, 05 May 2011 22:26:23 +0100 (BST), Dave Liquorice wrote:
On the face of it, I've got to agree with you, there shouldn't be a
problem. Except that from personal experience I can say there is! I can
only think that the whole arrangement (the spigot, the rubber seal, the
actual clearance when open) restricts the flow into the pump.
nope ... I took lance off and fitted a patio scrubbere - exactly the same
surging, so not nozzle related.
I also have a separate nozzle (rotating) tried that ... same surging.
nozzle pressure 88 bar
most other specs are about hose size & dimensions etc.
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