On 13/11/2017 07:55, sweetheart wrote:

I have just bought my husband a Karcher K4 complete control pressure
washer to replace his 20 year old defunct one which gave up the
ghost. . It was supposed to be for Christmas but it arrived and he
saw it!

I got the K4 because I thought it was the better one - reading
reviews. Now OH tells me it cannot be used on a mains supply because
it is too powerful. Is this true?

Not because it is too powerful but because the water companies don't
like you connecting things that can potentially pump chemicals back into
their drinking water supply network if things go wrong.

I didnt get it to use on a ruddy water butt. I intended it to link
into the outside tap where we currently have the hosepipes
connected.

Why do none of the review sites or even the information about the K$
state it cannot be used on domestic supplies? OH read it in the
instructions ( yes it does say " cannot be used on the water net") .
So, can it be used or not?

I think you will find it actually means that you should have a
non-return valve in the path to the tap (and that will have been true of
your previous one too). It is to protect the mains water supply from
blowback of industrial detergent into the supply.

https://www.amazon.co.uk/Hozelock-No...dp/B005A5LZBI/

There are cheaper ones - this was the first I found online.
Mine is a Hozelock.

--
Regards,
Martin Brown