JM wrote:
Hi,

I've just bought a house and tried to connect a washing machine today. The
plumbing includes valves a little like these (http://tinyurl.com/4lwpw) but
straight, not angled.

Unfortunately, there is some leaking, even if the taps are turned off and
the washing machine's hoses are connected (with the supplied filter
washers).

Is there leaking if the hoses are not actually connected, and the taps are
turned off?
If so, this is definately a fault.
In general, the rule for this sort of thing is to if, when it leaks a bit
on assembly, after you've tightened it up, open it up and examine the
seating surfaces of the washer/... for debris or flashing from the mould.
Smooth it flat, if it's not quite flat.
Then reassemble, and give it another tighten.
Grab the body of the valve in a pair of mole-grips or something, and
you can then really tighten the plastic bit.
Putting the plastic connector in boiling water for a couple of minutes
first can make it easier.