Are there any snags to be expected if I replace some in-line valves? Are the
compression fitting threads always the same? (As the olives will prevent me
from changing them)
Is it always as simple as undoing the old fitting, removing it and
substituting it with new? The pipework is around 20 years old - 15mm.
(I don't want any snags as it involves working in a tight space.)
On 14 Dec,
The old ones will almost certainly have BSP threads. New ones of reputable
make usually are the same, but I've had some from B&Q in recent years with a
finer thread. Some heating components, Zone valves in particular can be
The threads should be the same but ...
... there's no standard for the amount of pipe which projects beyond the
olive to butt up against the valve body. No problem if the pipe projection
is a bit shorter than the available space but you won't be able to get the
olive to seat properly against the seat on valve body if the pipe projects
too far - BTDTGTTS. In that case you'll need to replace the olive, possible
1) Carefully make an axial cut in the olive with a junior hacksaw or Dremel
and spring it apart with a flat screwdriver blade.
2) Use an olive puller.
3) If the olive isn't too firmly attached to the pipe you may be able to
drive it off by placing an open ended spanner behind it and judiciously
hammering. This approach could damage the pipe and is not generally
recommended but it has worked for me in the past, perhaps I was just lucky.
We had a fair bit of discussion about this a couple of months ago, see
The only thing that usually varies is the amount of pipe that pokes into
the fitting beyond the olive. If you unlucky enough to have one that has
quite a long protrusion of pipe, you may find that it will not go far
enough into an alternative fitting to allow the olive to reach the body
of the valve and make a seal. The only solution then is to trim the very
end of the pipe with a hacksaw or remove the olive and use a new one.
John explained on 14/12/2007 :
Usually they will be, but why not think in terms of taking the old
olives off to replace the lot?
Often a good pair of large plier placed around the pipe, under the
olive then given a gentle tap will get the olive to move - unless it
has been over tightened. If it has been over tightened such that it has
dug into the pipe, you can usually get them off by sawing through most
of the olive with a junior, then forcing it to split with a sharp screw
Copper olives usually seal better with less pressure needed, but most
fittings supply brass with them.
from "John" contains these words:
As already mentioned some valves do have extra fine threads but there
has also been a change of thread on either 15mm or 22mm (or the inch
version as then was) some considerable time ago. I can't remember for
sure which it was but it was more likely to have been the larger size.
As long as you don't break anything or cut anything you can always refit
the original if you run into an unexpected problem.
I anticipate that the olives will be well embedded. Will be great if I can
get them off - I might even be able to cut the pipe near the olive if I have
to as there will be some 'adjustment' in the pipe - but prefer a simple -
"remove stop valve - replace with full bore isolator" whilst lying down in
the roof space.