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.)
Usually. If it would make the job very VERY awkward you can bet you'll get some non-standard ones :-(
"John Stumbles" wrote
Either that or the olives will be overtightened and refuse to seal to new fittings!
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 different too.
Get a tube of Fernox LS-X at the same time, it works wonders (usually).
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 methods are:
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
You can also cut off some of the projecting end of the pipe with a hacksaw.
Robert
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 driver.
Copper olives usually seal better with less pressure needed, but most fittings supply brass with them.
The message 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.
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