Compression joints

Jerry_N

OK all you plumbers out there. Following a major leak the section of work surface into which our kitchen sinks sits had to be replaced. That necessitated the removal of our monobloc tap unit which required the undoing of the relevant flexi pipes from two elbow compression joints. Once the work surface had been replaced the tap was reinstalled with the flexi pipes being reconnected to the elbow joints. After a few weeks we noticed some water on the shelf within the under sink unit. Having watched the connections I noticed a tiny droplet of water start to build up at the bottom of the hot feed elbow joint. After around 5 to 6 minutes the droplet then fell onto the sink unit shelf.

Now to cut a long story short, an "expert" sent by our insurers has said that, in his experience, when the connection at one end of a compression fitting is undone the connection at the other end will NEVER loosen up! Also that same expert has said that, where PTF tape is used to act as a seal on a compression fitting, the tape will degrade thereby causing a leak.

So plumbers, is he correct? is it true that the undoing of the connection at one end of a compression fitting will NEVER lead to the connection at the other end loosening up - even very slightly - and will ptf tape degrade over time which, in our case, is less than 3 & a half years after the relevant compression fitting was initially installed/

Alex1983

Ptfe tape has no place on a compression fitting, the olive is the seal. If you loosen a compression in will not make the other end impossible to undo.

I would think either it needs tightening up, the olive is not fully on or the pipe is out of shape.

Strider590

The way compression fitting should be done is no PTFE tape and only the olive to seal.....
However IF the pipe is old and had to be cleaned up with say silicon carbide paper (wet n dry), then you'd use jointing compound (Boss white being the most well known) to ensure a good seal.

Grenage

Yes, PTFE tape on compression fittings is the mark of a bodger.

nofoollikeold

1. It is possible for the "other end" of a compression fitting to loosen while undoing the other end or indeed when tightening it up again. However, its fairly unusual, and very unusual on an elbow.
2. I do this for a living, and am quite happy to use PTFE tape around the olive(s) on an old compression fitting once disturbed. Three or four wraps around the olive does help to guard against leaks, and I've never know it degrade. New pipes and fittings don't require anything on the olive provided they are decent quality. If I have to use cheap fittings I use Jet Blue paste both sides of each olive.
3. I assume from the original post that it the end of the elbow connected to solid pipe which is leaking because of the mention of "other end loosening". It is often quite difficult to determine the exact point a leak is coming from, and I wouldn't be surprised if its coming from where the flexible hose has been reconnected. Flexible hoses with 1/2" or 3/8" BSP female ends should not be connected directly to compression fittings, which have a sharp edge which can damage the seal inside the nut at the end of the hose. A short piece of pipe and 15mm / 1/2" (or other size as appropriate) "iron" or a special fitting should interpose.

Rodders53

Flexis into a monobloc tap should not loosen when the other end is disturbed, but might if they weren't fully tightened originally where they screw into the monobloc. The act of tightening the compression nuts can cause the flex to twist, which may loosen the already loose tap joint further... but any competent plumber would know and allow for this. (Probably nipping up both joints before re-fixing tap to sink/work surface).

What is the real issue here? You have a leak following work done. Original plumber ought to want to correct and fix it?

Jerry_N

Can any of you plumbers out there tell me a buckled olive is?

Carrot007

Jerry_N wrote: »

Can any of you plumbers out there tell me a buckled olive is?

It's an olive which is out of shape so will leak.

Probably because it has been re-used. Never re-use an olive!

BazMan23_2

Yeah you should NEVER use tape or dope with compression tube fittings. In short, because tube fittings seal on the FERRULE (olive) and not the THREADS, pipe tape or dope can stop the nut from screwing down far enough to create the seal or stray pieces of tape can get stuck on the ferrule (olive) and interrupt the seal. Don't trust a plumber who uses pipe tape and compression fittings lol. I found an article about tape and compression fittings on Titan Fittings but I can't find it right now. I'll edit later if i find it.