Compression fittings

[Dippy]

I have just finished a DIY plumbing job. I did a bit of solder ring & push-fit plumbing recently when I had to change a monobloc kitchen tap with different tails, but it has been over 10 years since I used any compression fittings. Also back then I was only using 15mm.

This job I needed to do both 15mm and 22mm. For a number of reasons compression seemed to me to be the best solution. I bought fittings from TS and Wickes (they look the same anyway) and did a bit of forum reading which seemed to advise that I either use nothing or a bit of Boss or similar on the olives before tightening. I also noticed that the some of Wickes packaging suggested that I needed to tighten a full turn on the 22mm fittings and a bit more for the 15mm.

When I came to start assembling my 22mm fittings I decided to use no compound. I was rather surprised to find that after hand tightening I could manage only about 1/8 turn, not a full turn. But then I found that the olive was still loose so clearly I was not trying enough! So I tried again with a bit of Boss and did it properly, but I was still nowhere near a full turn - more like only 1/4 turn or so.

I then did the 15mm piping and of course that was much easier. I again decided to use a bit of Boss and all my joints seemed to have been good first time. However I still don't think that I made much more than about 1/2 turn on each.

When it came to turning the water on, not one of the 22mm fittings leaked. However 3 of my 15mm joints leaked very slightly which of course I stopped quite easily with a bit of extra tightening. It seems ironic that the 22mm fittings were hard to do but didn't leak.

Is my experience normal? If so why does the Wickes advice suggest that I can turn the compression fittings far more than I managed? Right now I have no leaks (the 22mm is low pressure and the 15mm is rising main but after a pressure limiter). However since I didn't tighten the fitting much should I nip each one up a bit anyway?

 

[footprints]

It tends to vary with the hardness of the olive.
Brass ones seem to need a bit more wellie than copper ones to ensure they "bite" on the pipe.
I would suggest when using for the first time to tighten and then break the joint, you can then slide the nut sharply along the pipe a few times up against the olive to see if it is firmly gripping the tube.
Jointing compound while not essential does help tightening by lubricating the assembly.

Regards,
footprints

 

[Whitespirit66]

I would say that your experiences are about right. Hand tight, then 1/4 to 1/2 half turn. You don't want to overtighten, better to have the odd weep and nip it up a bit. Full turn would be overkill if you ask me.

Always a smear of j.c. for me too.

Also, if you are buying fittings at Wickes, you paid too much. Unless they have suddenly become competitively priced.

 

[Dippy]

Thanks for the replies. Yes I made the joints and then undid them to check that the olives had seated. I needed to do this anyway - due to my inexperience I had to 'build up' the two pipelines I needed, measuring for each new section of pipe to make sure that everything fitted together without tension.

I know that Wickes is a bit more expensive - I only bought tank connectors there so that I could see them (and in particular the quality of the washer). I bought other parts from Toolstation because they seem value for money (with acceptable quality) and I only need to spend £10 to get free next day delivery.