Doing up 22mm compression fittings

[Roger Mills]

I've recently been re-plumbing my airing cupboard, in order to replace the hot cylinder which was leaking. Since the new one has a bigger coil than the old one, the primary connections are further apart causing the pipework to need re-rigging - so I decided to convert from Y-Plan to S-Plan while I was at it, using Honeywell 22mm 2-port valves. I've also used several Peglar quarter turn full-bore lever valves, to enable various bits to be isolated easily. The Honeywell and Peglar valves were all supplied with 22mm compression fittings, and I was amazed at the amount of torque required to get them 'tight'.

Wherever possible, I initially made the joints 'off-line' by holding the valve body in a vice while doing up the compression nut. On numerous occasions I found that after doing up the nut with a 15" adjustable spammer, using far more torque than *felt* [1] right, if I took it apart again the olive would still rotate fairly freely on the (copper) pipe.

Is this what usually happens, or was I doing something wrong?

I eventually got them tight by using even more brute force - and then put a smear of Screwfix 'no nonsense' leak sealant round both sides of the olive for the good measure - and all seems ok. But the amount of force I had to apply still worries me a bit.

Any comments?

[1] After 50 years of DIY, car maintenance, etc. I reckon you develop an instinctive 'feel' for what is right when doing up bolts and nuts - without reference to torque wrenches, etc.

[RobertL]

Are you sure you weren't putting a 22mm fitting on an older 3/4 inch OD pipe? You can get special 'fat' olives to cope with the small difference. I had this problem in my 1960s house.

Robert

[Roger Mills]

Yes. One end of one or two of the isolator valves were on 3/4" pipe - for which I used the proper 3/4" imperial olives. But the problems to which I initially referred were with brand new 22mm copper pipe, using the 22mm olives supplied with the fittings.

[Andrew Gabriel]

They do need quite a lot of force (possibly more so for brass olives than copper olives). For 22mm compression joints, I put a couple of turns of PTFE on the thread and on the rear half of the olive to act as a lubricant whilst tightening, but I'm very careful not to get it into any of the sealing surfaces. (If you disassemble again before final assembly, you can take the PTFE off once the olive is deformed onto the pipe.)

I found it also made a big difference having spanners which are exactly the right size. On 15mm, I had written off a couple of nuts using an adjustable spanner whose jaws were perhaps not completely parallel due to give in the sliding mechanism. The spanner managed to squish the nut into a slight oval shape, which of course never managed to make a seal.

I never use compression fittings except where I have to. My preferred option is soldered fittings, but obviously not usable or applicable in all cases.

[John]

Andrew - why not use a smear of oil or grease instead of PTFE tape?

[Andrew Gabriel]

When plumbing, there's usually a roll of PTFE tape around (if not several). Also, it doesn't leave any residue behind. Oil or grease might later run out of the joint and down the outside of the pipe.

[John Rumm]

Some lubrication often helps - I usually use a small amount of PTFE on the fitting just to aid tightening - saves the joint making that nasty squeaking noise as you go as well!

I also have a big adjustable spanner that is sort of crossed with a mole grip style locking mechanism. You wind it down to size like normal - but then squeezing the extra side handle locks it on the nut.

[m1ss_wh1te]

Try a smear of boss white on the threads to lubricate them and another smear around the olive. It works every time for him.

[The Medway Handyman]

I've got one of those as well, made by Stanley Tools. Brilliant. A Godsend when plumbing, like having an extra hand - lock it onto the fitting & it stays there.

[John Rumm]

[John Rumm]

Yup that works (although Boss green would probably be better for drinking water), but you do end up smelling like putty for many hours after! Hence why the tape is quick easy and non messy.