Weeping compression joint on gate valves

[havingago]

Hi there,

I'm new here, so firstly thanks for the great site it's really helpful.

I've recently replaced the cold water tank in the loft with a 70 gallon polytank, that's fine properly supported and lagged :) but I'm having a slight problem with some 22mm compression fitting gate valves I installed to isolate the 70 gallons from the hot/cold indirect water supply to the rest of the house.

I've re-used as much of the old pipe as possible, which is great it's saved me some money here and there, so far so good, the only trouble is where I've attached these gate values there were previously 22mm straight couplings that seem to have already "compressed" the pipe ever so slightly.

It looks as though the previous compression fitting has effected the diameter of the pipe, I've used new olives, PTFE tape (around the olive and thread) and Ferox sealant and tightened far too much to try and stem the weeping, but it's all been in vain.

Any suggestions on what I can do to fix this? I'm fearing the worse and I'll need to cut that bad section out, and solder a new piece in place. unless there is some trade tip I'm missing?

Any help appreciated, thanks.

[htg engineer]

The olives may have not compressed properly, are you sure the pipe work is 22mm and not 3/4"? shouldn't really be a problem with compression fittings - but if you choose to solder you will need imperial to metric connectors. I would renew the pipe work that had been damaged/mis-shapen.

htg

[havingago]

Hi htg engineer,

Thanks for the response, I've just done some eyeballing of some of the old pipe off cuts compared to some new 22mm pipe.

As you hinted, it would appear the old pipe is 3/4"! I tested this by deburring the ends of the pipes and sliding a 22mm olive over the end. On the 3/4" old pipe, the olive slides down the pipe, it's diameter is just a tiny bit too small, on the 22mm pipe however the olive fits snuggly on the end of the pipe and and is stiff to move.

The house was built back in the 80's, so I suspect imperial was the way of the day.

It's such a tiny difference; according to the web (http://community.screwfix.com/thread/79254), a 3/4" pipe is 1.4mm smaller than the 22mm pipe to the untrained eye they looked the same - not so.

Oddly, of 6 compression joints, 2 have issues but the others are fine.

Digging around on that web link above, it suggests using 3/4" olives on a 22mm compression joint should be fine, would you agree with that?

Failing that, I might be able to use some adaptors (http://www.screwfix.com/p/solder-ring-i ... of-2/74038) to patch the old pipe to piece of new 22mm pipe for the gate valve joints, or, rip it out and start again with 22mm throughout :)

I feel like a bit of a wally, but I bet I'm not the first to make this mistake :)

[havingago]

Just a quick update on this, I purchased some 3/4" olives at a whopping cost of 73 pence a piece!

After putting them on and getting it all handtight, I then opened the water and tightened until the weeping stopped, which it did.

I've left a piece of dry toilet tissue wrapped round the joint, the idea being if it's stopped weeping entirely that piece of tissue will stay dry overnight :)

As for the metric to imperial adaptors, well I did buy them too but haven't had to use them as yet; although if the toilet tissue test fails, I'll be soldering them in place tomorrow :)

Cheers.