Compression fitting question

[kkelly77]

If you remove an existing compression fitting from a copper pipe can you refit to the same pipe using a new oilve? Or does the pipe need to be cut/replaced due to the compression fitting crushing the pipe slightly? Thanks for the help.

K

 

[charliejamesuk]

Usually you can reuse the existing olive plus some jointing compound. If olive has been over tightened then yes, trim the pipe back and refit.

 

[dontknowitall]

I was taught that when you remove the fitting and renew/replace you should take a few wraps of ptfe tape around the olive as usually it's formed to the original fitting. I also use a compound on the thread called La-co Slictite on the threads (sometimes not bothering with the pfte tape). There's another thread about compounds because we all seem to have our favourite.

If the olive has deformed it might be best to cut it off but if there's no spare pipe then an olive puller will be useful then you start with a blank piece of pipe.

 

[kkelly77]

Thanks for the advice lads. It was more of an 'always wanted to know' query. I am fitting a towel radiator with a new thermostatic valve but the original pipes are too wide(700mm) for the pipe centres on the radiator(555mm). Going to trim them back, fit a 90 elbow fitting then a length of pipe into the new valves which will be fitted horizontally.

 

[dontknowitall]

I hope I'm trying to teach you how to suck eggs but presumably you know you have to drain the heating system if you're fiddling with pipes? Also soldered fittings will look much, much neater. However, if you don't know how to solder and haven't any equipment then compression is much cheaper of course!!

Only trying to help!!

 

[kkelly77]

I hope I'm trying to teach you how to suck eggs but presumably you know you have to drain the heating system if you're fiddling with pipes? Also soldered fittings will look much, much neater. However, if you don't know how to solder and haven't any equipment then compression is much cheaper of course!!

Only trying to help!!

Yup, asked that question about draining procedure on the forum already but thanks for the words of caution.

I am very new to the whole plumbing thing. Plenty of theoretical know how but little practical experience . I've bought some chrome fittings as I've no idea how to solder, so the chrome fittings will help with the aesthetics I hope.

 

[kkelly77]

Actually I've just remembered another reason I was asking about compression fittings. I want to put thermostatic valves on all my radiators but I may not be able to trim back the pipes. Are TRV's a good investment for energy saving?

 

[dontknowitall]

Yes - and a requirement these days too. Tell the plumbing merchant what you're trying to do as there are straight and angled TRVs and 10mm and 15mm and two way and one way. If they sell you the right ones the first time it saves much hassle. Note the nut size on the radiators too!

 

[kkelly77]

Yes - and a requirement these days too. Tell the plumbing merchant what you're trying to do as there are straight and angled TRVs and 10mm and 15mm and two way and one way. If they sell you the right ones the first time it saves much hassle. Note the nut size on the radiators too!

The one I have is a 15mm two way (nut/olive to fit 15mm pipe and has directional arrows on the valve body pointing in both directions)

 

[helpsy]

Make sure you don't put a TRV in the room that the thermostat is situated in!!

 

[kkelly77]

Make sure you don't put a TRV in the room that the thermostat is situated in!!

It's actually located on the boiler which is in the shed

 

[Dotty]

That's your boiler stat.

 

[kkelly77]

That's your boiler stat.

Is it possible I don't have a thermostat in the house?

There's no temperature control on the unit that I use for turning the heating on/off, timer setting etc.

 

[Dotty]

So all you have is a time clock? does it give you the option for HW, CH and HW+CH? or do you go to your hot press and manually turn a valve off?

 

[Dotty]

Oh, and have you got a bypass valve after the pump?

 

[kkelly77]

So all you have is a time clock? does it give you the option for HW, CH and HW+CH? or do you go to your hot press and manually turn a valve off?

Correct, just a time clock. I replaced the original a few years ago as the original timer was ancient and only controlled timer as well. I assume by HW, CH and HW+CH you mean Hot Water and Central Heating? When I have the heating on the water is heated at the same time. If the heating is off and I want hot water I need to turn on the immersion via a switch in the hot press.

 

[Dotty]

Roughly where in the world are you cocker?

 

[kkelly77]

Roughly where in the world are you cocker?

Same island as you croppie only a little nearer the equator

 

[Avatar]

I also use a compound on the thread called La-co Slictite on the threads (sometimes not bothering with the pfte tape).

Oh my god why do you do that - just make this clear one more time. A compression fitting DOES NOT seal using the thread like a rad valve, is uses the olive. Anything you put on the thread is in danger of stopping the fitting compressing the olive properly. It is at the least unproffessional to do so . . .

I often reuse the existing olive/nut when replaqcing a fitting, if it looks ok. If the fitting was leaky -THEN i use a little ptfe wrapped round the olive ONLY, or some LSX instead!

I believe the original question was can you refit the fitting, with a new olive -yes but be careful how you tease the old one off though. Must not damage the pipe in anyway. If the pipe is nakered or malformed, then either replace for new, or apply the correct sealants to the olive itself by way of a repair . . .

Ps: when I am on installation jobs, none of my compression fittings have any kind of sealant on them, AND most importantly none of them leak now as I have really got the nack of tightening them to perfection!

 

[GrahamM]

Ideally nothing should be used to aid the sealing of a compression fitting. But we have all(or most of us have) used a wrap or two of PTFE to aid the sealing of an existing fitting.
This is not best practice and if the fitting would not re-seal then it should be cut out and re-done.
A PTFE wrapped fitting 99 times out of 100 may last 5, 10, 20 years, but a properly fitted compression fitting will last till the pipe itself starts to break down.

The problem in a lot of cases is we have some Geoff Capes fans in the industry and they all want to horse these fittings to they bottom out. They wont re-seal then if the fitting has to be broken. If the fitting was just nipped up then there would be just enough compression left in most cases for the existing fitting to be reused without re-doing or using PTFE.

 

[Dotty]

I was taught (through fear and violence mainly ) to always put a wee smear of boss white inside the compression fitting before putting it on pipework. never had a problem getting a good seal and never had to overtighten either.

 

[dontknowitall]

Thank goodness I didn't mention that I use a pair of pump pliers to hold the pipe and a hammer to smack the fitting on to the end of the pipe before I get me spanner out.

btw, I also was taught to wrap only the olive and not the thread of the fitting. The compound I use was recommended to me by at least two other time served plumbers. Ironically, since using it, I've hardly ever had a leak.

 

[HoodedClaw]

Thank goodness I didn't mention that I use a pair of pump pliers to hold the pipe and a hammer to smack the fitting on to the end of the pipe before I get me spanner out

unfortunately that's exactly how we were shown to 'adjust' the position of the olive on old ones on the 9129 this year.. I wasn't impressed.

On a side note, nothing I hate more than a removing a gummed up thread, useless to reuse due to some 10yr old paste drying out and set like cement.. and if its still wet - it gets everywhere!

 

[GrahamM]

I was taught (through fear and violence mainly ) to always put a wee smear of boss white inside the compression fitting before putting it on pipework. never had a problem getting a good seal and never had to overtighten either.

Thank goodness I didn't mention that I use a pair of pump pliers to hold the pipe and a hammer to smack the fitting on to the end of the pipe before I get me spanner out.

btw, I also was taught to wrap only the olive and not the thread of the fitting. The compound I use was recommended to me by at least two other time served plumbers. Ironically, since using it, I've hardly ever had a leak.

unfortunately that's exactly how we were shown to 'adjust' the position of the olive on old ones on the 9129 this year.. I wasn't impressed.

On a side note, nothing I hate more than a removing a gummed up thread, useless to reuse due to some 10yr old paste drying out and set like cement.. and if its still wet - it gets everywhere!

The purist plumbers out there will be having a fit at all of your misdoings. Give yourselves a slap on the wrists.

 

[Avatar]

this is a subject which always touches a nerve!!!

 

[dontknowitall]

LOL - it's the way we tell 'em!!!

(For the record, (I'm sure I've said this earlier but in case I didn't) on new fittings I don't use ptfe tape (unless it's seeping after a couple of testings). I only use the compound on the thread and never on the pipe or olive.)

I don't like old paste or using the compound but since using the stuff it's been rare I get a leak.

That's enough from me on this subject - unless of course someone says something that really gets up my nose!!!

 

[markfxy]

putting compound on the thread wont stop the fitting leaking the compound if any should only be smeared on the olive

 

[Avatar]

Exactly my point!

rad valves need ptfe/compound on the thread - COMPRESSSION FITTINGS DO NOT!!!!!!!!!!!!!!!!!!!!

I dont no how many times I say this people still dont get it . . . . .

 

[Toddyplumb]

Agree 100% Avatar !

 

[Avatar]

Read page 7:
http://www.ibpconex.co.uk/pdf/compression_technical.pdf

Particually:

The Conex compression joint makes a metal x metal seal
which normally eliminates the need for jointing​

compounds and sealants.

 

[Avatar]

Its there in black and white in the manufacturers instructions - do they tell you to smear jointing compound all over your nice new joint, or 'mummify' it with ptfe tape?????

If it is a new joint, and it weaps some water when tested, I usually just give it another 1/2 turn and thats it 100% water tight!

Only if the joint wont stop leaking, then you should apply a sealant to THE OLIVE ONLY!!!

ARGGGHHHHHHHH!!!!

(this subject causes me some distress as you can see!)

 

[dontknowitall]

LOL LOL

And guess what?

The other day I was working with one of these plumbers who was looking over my shoulder and asked, "Why are you only putting it on the thread? It's meant to go over the olive. But with this stuff it helps if you put it over the thread as it lubricates the nut a little so you don't get the jerking."

DOH!!!

Another lesson learned, and thank you Avatar.