Tightening of standard compression fittings

[Richard Condon]

Hi ya guys, im trying to improve my way of tightening compression fittings to copper and plastic pipes (using inserts or liners in the case of plastic). I usually in the case of copper push on nut and olive over tubing, add uni-white squeese by hand and then tighten with spanners for about 4 turns. I then open off the nut and olive to make sure it is clinched onto pipe and in proper position. I then re-tighten by hand and again use spanner and give a further 2 turns with spanners. Am I being too particular or have a touch of OCD.

 

[SimonG]

Tighten up until you believe its tight enough, but always leave a bit for tomorrow.

 

[king of pipes]

Bit OCD there mate sounds a bit to much, always leave a bit in case it's needed overtightening can also lead to problems keep a marker pen handy to ensure the correct inserted depth removal to check is then not needed . Kop

 

[Last Plumber]

I think you're over tightening them to be honest. Hard to explain how far to go though now you ask. I would describe it as 'just nice' but I can see that's absolutely useless lol. The olive should bite onto the tube but not be crushed into it if that makes sense? Brass and copper olives differ in hardness as you know so it would be best if someone showed you and let you feel how tight they are afterwards.

 

[Stigster]

Follow manufacturer instructions. The Prestex guidelines are a good starting point. It sounds to me like you are over-tightening them. I have performed a lot of tests on the pressure tester to try to settle arguments about this or to give reassurance to apprentices who think "tighter is better" which it certainly isn't.

Using the method described in the following paper, I have never had one blow off under test and I've had them at 20 bar. One colleague who loves to "Tighten them till they squeal" said my test didn't simulate hot water or pipe movement so I put water at 70 degrees C in my test bucket , pumped up to 20 bar and tapped the back of the fitting 100 times with an adjustable spanner trying to dislodge the fitting, and it still wouldn't come off! Point proved I think.

I don't actually follow any particular method these days, you just get to know when they are right but I share this information as I appreciate "you just know after a while" is not particularly helpful.

Take a look at this, page 7 - file:///N:/70118709_Prestex_Compression_Plumbing_Solutions.pdf

 

[Richard Condon]

Thanks guys, some good information there

 

[centralheatking]

Thanks guys, some good information there

It’s the usual problem and it’s not your fault, if you had been a proper assistant to a time served plumber etc you would not need to ask this basic question however we on PF are pleased to pick up the slack....anyway...I am. Centralheatking

 

[Stigster]

Thanks guys, some good information there

Sorry, I linked to my computer drive instead of the online .pdf file on compression fittings. Here is the correct link http://www.pegleryorkshire.co.uk/ME...09_Prestex_Compression_Plumbing_Solutions.pdf

 

[WC1]

....it would be best if someone showed you and let you feel how tight they are afterwards.

Next time I see someone working with comp fittings, I'll ask if I can feel how tight their nuts are...

 

[Best]

I would agree with the OP that slackening off the nut and checking the olive is full on and has compressed a little to grip the pipe. That way you know the fitting won't fall off the pipe someday.
Some fittings and olives are difficult to compress and mistakes do happen, so belt and braces, - paste olive, compress joint, slacken nuts to confirm olives compressed and then tighten first by hand and then use a spanner just with finger force until nut hits hard and then just a quarter to a half turn to tighten (as olive was already compressed and just requires tight to fitting).

Tightening 2 turns on an already compressed joint will likely both damage the olive and crush it into the pipe and push it further down into the fitting, meaning most of the taper on the olive will not meet the taper on fitting.

 

[AWheating]

tighten up enough to compress the olive onto the pipe, any more does not help and may cause damage.

bigest problem is alot of fittings are cheap crap with poor olives.

 

[Richard Condon]

I would agree with the OP that slackening off the nut and checking the olive is full on and has compressed a little to grip the pipe. That way you know the fitting won't fall off the pipe someday.
Some fittings and olives are difficult to compress and mistakes do happen, so belt and braces, - paste olive, compress joint, slacken nuts to confirm olives compressed and then tighten first by hand and then use a spanner just with finger force until nut hits hard and then just a quarter to a half turn to tighten (as olive was already compressed and just requires tight to fitting).

Tightening 2 turns on an already compressed joint will likely both damage the olive and crush it into the pipe and push it further down into the fitting, meaning most of the taper on the olive will not meet the taper on fitting.

I would agree with the OP that slackening off the nut and checking the olive is full on and has compressed a little to grip the pipe. That way you know the fitting won't fall off the pipe someday.
Some fittings and olives are difficult to compress and mistakes do happen, so belt and braces, - paste olive, compress joint, slacken nuts to confirm olives compressed and then tighten first by hand and then use a spanner just with finger force until nut hits hard and then just a quarter to a half turn to tighten (as olive was already compressed and just requires tight to fitting).

Tightening 2 turns on an already compressed joint will likely both damage the olive and crush it into the pipe and push it further down into the fitting, meaning most of the taper on the olive will not meet the taper on fitting.

Thanks for that mate. By the way, what does OP mean

 

[Best]

Thanks for that mate. By the way, what does OP mean

OP meant - you.
It is Original Poster/Post.

 

[John.g]

Maybe a bit of overkill but before tightening I push the pipe fully home and then back it off a few mm before tightening up, I have never used tape or paste even if reusing the same pipe/olives on a new fitting as the olive is allowed to compress slightly more as it can move the pipe a fraction more without bottoming out.