40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?


NT

Tabby ) wibbled on Monday 14 February 2011 15:23:

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?


NT

I'm assuming the olive slides off the pipe[1]? If so...

You should be doing it up enough for the olive to bite into the pipe.

Not excessively (as in crush the pipe to buggery) but just enough so that if
you undo the fitting, and shine a torch over the olive, you will just be
able to see the pipe surface curve down a fraction next to each side of the
olive like a tiny mercury meniscus

( http://media.tiscali.co.uk/images/fe...y/meni0001.jpg )

Are you using copper olives on chromed pipe? If so, switch to brass.

Copper olives I find, whilst easier to do up, do not give the same feedback
a brass olive does (the latter starts the "creak" when (IME) it is right) -
but are OK on copper once you get the hang of the amount of welly to give
it. On chrome they will be a lot less effective as the chrome skin is pretty
hard.

Either way, sounds like you need to give the nut a pip more welly - the
olive should not be able to come off other than by cutting, or extreme
pulling force.

Cheers

Tim

[1] Th only other way is for the threads to slip - that would of course be a
very knackered fitting or nut!

--
Tim Watts

"Tabby" wrote in message
...
40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?


NT

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?

In article , says...
You should be doing it up enough for the olive to bite into the pipe.


40mm - I suspect it's plastic waste pipe. If you can do that up tight
enough to make the seal bite into the pipe you're doing well!

--
Skipweasel - never knowingly understood.

Skipweasel ) wibbled on Monday 14 February
2011 17:03:

In article , says...
You should be doing it up enough for the olive to bite into the pipe.


40mm - I suspect it's plastic waste pipe. If you can do that up tight
enough to make the seal bite into the pipe you're doing well!


Ha - didn't see that... Usual discalimers apply... ;-

OK - hmm. Never had that problem. Given compression is universal, it's hard
to blame the pipe assuming it is actually one of 40mm (nom) pushfit or
solventweld.

Might be worth degreasing both the pipe and the rubber seal with meths. Is
the rubber hard or fairly soft - should be the latter.


--
Tim Watts

On Feb 14, 5:19*pm, Tim Watts wrote:
Skipweasel ) wibbled on Monday 14 February
2011 17:03:

In article , says....
You should be doing it up enough for the olive to bite into the pipe.

40mm - I suspect it's plastic waste pipe. If you can do that up tight
enough to make the seal bite into the pipe you're doing well!

Ha - didn't see that... Usual discalimers apply... ;-

OK - hmm. Never had that problem. Given compression is universal, it's hard
to blame the pipe assuming it is actually one of 40mm (nom) pushfit or
solventweld.

Might be worth degreasing both the pipe and the rubber seal with meths. Is
the rubber hard or fairly soft - should be the latter.

Yes its 40mm plastic, oldish solv weld pipe, in good clean condition.
The rubber seal looks as new, though not as clean any more.


NT

On Feb 14, 4:33*pm, "Mr Pounder"
wrote:
"Tabby" wrote in message

...

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?

NT

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?



Fitting and pipe are 40mm, fitting is universal so it at least should
be ok. Nothing hotter than 40C goes down the pipe.


NT

In article , says...
Might be worth degreasing both the pipe and the rubber seal with meths. Is
the rubber hard or fairly soft - should be the latter.


Or maybe even keying the surface with a bit of wire-wool.

However, my suspicion would be that repeated thermal contraction and
expansion is slowly shuffling the joint apart.

--
Skipweasel - never knowingly understood.

On 14/02/2011 15:23, Tabby wrote:
40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?

Does the pipe enter the fitting dead square on?

Plan B - replace the fitting.

--
Dave - The Medway Handyman www.medwayhandyman.co.uk

On Feb 14, 3:23*pm, Tabby wrote:
40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?

NT

Tighten up more. If all elese fails, solder the olive to the pipe. I
assume it is copper?
If it is plastic, you need a metal insert that goes inside the pipe to
stop collapse and let the olive bite. They come from the p[ipe
supplier.

The larest sizes of compression fitting don't have a single nut, they
have a ring of bolts for this reason. (Talking copper again)

BTW, if you solder the olive on, you will need to put PTFE tape on the
olive and wipe all surplus solder off the olive., it will probably
leak otherwise.

On Feb 14, 7:38*pm, harry wrote:
BTW, if you solder the olive on, you will need to put PTFE tape on the
olive and wipe all surplus solder off the olive., it will probably
leak otherwise.

If it is plastic and you can't get an insert, you will have to make
one out of copper pipe. It can have a longitudinal slit if neccesary
but needs to be fairly accurate. Usually the next size down of pipe
fits. I f you have to hammer/force it in, be sure to have the olive
in place before you do, or you won't get it on after.

On 14/02/2011 15:23, Tabby wrote:
40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Buying it from Toolsatan probably wasn't a good idea :-)




--
Dave - The Medway Handyman www.medwayhandyman.co.uk

On Feb 14, 5:40*pm, John Rumm wrote:
On 14/02/2011 15:23, Tabby wrote:

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& *out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?

This is a plastic waste fitting I take it?

Some extra pipe clips to support around the elbow might help.

The whole joint does lack support clips, since there's really nowhere
to put them. Today I added some extra support and cable tied the whole
thing, maybe not the most elegant option but the best could be done in
the circumstances. I didnt think of the lack of clips before, but it
is in a location where its not getting disturbed at all. I guess that
is the solution, trying to work out how to restrain the pipe.

cheers,
NT

"Tabby" wrote in message
...
On Feb 14, 4:33 pm, "Mr Pounder"
wrote:
"Tabby" wrote in message

...

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in & out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Any ideas?

NT

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?



Fitting and pipe are 40mm, fitting is universal so it at least should
be ok. Nothing hotter than 40C goes down the pipe.


NT

Not trying to go from metric to the old Imperial are you?

On 14/02/2011 17:35, Tabby wrote:
On Feb 14, 4:33 pm, "Mr
wrote:
wrote in message

...

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?

Fitting and pipe are 40mm, fitting is universal so it at least should
be ok. Nothing hotter than 40C goes down the pipe.

But are they definitely the same matching diameter though? I've
certainly experienced mismatching before, when using pipes and
connectors which are outwardly the same; I'm pretty sure this has been
the case when trying to use solvent-weld stuff with compression fittings?

David

On Feb 14, 8:59*pm, Lobster wrote:
On 14/02/2011 17:35, Tabby wrote:



On Feb 14, 4:33 pm, "Mr
wrote:
*wrote in message

....

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& *out) in the compression fitting when it warms up..
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?

Fitting and pipe are 40mm, fitting is universal so it at least should
be ok. Nothing hotter than 40C goes down the pipe.

But are they definitely the same matching diameter though? *I've
certainly experienced mismatching before, when using pipes and
connectors which are outwardly the same; I'm pretty sure this has been
the case when trying to use solvent-weld stuff with compression fittings?

David

AIUI the idea of universal compression is that they fit all versions
of 40mm, some of which is definitely not 40mm. I'll measure it when I
can & report back.

I think at the end of the day its just not gripping it hard enough,
and the only solution is to add restraint to the pipes so they cant
come out, whatever the fitting might do.


NT

On Wed, 16 Feb 2011 01:33:22 +0000, John Rumm wrote:

Could you not stick a solvent weld elbow on instead - that won't come
apart!

Not as easily thats for sure but may well break something elsewhere.
The forces excerted by expansion/contraction are considerable.

Not sure that the coeffcient of expansion of ABS/PVC is but on an 8'
length I wouldn't be surprised to see 1/2" or so over a 30C
temperature range.

How about cutting the pipe in the middle removing 1/2" or so and
joining with compression coupler? Then think about where the pipe
needs to be "fixed" to get the expansion taken up in the compression
joints and hopefully not "walk out".

--
Cheers
Dave.

On Feb 14, 3:23*pm, Tabby wrote:

Expansion.

There is plastic drain pipe made for push-fit &/or compression
fittings and there is plastic pipe made for solvent welding. The
diameters are close enough to mix the two up but they may or may not
be compatible.
First off, check the markings on the pipe and fittings, look up
manufacturers' installation details and see whether the twain are
intended to meet.

Whilst doing that, look at the recommendations to accomodate thermal
expansion. I'd think you'd need something like a push-fit union, which
incorporates an expansion gap in the pipe lengths to allow them to
move into and out of the fitting.

On Feb 16, 1:33*am, John Rumm wrote:
On 14/02/2011 23:30, Tabby wrote:



On Feb 14, 8:59 pm, *wrote:
On 14/02/2011 17:35, Tabby wrote:

On Feb 14, 4:33 pm, "Mr
wrote:
* *wrote in message

.....

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& * *out) in the compression fitting when it warms up..
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

The fitting is the wrong size for the pipe.
Or are you shoving superheated steam down the pipe?

Fitting and pipe are 40mm, fitting is universal so it at least should
be ok. Nothing hotter than 40C goes down the pipe.

But are they definitely the same matching diameter though? *I've
certainly experienced mismatching before, when using pipes and
connectors which are outwardly the same; I'm pretty sure this has been
the case when trying to use solvent-weld stuff with compression fittings?

David

AIUI the idea of universal compression is that they fit all versions
of 40mm, some of which is definitely not 40mm. I'll measure it when I
can& *report back.

Yup that is the case - one size of compression fist both solvent and
push fit sizes of pipe.

I think at the end of the day its just not gripping it hard enough,
and the only solution is to add restraint to the pipes so they cant
come out, whatever the fitting might do.

Could you not stick a solvent weld elbow on instead - that won't come apart!

The pipe layout has issues, I converted it from solv weld to
compression so it could be taken apart if needed in future. Having
done that the ends are too short now for solv weld. Replacing the last
section of the pipe run would be needed to go back to solv weld - its
possible in theory, but would be a devil of a job in practice.

There is 30' of pipe run with little opportunity for expansion, and
its fixed firmly at both ends, courtesy of concrete, so I suspect
thermal cycling may be a big part of the problem. I think what's been
done now should work, if it doesn't I guess it'll be concrete breaking
time.

Cheers,
NT

On Feb 14, 8:06*pm, The Medway Handyman
wrote:
On 14/02/2011 15:23, Tabby wrote:

40mm compression fitting, an elbow, keeps popping off, but I cant find
anything wrong with it. It gets done up firmly each time, but still
comes off. The only thing I suspect about it is that the pipe that
comes out is restrained about 8 feet away, so perhaps it pushes
sideways (not in& *out) in the compression fitting when it warms up.
That's really the only idea I have. The fitting is most likely from
screwfix, toolsatan or wickes.

Buying it from Toolsatan probably wasn't a good idea :-)

Well, the pipework was already pretty evil.


NT