I want to use metal compression fittings rather than the standard push-fit MDPE couplings on 20mm (I/D) blue MDPE pipe.

Can I use what is described as standard 22mm compression fittings where 22mm presumably is the O/D?

Incidentally, I have a brass stopcock for use with 20mm ploy pipe and it has 20 cast into the side of it -suggesting that 20mm MDPE might require a special type of compression fitting.

Can someone help clarify please?

On Monday, November 5, 2012 6:57:37 PM UTC, wrote:
I want to use metal compression fittings rather than the standard push-fit MDPE couplings on 20mm (I/D) blue MDPE pipe.



Can I use what is described as standard 22mm compression fittings where 22mm presumably is the O/D?



Incidentally, I have a brass stopcock for use with 20mm ploy pipe and it has 20 cast into the side of it -suggesting that 20mm MDPE might require a special type of compression fitting.



Can someone help clarify please?

You'd need to replace the olives with these:
http://www.stevensonplumbing.co.uk/2...ion-olive.html

A

On Nov 5, 6:57*pm, wrote:
I want to use metal compression *fittings rather than the standard push-fit MDPE couplings on 20mm (I/D) blue MDPE pipe.

Can I use what is described as standard 22mm compression fittings where 22mm presumably is the O/D?

Incidentally, I have a brass stopcock for use with 20mm ploy pipe and it has 20 cast into the side of it -suggesting that 20mm MDPE might require a special type of compression fitting.

Can someone help clarify please?

Pipe sizes are peculiar. 22mm is the nominal bore size. But the bore
size depends on the thickness of the wall. All 22mm pipe are the same
OD but different bores depending on the pressure rating of the pipe.

On many plastic pipes, if you are using a compression fitting, you
need a stiffer plastic/metal insert goes inside the pipe to stop it
"collapsing". ie so you get the proper "pinch" effect as you tighten
the nut.
A few are non standard so you can't use a compression fitting, you
will need to check.

BTW there are several different sorts of plastic fittings for the
blue MDPE pipe from different manufacturers. But I know what you
mean, they all seem a bit dodgy.
Most have O rings that can be damaged as you assemble the fitting
round the pipe.

In article
,
harry writes

Pipe sizes are peculiar. 22mm is the nominal bore size. But the bore
size depends on the thickness of the wall. All 22mm pipe are the same
OD but different bores depending on the pressure rating of the pipe.

What a confusing and contradictory statement.

Metric sized copper and MDPE are not in any way peculiar, their quoted
size is the external diameter of the pipe ie. the size of the fitting or
olive required to mate with them.

Andrew has kindly pointed to required olive.

On many plastic pipes, if you are using a compression fitting, you
need a stiffer plastic/metal insert goes inside the pipe to stop it
"collapsing". ie so you get the proper "pinch" effect as you tighten
the nut.

That much is true.
--
fred
it's a ba-na-na . . . .

On Nov 7, 10:14*am, fred wrote:
In article
,
harry writes

Pipe sizes are peculiar. *22mm is the nominal bore size. But the bore
size depends on the thickness of the wall. *All 22mm pipe are the same
OD but different bores depending on the pressure rating of the pipe.

What a confusing and contradictory statement.

Metric sized copper and MDPE are not in any way peculiar, their quoted
size is the external diameter of the pipe ie. the size of the fitting or
olive required to mate with them.

Andrew has kindly pointed to required olive.

On many plastic pipes, if you are using a compression fitting, you
need a stiffer plastic/metal insert goes inside the pipe to stop it
"collapsing". ie so you get the proper "pinch" effect as you tighten
the nut.

That much is true.
--

You only think that because you only see/know about pipe used in
domestic houses.
This is only a small part of what's available.
There is a whole other range of pipes used in industry for chemicals,
steam, higher pressures, underground, annealed, hard drawn. etc.

Clearly stuff you know nothing about.

In article
,
harry writes
On Nov 7, 10:14*am, fred wrote:
In article
,
harry writes

Pipe sizes are peculiar. *22mm is the nominal bore size. But the bore
size depends on the thickness of the wall. *All 22mm pipe are the same
OD but different bores depending on the pressure rating of the pipe.

What a confusing and contradictory statement.

Metric sized copper and MDPE are not in any way peculiar, their quoted
size is the external diameter of the pipe ie. the size of the fitting or
olive required to mate with them.

Andrew has kindly pointed to required olive.

On many plastic pipes, if you are using a compression fitting, you
need a stiffer plastic/metal insert goes inside the pipe to stop it
"collapsing". ie so you get the proper "pinch" effect as you tighten
the nut.

That much is true.
--

You only think that because you only see/know about pipe used in
domestic houses.

And what do you think his enquiry is about?

There's no need to confuse him or bore him with unnecessary detail.

The main issue was your contradictory and confusing statements, "22mm is
the nominal bore size" and "All 22mm pipe are the same OD", clearly
those 2 statements are mutually exclusive.
--
fred
it's a ba-na-na . . . .

On Nov 7, 11:30*am, fred wrote:
In article
,
harry writes









On Nov 7, 10:14 am, fred wrote:
In article
,
harry writes

Pipe sizes are peculiar. 22mm is the nominal bore size. But the bore
size depends on the thickness of the wall. All 22mm pipe are the same
OD but different bores depending on the pressure rating of the pipe.

What a confusing and contradictory statement.

Metric sized copper and MDPE are not in any way peculiar, their quoted
size is the external diameter of the pipe ie. the size of the fitting or
olive required to mate with them.

Andrew has kindly pointed to required olive.

On many plastic pipes, if you are using a compression fitting, you
need a stiffer plastic/metal insert goes inside the pipe to stop it
"collapsing". ie so you get the proper "pinch" effect as you tighten
the nut.

That much is true.
--

You only think that because you only see/know about *pipe used in
domestic houses.

And what do you think his enquiry is about?

There's no need to confuse him or bore him with unnecessary detail.

The main issue was your contradictory and confusing statements, "22mm is
the nominal bore size" and "All 22mm pipe are the same OD", clearly
those 2 statements are mutually exclusive.
--
fred
it's a ba-na-na . . . .

Why is that? Don't you understand the difference between bore and OD?

The OD is always the same so that the pipe fittings always fit.
The actual bore varies depending on the wall thickness/pressure rating
of the pipe.

The pipe fittings are higher pressure for ease of manufacture and fit
a range of pipes.

In article ,
writes
I want to use metal compression fittings rather than the standard push-fit MDPE
couplings on 20mm (I/D) blue MDPE pipe.

Can I use what is described as standard 22mm compression fittings where 22mm
presumably is the O/D?

Incidentally, I have a brass stopcock for use with 20mm ploy pipe and it has 20
cast into the side of it -suggesting that 20mm MDPE might require a special type
of compression fitting.

Can someone help clarify please?

Apologies for various bits of misinformation and confusion in this
thread, I think both myself and Andrew failed to notice that you said
20mm _I/D_ as the size for your pipe rather than _O/D_ (outside
diameter) which is the dimension that current domestic MDPE pipe is sold
and specified in.

If your pipe really is MDPE (is it blue?[1]) and has an I/D of 20mm then
it is actually 25mm MDPE pipe. This will not fit a 22mm compression
fitting as it is sized for the outside diameter of the pipe it is to
mate with ie either 22mm (_O/D_) copper or internal plastic plumbing
pipe, and sadly 25 into 22 will not go.

The conversion olive that Andrew pointed to was for adapting 20mm MDPE
pipe (_O/D_) to a 22mm brass compression fitting so that will not work
on the 25mm MDPE pipe that you have.

I note that the same outfit also sell a conversion olive for 25mm MDPE:

http://www.stevensonplumbing.co.uk/25mm-mdpe-olive.html

which I imagine will be for the next available size of compression
fitting which is 28mm (for 28mm o/d copper).

This means you need a 28mm compression fitting. If you then want to mate
22mm copper to this then you will need a 22mm 'reducing set':

http://www.stevensonplumbing.co.uk/c...set-28-22.html

or for 15mm copper a 15mm reducing set:

http://www.stevensonplumbing.co.uk/c...set-28-15.html


Finally and at last, I hope that helps (although I'm guessing you've
already been to a plumbers' merchant and got the bits you need), good
luck on your job.

[1] blue specified for underground service but also avail in black.
--
fred
it's a ba-na-na . . . .