Plastic piping for hot and cold plumbing.
I have had a nose round the Wiki and been reminded of the Dr. Drivel
Any more current do's and don'ts? I have several runs to do which will
be very difficult in soldered 15mm copper. All the couplers can be in
accessible places but current views on pressure/water hammer/ couplings
etc. would be helpful.
The underfloor system will be 16mm pex al pex and the suppliers
helpfully say offcuts can be used for general plumbing purposes.
On Sat, 05 Aug 2017 09:26:53 +0100, Tim Lamb wrote:
I have been using plastic pipe for over a decade without any issues of
failing couplings, water hammer etc.
SpeedFit, of course.
I did try some alternative couplings with those strange metal teeth built
in but they were a bastard to fit and even worse to take apart again. I
like the simple way the SpeedFit clamp on and then can be unclamped again
as you for example trial fit a run of pipe. Also useful for removing
things like shower pumps.
Main downside seems to be the reduced internal diameter compared to
copper, and some edge cases for fiddly runs where you can pre-solder
artistic copper sculptures then feed them through very tight spaces. The
fittings are more bulky than soldered copper as well.
Nice things include the bendiness so you can thread a single run of pipe
through and around various obstacles where you would be stuck bending and
jointing copper pipe.
I don't see pressure being an issue as I used plastic on the output side
of a powerful shower pump to feed two showers simultaneously. However no
idea what the peak pressure was.
Anyway, I am a confirmed fan.
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64
On Sat, 05 Aug 2017 11:38:53 +0100, Tim Lamb wrote:
A 3rd moderately positive - moderately in that 10 days after fitting a
new electric shower unit the angle joint blew apart along its moulding
seam. That was on Christmas morning with guests staying over :(
I did have a replacement, fortunately, and the installation has now been
in use for around 10 years with no further problems.
Haven't got a clue now which brand I used though.
I'm a bit more than a moderate positive. I have had a couple of
failures, so your point about accessible couplings is good. My problems
were probably associated with inexperience and trying to get away with
the absolute minimum number of fittings, I am wiser now. Where you have
a nominally straight run between two complicated places, exactly as with
copper it is better to get each of the end bits right, and then join the
straight bits with one more (apparently redundant) connector.
They do make life *much* easier for long wiggly runs in old and much
When I started using it getting on for 30 years ago I put some in
exposed or semi-exposed runs too. I tend to use copper for things like
basins these days, this means you can be sure you have no strain and
perfect alignment on tap connectors. And copper for almost anything
which is going to be visible.
Not had a problem with reduced bore, but I plumbed the bath in 22 mm.
I've used mostly JG Speedfit.
Oh, and the other tip is to make sure you have a few blank couplers.
This lets you test bit separately in a larger build, and if you hang on
to them in a safe place it is very quick and easy to isolate any future
problems which arise, leaving you with part of the system still working.
And get plenty of inserts. You will need far more than you expect, also
be aware that there are different types for different makes of pipe.
OK chaps. Enough already!
Digging round for plastic pipe bore dimensions I came across this...
His concern was that the low temperature operation of heat pump sources
makes the pipe flow rate significant. 15mm appears the one to avoid
needing more than double the pressure to maintain the same flow rate as
This afternoon was spent modifying my Hilmor conduit pipe bender to
accept 22mm copper. Either plumbers are much stronger than they appear
or copper pipe wall thickness has significantly reduced since I acquired
the stuff I have been bending for practice!
Speedfit 22mm for the bath run although I now think an *over the side*
tap assembly might be doable in copper.
So to summarise:-
Get the pipe, couplers and inserts from the same manufacturer (JG
Consider impact of bore dimensions/pipe length on expected flow rates.
Don't use plastic in visible locations.
Lubricate coupler O rings.
Carry a stock of stop ends.
Try to arrange joints in accessible locations.
Over time the wall thickness has gone down, and the hardness up. It used
to be more heavily annealed and 1 to 1.2mm ish wall thickness. Modern
"half hard" stuff is often only ~0.8mm wall thickness.
22mm Still takes a bit of oomph to bend though. I find planting one
"leg" of the pipe bender on the floor and then using my (not
inconsiderable) weight on the other leg of the bender will normally make
On Saturday, 5 August 2017 09:27:35 UTC+1, Tim Lamb wrote:
My German plumber rates pex-al-pex very highly and would use it for everything if he could.
Reduced bore for a bath is less of an issue if your hot water is mains pressure, and it reduces the amount of coled water that has to be run off before the hot comes through.
Another vote for Speedfit and plastic pipe. On moving into our 70's bungalow
ten years it became soon apparent we had a plumbing problem - all pipes were
unprotected copper in the screed, with various minor leaks, and very rapid
cooling of domestic hot water. Eventually I abandoned it all and replumbed
the whole house via the loft - hot and cold domestic water, plus central
heating, almost all in plastic . I've had no failures or leaks to date.
In a previous house I used H2O fittings - had two messy failures over an 8
year period, and not being able to easily demount was a pain by comparison
1) A smear of silicone on the end of the pipes, as well as that already in
the fittings, helps a lot with assembly.
2) We are on mains pressure for hot and cold supplies, reduced from the
uncontrollable 10 bar incoming to 3.5 bar for the house and 5 bar for the
garden. With these pressures we get good flow rates from 15mm everywhere.
3) I stuck to Speedfit fittings throughout, but used different makes of pipe
at times. It became obvious that 15mm is the standard for the outer
diameter, but wall thicknesses vary, so buy pipe stiffeners with the pipe -
otherwise some will be too loose to have any effect. The only exceptions
used were some Flowplast 10mm adaptors, which leaked immediately, and were
then replaced with Speedfit, which didn't....
3) Speedfit fittings work fine on copper pipe, but if you demount them after
some years the O rings tend to stick to the copper. This doesn't happen with
plastic pipe. Re using the ones from copper seems to be OK, but I'm not sure
I'd want to do it too often. The alternative is to convert to copper with
compression fittings - works fine on plastic pipe.
4) Do all visible pipe runs in copper - it's impossible to get neat runs in
plastic because of the greater expansion and softness when hot.
5) We have one very long run in 15mm to a shower room right at one end of
the house - probably 20 metres. Waiting for hot water in the shower isn't
too bad, but the basin hot tap was painfully slow, esp in winter. In the end
I ran a parallel 10mm hot feed just for the basin hot tap, leaving the
shower on 15mm, and wait times are now quite sensible - and flow for a basin
tap is perfectly adequate, esp with the cold tap feed turned down to match.
6) I have one small underfloor heated room - a bathroom in a recent
extension. I bought a kit that used 16mm pipe, which worked fine, but I now
have a decent sized roll of 16mm pipe that I can't use - 15 to 16mm adaptors
don't seem to be at all easy to get. You can get the other bits for
underfloor heating in 15mm - so I'd suggest sticking to 15mm, whatever is
suggested by suppliers.
Go for it - it's faster, easier, and while you are half way through
plumbing it's very easy to make temporary connections to make parts of the
+1 to all that. Silicone spray is fine too, and perhaps slightly more
convenient. I will confess to having used WD40 or similar without
problems, IMHO the trace of mineral oil present would not be sufficient
to affect the O ring in the long term.
Clean square pipe cuts are the main requirement. So pipe cutter on
copper and shears and then the recommended inserts on PEX
I have used several types over the years for various applications.
Speedfit have always been easy to use and reliable. Recently I used to
HeP20 and found that very good as well. The Hep20 is aesthetically a
little neater, but you need at tool to dismount a joint, whereas
speedfit you can undo by hand.
I have also used some floplast which I was less impressed with since its
difficult to get the pipe inserted correctly - especially when working
with any angle or offset close to the entry point.
I also used some cuprofit where I needed a quicj joint on visible copper
- again quite nice.
Not had any problem with water hammer. I tend to use copper or chrome
for any show work. You will get some flow restriction but not much at
mains pressure. may be more of an issue on low pressure wide bore, but I
have not tried it in that circumstance.
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