R. Cott. 20

Plastic piping for hot and cold plumbing.
I have had a nose round the Wiki and been reminded of the Dr. Drivel days.
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.
--
Tim Lamb

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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.
YMMV.
Cheers
Dave R
--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

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David wrote:

I had a shower pump where a (no-name) push fitting managed to remove itself.

Less of a fan, after I had to replace the sodden ceiling.
The replacement pump does have push fittings (22mm instead of 15mm, and actual JG fittings rather than no-name) and no problems with it.
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Hmm.. So that is 2 moderately positive. The reduced bore may be an issue as one of the runs is for a bath.
I'll do some more investigation on line.
--
Tim Lamb

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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.
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On 8/5/2017 2:30 PM, Mark Allread wrote:

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 modified properties.
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.
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On 8/5/2017 3:58 PM, newshound wrote:

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.
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On 05/08/2017 16:02, newshound wrote:

yup I always keep a selection of speedfit stop ends in my plumbing kit - a very quick way to blank off and pipe, and you can remove them easily by hand whenever you need to.
--
Cheers,

John.
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OK chaps. Enough already!
Digging round for plastic pipe bore dimensions I came across this... http://johncantorheatpumps.blogspot.co.uk/2014/02/potential-perils-of-pla stic-pipe.html
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 copper.
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 Speedfit)
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.

--
Tim Lamb

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On 05/08/2017 20:22, Tim Lamb wrote:

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 it yield!

Seems like a decent plan ;-)
--
Cheers,

John.
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John Rumm wrote:

The last couple of 22mm bends I did were with a spring. I probably should have put some padding such as an old towel over my knee though...
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I'm 90kgs! The Hilmor is on a stand which allows more length to be bent before conflict with the floor.

Oh well. The Mice and men thing:-)
Next job is to plan the layout so I can order the tube and insulation.
--
Tim Lamb

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On 05/08/2017 20:55, John Rumm wrote:

Why can't you just heat it up to cherry red and allow to cool then it bends more easily ?.
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On 07/08/2017 12:13, Andrew wrote:

Yup annealing it will make it easier to bend... although it slows down the whole process.
--
Cheers,

John.
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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.
Owain
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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 to Speedfit.
Observations: 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 sytem work.
Charles F
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On 8/5/2017 6:02 PM, Charles F wrote:

+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.
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On 05/08/2017 09:26, Tim Lamb wrote:

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.

--
Cheers,

John.
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