Manifold Water distribution using 16mm

[Inchbyinch]

Hi All,

More questions I'm afraid. I'm going down the route of a manifold water distribution system. I'm using the 16mm PERT-a_Pert pipe as I'm running the pipe in the concrete passive slab and it will withstand a bit more abuse when going in. Also it was recommended by the supplier as being better.

I'm presuming that I will need to use a 16->15mm reducer every where I connect on to bathroom fittings etc. as almost all fittings I'm looking at buying have 15mm connectors.

Thoughts appreciated. Feel free to question my sanity as I'm doing it quite a bit myself these days anyway

Thanks,

Ed

 

[Nickfromwales]

Pert 15mm pipe is available.

[Jeremy Harris]

Mine is all in 15mm, with 15mm manifolds.  Easy enough to get an all 15mm system and it makes converting to copper for any exposed runs easy (it's nice to have copper where any pipe is exposed, as plastic pipe always looks untidy, IMHO).

No need for barrier pipe for water, either, barrier pipe (i.e.the stuff with a metallised layer to reduce oxygen migration) is only required for sealed systems where you need to keep oxygen out of the water.  Oxygen is a good thing in supply water as it prevents the growth of anaerobic bacteria.

[Nickfromwales]

I did one job in 16mm and I used it for all the hot, hot return, and cold runs. I used this as I had a lot of off cuts plus a couple of coils over and wanted to use them up. 

I doubt if I'd use this by design tbh but any push fit pipe will need converting to copper where it terminates, but I wouldn't want to have to source 16mm manifolds for hot and cold tbh. 15mn is the standardised size so I'd try and stick to it where possible ( so you don't have to keep converting sizes where required ). Much easier to stick to one discipline imho. 

[Inchbyinch]

Thanks again, 

I've run the Hot and cold downstairs in the 16mm already so I'll prob have to stick with it now but looks like I'll have to buy a load of reducers and they are not cheap. 

TBH I was given a bum steer by my supplier, he recommended the 16mm as a better product and better for manifolding (his manifold).

Ah well if I knew it all I'd be a plumber, and I'm not. ?

Thanks again for the replies, i take it then it's not the end of the world but probably a headache or two.

[ProDave]

I will be doing the same, 16mm leftover bits of UFH pipe from the last house, using the 16 to 16mm adapters at each end. The flexible pipe will wind its way through the posi joists, converting back to copper in some accessible point for the final conections. I don't want any hidden joints.

I doubt I will actually use a true manifold. The objective will be the absolute shortest possibler route from hot tank to hot taps, and I doubt that will be achieved with a manifold, rather just branches off a backbone pipe with individual isolators.

For the long run to the kitchen tap, I am going to install a parallel 10mm pipe. Only when I try it will I find out if the 10mm pipe delivers enough hot water flow to the kitchen tap. If it works, that's a lot of wasted volume saved. If not the 16mm pipe will be there to swap over.

[Nickfromwales]

If you have good cold mains pressure ( or have installed measures to provide it ) then you'll be surprised at how good the flow is through 10mm pipe. 

If your using JG Speedfit then the likelihood is you'll add more restriction as their Superseal inserts are ridiculously bulky compared to the Hepworth stainless insert which is exremely thin / low profile, plus it's nigh on full internal bore ( the size of the original pipe prior to inserting it ). 

Hepworth all the way for me. 

[Nickfromwales]

Connect some to your outside tap dave and give it a test drive . 

[ProDave]

I must admit I was thinking copper for the 10mm run, no restrictions at joints (soldered)

High mains pressure so I expect the hot water to be running at 3 bar from the PRV.

[Nickfromwales]

That's good news. I'd second going for copper. 

[Nickfromwales]

Oh, and just remember that if you over solder an elbow, the solder will flow inside the pipe and can partially fill it if there's a sump ( eg the elbow is at the bottom of a vertical drop and the weight of the pipe is pushing down on the elbow ) if you get what I mean. 

[Nickfromwales]

1 hour ago, Inchbyinch said:

Thanks again, 

I've run the Hot and cold downstairs in the 16mm already so I'll prob have to stick with it now but looks like I'll have to buy a load of reducers and they are not cheap. 

TBH I was given a bum steer by my supplier, he recommended the 16mm as a better product and better for manifolding (his manifold).

Ah well if I knew it all I'd be a plumber, and I'm not. ?

Thanks again for the replies, i take it then it's not the end of the world but probably a headache or two.

Don't beat yourself up. This is VERY robust pipe and is imo belt n braces. The connectors that affix to the pipe are also extremely good in comparison to a regular compression or push fit coupler, so you'll have a very good install at the end. . 

I would use it again in a heartbeat, and would favour it over regular push fit.  

[ProDave]

My thinking is I need 10mm copper for the LPG supply to the hob (can't do that in speedfit) so one coil of 10mm copper will probably do my LPG run and my kitchen hot water run.

[Inchbyinch]

Thanks Nick, 

as ever a wealth of information. 

Ed

[Nickfromwales]

And the benefit is that the fittings go around a copper pipe with no strangulation of the internal bore, whatsoever

 

[Jeremy Harris]

A word of caution.  I tried to run 10mm copper pipe (still have a big coil of it here) to our kitchen hot and cold feeds.  There was no way whatsoever that I could feed it through Posijoist.  The pipe snagged very badly on the Posijoist metal plates and try as I might I could not get it to feed off the coil cleanly.  I ended up damaging two runs of 10mm copper then gave up and went and bought a roll of 15mm plastic.  The plastic doesn't snag at all, I found.

Admittedly part of the problem was me working on my own, but even with two I think it would have been a difficult job, as just the weight of the pipe after a few metres is enough to make it sag and then catch on the metal edges.

Afterwards I did realise that if I'd put in some cheap 15mm plastic pipe I could probably have fed the 10mm copper through that to avoid the snagging problem.  You may be able to arrange runs where this isn't an issue, but for me there was no easy way out of running all the pipes between the floors.

[Nickfromwales]

Using two guys to pull 10mm copper is essential. If I'm on my own I'll do long runs with pulled bends on the end and use straight sockets to join onto the next straight run. 

Based on your comment J, a valid additional point can be raised. That's that the posi joist metal webs will slice through push fit / plastic if left against them. Pipes move a little with water hammer / movement so be aware of this risk and take measures to prevent such occurrences.   

[Jeremy Harris]

I did wonder about this, so decided to fix all my pipes down with dual pipe clips at every joist, to keep them clear of the metal webs. 

As an aside, I first fitted some 22mm pipe clips (the clip over ones) along the run and then fed the 15mm pipe through them.  This meant that I could feed the 15mm plastic pipe single-handedly using the 22mm clips as guides to keep it off the metal webs, then just unclip the pipe clips and swap the pipe over to the adjacent dual clips.

[Nickfromwales]

"Adapt and overcome"

[Gone West]

2 hours ago, Nickfromwales said:

 

Hepworth all the way for me. 

 

I first used Hepworth Hep2O in around 1994 after seeing it at a self build show. I thought it would make replumbing my house much easier than using copper. Everything went ok even if the fittings were a bit clumsy. After a few years a radiator rusted through and I thought I must have used the wrong amount of inhibitor so flushed the system and put in new inhibitor. Then another radiator rusted and I started looking for other reasons and discovered that Hepworth hadn't used a barrier in the pipe. After contacting them I was told they now produced a barrier pipe and I should replace the old pipe with new at my cost. So after telling them what I thought of them I did replace the whole system but with Speedfit and never had any problems. I never go back to using something that caused me problems in the past, even if they have improved.

[ProDave]

Most of my run to the kitchen hot tap will be parallel with, not through, the posi joists, so I should be okay.

[Nickfromwales]

58 minutes ago, PeterStarck said:

I first used Hepworth Hep2O in around 1994 after seeing it at a self build show. I thought it would make replumbing my house much easier than using copper. Everything went ok even if the fittings were a bit clumsy. After a few years a radiator rusted through and I thought I must have used the wrong amount of inhibitor so flushed the system and put in new inhibitor. Then another radiator rusted and I started looking for other reasons and discovered that Hepworth hadn't used a barrier in the pipe. After contacting them I was told they now produced a barrier pipe and I should replace the old pipe with new at my cost. So after telling them what I thought of them I did replace the whole system but with Speedfit and never had any problems. I never go back to using something that caused me problems in the past, even if they have improved.

Blunt as this may sound, it's down to each individual to make sure what they're buying is fit for purpose. 

I can't shout at the greengrocer for giving me apples when I should have asked for oranges . 

[Jeremy Harris]

To be fair, the problem of oxygen migration through plastic pipes wasn't a well understood one back in 1994.  Barrier pipe is a relatively new invention (in this application) and the manufacturers didn't fully understand how big a problem oxygen migration through plastic pipe was.  There was a school of thought that believed that the reducing capacity of inhibitors would be good enough to prevent water in sealed heating systems from developing a high enough ORP to cause corrosion problems.

We now know that some types of plastic pipe can be far more oxygen-permeable than was originally thought, so those for heating systems now include some form of oxygen barrier, either a thin lamination of aluminium or a lamination of oxygen impermeable plastic.

If Hepworth had been asked specifically to give the oxygen permeability of their plastic pipe 20 years ago they may well not have had proper data, as I have a feeling that it was only when problems were encountered in heating systems plumbed with the stuff that the manufacturers took heed and realised they needed to come up with a fix.  In many ways it's like push-fit pipe fittings.  When these first came out they quickly developed a reputation for being less than perfectly reliable.  Those we use today seem to be at least as reliable as a conventional pipe joint, as the manufacturers have tweaked the designs and made them easier to fit correctly.

[Gone West]

29 minutes ago, Nickfromwales said:

Blunt as this may sound, it's down to each individual to make sure what they're buying is fit for purpose. 

I can't shout at the greengrocer for giving me apples when I should have asked for oranges . 

It's also down to the manufacturer to produce something fit for purpose. If you have to test everything you buy before using, it will slow down work ridiculously.

Have you gone back five or six years later to check the stainless steel inserts. Do you know what grade of stainless steel they are?

[Jeremy Harris]

11 minutes ago, PeterStarck said:

It's also down to the manufacturer to produce something fit for purpose. If you have to test everything you buy before using, it will slow down work ridiculously.

Have you gone back five or six years later to check the stainless steel inserts. Do you know what grade of stainless steel they are?

You're right, but sadly there are an awful lot of products that are released to the market with flaws, flaws that often only become apparent years later.  Most manufacturers will do some form of accelerated life testing, but this is far from being a perfect way of predicting how a product may perform years later, because some things are just very difficult to assess. 

I had a look through the testing that some of the materials we've used underwent, particularly the roofing as I was concerned about it fading or going brittle with age.  The manufacturer tries to simulate ageing by subjecting it to high UV levels and many rapid heating and cooling cycles but I doubt that they are wholly representative, as my guess is that the slow migration of plasticisers may not be speeded up by this sort of accelerated life testing.

I think we all run the risk of being product testers for any relatively new product, whether we like it or not.  Even car manufacturers get it wrong with monotonous regularity; all three of the cars I've owned in the past 11 years have been subject to recalls to correct defects only found years after they went in to production, with two of those being safety critical (one was a steering joint that had to be replaced, the other was a fault with the accelerator sensor).  Only one was a minor problem, fixed with a new firmware download, rather than any physical work.