A few questions including the obligatory plastic vs copper

[Crofter]

I'm reaching the stage where my vague ideas of where to put pipes ('over there somewhere') has to translate into actual plans and decisions.

In my infinite* wisdom, I have already laid the floor and had just assumed that all the 15mm water pipes could run in the 25mm service cavity. Now that the wiring is going in, the remaining space is looking tight at certain points.

 

I'm tempted to use plastic, at least in part, because I can reduce the number of fittings. And I've happily used it in the past. But the push-fit fittings are too bulky to hide within the service cavity, so can I just switch to copper for these? Or alternatively, seeing as all the fittings will be in cupboards, behind kitchen units etc, then just bring the plumbing out from behind the plasterboard.

 

It seems if you google long enough, you can find every opinion available on the pros and cons of plastic and copper, and whether to stick to one system throughout or mix and match (plastic with copper fittings). And then of course there are the different brands of plastic system. In the past I have merrily used whatever was available and never had a problem, but that was always small changes and this is a whole house (albeit a very small one).

 

 

A final question: the (TM) shower will be going on an external wall. Other than aesthetics, anything to consider? A concealed one would obviously look neater but require a bit of rework to make the space for it in the wall. Or I could bring the wall forward a bit with a plywood panel.

 

*this may include infinitely small

[Jeremy Harris]

I chose to use plastic solely because it meant having no fittings at all inside the service void.  I brought the plastic out through the plasterboard, almost always behind a cabinet, and then converted to copper for the connections to taps etc.  I didn't like the idea of having pipe joints inside a closed space, that would be difficult to access later.  With a 25mm deep service void I think the only thing to watch might be the depth of the pipe clamps.  I used the ones with the flip over top catch, that latches down tight, but they might be a tight squeeze in a 25mm deep void.  I don't have one to hand to measure, unfortunately, as I had a big clear out earlier this week and binned loads of boxes of stuff left over from the build.

[MikeSharp01]

23 minutes ago, Crofter said:

But the push-fit fittings are too bulky to hide within the service cavity, so can I just switch to copper for these?

Given that you find about equal support for both sides in the plastic / copper argument it is but a small step to conclude that both systems are valid (not sure what everybody heres favourite plumber @Nickfromwales view on it all is) as you can mix the two systems you perhaps are in the very best position. You will still need the converter fitting between the plastic and the copper to get into the gap - this can be brass but then you must use an insert for support against the olive and sealing (some inserts are just support others offer support and sealing). John Guest have a slip connector (not suitable for central heating) which is very slim so might be worth looking at that.

Edited April 14, 2017 by MikeSharp01
Added slip connector URL

[Jeremy Harris]

No need for any form of converter fitting I found.  The push-fit connectors work as well on copper as they do on plastic pipe of the same diameter, and as long as they are assembled correctly seem to be very reliable.

[MikeSharp01]

Sorry, yes should have used connector not converter they do work on unscratched copper tube very well.

[JanetE]

We used the hep20 on recommendation from here.

I Iaid all the pipe and connected up, really easy to use and so convenient. We have a manifold system no hidden connections and as Jeremy says it's really easy to connect up copper to.

[asklair]

Copper for me, been a really mild winter, hundreds of mice (I do mean hundreds).

Showing my age, plastic pipes use to let air into your heating system, cut new pipes and you will see a circle in the pipe which is a membrane to stop air getting in.

I stand to be corrected in what I have said.

There are simple fittings for copper pipes now, someone with more knowledge could give advice on them.

 

[Jeremy Harris]

Mice would find it pretty hard to get into an airtight and pressure tested house, I think.  About the biggest air leaks we had were through five keyholes.

 

It depends a great deal on where pipes run, though, and if I had pipes running through an area outside the sealed and insulated envelope, where the little blighters could possibly gain access, then I think I'd avoid using plastic pipe there too.  The problem then seems to be that the little blighters will just chew through all the pipe insulation.................

Edited April 14, 2017 by JSHarris

[Crofter]

9 minutes ago, asklair said:

Copper for me, been a really mild winter, hundreds of mice (I do mean hundreds).

Showing my age, plastic pipes use to let air into your heating system, cut new pipes and you will see a circle in the pipe which is a membrane to stop air getting in.

I stand to be corrected in what I have said.

There are simple fittings for copper pipes now, someone with more knowledge could give advice on them.

 

 

I did use push fit copper once, something about it seemed a bit too much like magic and somehow I trust a compression fitting more. Weird I know! So I'm not looking at plastic primarily from the persepctive of ease of use of the fittings, it is more to do with being able to 'cable' the pipe around awkward spaces.

[Jeremy Harris]

4 minutes ago, Crofter said:

 

I did use push fit copper once, something about it seemed a bit too much like magic and somehow I trust a compression fitting more. Weird I know! So I'm not looking at plastic primarily from the persepctive of ease of use of the fittings, it is more to do with being able to 'cable' the pipe around awkward spaces.

 

 

That sums up my feelings, too, as before this build I was very against the idea of using plastic.  Part of that was the stories I'd heard of failing push-fit fittings, but I'm sure that many of these were a consequence of the fitting not being correctly installed.  The main problem with push-fit is that it seems too easy, when the reality is that the depth to which the pipe has gone into the fitting has to be physically checked, to make sure it is fully home.  I found that relying on "feel" wasn't good enough, and that it was essential to put a Sharpie mark on the outside of the pipe at the correct insertion depth.  This depth was the same for all the fittings I used, so I made up a tool (a bit of bent aluminium) that could be put on the end of a cut pipe and used as a guide to mark the insertion depth.  From then on it was very quick and easy to check that fittings were properly installed, and I had no leaks at all from any of them.  The only slight leaks I had were from a couple of compression joints, both a consequence of them being in a very restricted area, where access was poor.

[Crofter]

It appears that Hep2O is the gold standard when it comes to plastic stuff. I've got quite high water pressure and will be using a UVC so don't want to cut any corners. But presumably the other makes, like JG or Floplast, are all approved and should be perfectly up to the job?

 

It would be interesting to hear if there any genuine reports of failure with the up to date versions of the cheaper systems.

[Rossek9]

I used JG speed fit when redoing a bathroom in our old house. Great stuff I found. Didn't have any leaks and also the speed fit pipe is marked so you know if the fitting is fully seated correctly.

 

Even replaced a few old weeping compression joints with the stuff and I have no complaints.

 

Very easy to use and having done a kitchen many years ago using copper and compression joints I would use the speedfit stuff again.

 

Heard of a few folk who have had issues with the cheaper grey coloured (not sure of brand) fittings though.

[Nickfromwales]

52 minutes ago, Crofter said:

I've got quite high water pressure and will be using a UVC so don't want to cut any corners.

Not a problem TBH, as with an UVC you'll need to fit a PRedV and have it set at 3-3.5bar max . Modern plastic is rated at 10bar cold so you'll only ever see less than half its max operating pressure. 

[Crofter]

38 minutes ago, Nickfromwales said:

Not a problem TBH, as with an UVC you'll need to fit a PRedV and have it set at 3-3.5bar max . Modern plastic is rated at 10bar cold so you'll only ever see less than half its max operating pressure. 

 

Ah but the cold system would not have a PRV... would it...?

Mind you a quick peek at Google suggests I'm about 30m lower than the tank, so that makes three bar, I think. So sounds like a reasonable margin for safety.

[Jeremy Harris]

Normally you have the PRedV on the incoming cold supply, so that both the hot and cold supplies run at the same pressure.  Doing it this way makes life easier for things like mixer taps and thermostatic shower mixer valves.

Edited April 14, 2017 by JSHarris

[Nickfromwales]

JG SPEEDFIT has inherent flaws imo. 

Firstly it's not a single action install. You have to loosen the 'nut' to free up the moving parts inside, then, after inserting the pipe ( with insert fitted ) you then must fully re-tighten the nut to grip the pipe. 

After that, you need to then fit a separate plastic circlip between the nut and the ring to stop the fitting from accidentally being released and failing catastrophically. 

Now with Hepworth, 

Cut pipe

Push in the ( much thinner ) insert. 

Push pipe in. 

Drink beer. 

 

Theyre chalk and cheese. 

[Nickfromwales]

7 minutes ago, JSHarris said:

Normally you have the PRedV on the incoming cold supply, so that both the hot and cold supplies run at the same pressure.  Doing it this way makes life easier for things like mixer taps and thermostatic shower mixer valves.

Yup. 

Unfortunately G3 requires the PRedV ( multiblock aka control group ) to be mounted at the UVC location ( iirc within 500mm of the cold inlet for some MI's ). 

Therfore you have to take a balanced cold feed, tapped off said block, back to any mixer outlets upstream. 

I combat this by doing what J suggests above, but for G3 you MUST have the manufacturer supplied PRedV at the UVC as it also incorporates a 5 or 6 bar cold mains PRV to mitigate against the PRedV failing. 

Regs folks, wonderful regs. 

Fwiw, @Crofter can easily choose between either discipline as his hut is quite small

[Crofter]

Ah now that is useful info!

I had been planning a simple system of a hot and cold run, everything just teeing off the cold- including the shower, which is the only mixer.

I could run a second dedicated pipe run for the shower, tapped off the PRV- perhaps this is a good idea anyway?

 

Any thoughts on leaving space for the shower unit, by the way?

[Nickfromwales]

Re the shower. Just fit a surface mounted bar mixer. 

Any one that uses standard 150mm centres, so changing it is a 5 minute job ( and change of £100 ). ?

Keep remembering "it's a renter, it's a renter" . 

[Nickfromwales]

Perfectly good for a couple of quid more. 

[bassanclan]

If like me you haven't quite come over to plastic pipe yet, Wickes have a nice offer on copper tube 3for2 and then 15% off this weekend. It is only in 2m lengths, but it's still a good price.

[Crofter]

So this whole balanced feed thing...

Does the mixer shower need a dedicated cold supply? I hadn't realised or planned for that- it will be much easier to have the single cold feed as planned, so the WC and basin would tee off it. Will this cause problems?

[RichS]

7 minutes ago, Crofter said:

So this whole balanced feed thing...

Does the mixer shower need a dedicated cold supply? I hadn't realised or planned for that- it will be much easier to have the single cold feed as planned, so the WC and basin would tee off it. Will this cause problems?

 

It will if someone flushes the loo while you're having a shower.

[PeterW]

Shower feed in either 15 or 22mm, basin and WC fed in 10mm separately. 

 

There is some logic in feeding all the WCs and outside taps off the cold before it hits the PReV so that when you lose the cold pressure from a loo flush you lose both hot and cold pressure. 

 

I may put a separate feed in with a second PReV set at say 1.5bar to feed the WC and outside taps. Longer term that will be fed from rainwater all being well - means it's installed once as a separate circuit and no retrofit needed. 

[Triassic]

13 hours ago, RichS said:

 

It will if someone flushes the loo while you're having a shower.

Where you flush the loo or turn on a bathroom tap in our soon to be demolished house to shower slows to a dribble!