Changing from copper to plastic

[JohnH]

Hiya all

First of all I am hoping that the 2 day power failure in the Kent area here hasn’t caused my Navitron solar manifold to overheat too much, luckily the weather was overcast.
I am slowly changing the entire pipework in my DHW from copper to Polyplumb plastic. The CH is already plumbed in 10mm plastic and works fine. The pipe run in 28mm from the cylinder will connect to a manifold to supply hot water in 15mm to the kitchen and downstairs toilet, etc. The kitchen has been gutted and at present the floor has been dug out to a depth of 30cms to make way for an insulated concrete floor. I want to lay insulated plastic pipe in the screed for the hot supply pipe (and cold?) to the sink and washing machine. However, I am having trouble sourcing pipe ductwork that will fit taking into account no joints are allowed under the screed. The normal method is the use 15mm flexible conduit pipe then screed over the top but then there is no room for the insulation. Has anyone got any ideas? What about using plastic down pipe with bends?

JohnH

[Richard Owen]

Plastic pipe (unlike copper) doesn't need to sit in conduit in screed. If it did, UFH wouldn't work very well.

Can't you just lay the pipe?

Or haven't I understood what you are trying to do?

[KLD]

John, can you be a little more specific what your new floor structure will be? Do you propose: hardcore - blinding - damp proof membrane - insulation - concrete, or is it hardcore - blinding - membrane - concrete - insulation - screed?

I do understand that the building regulations require a conduit for any pipe covered under concrete. That said, UFH pipes don't follow that prescribed pattern either. So, if you were to do away with the conduit  you could bury the pipe in the insulation layer, and then screed over. Works a treat.

Klaus

[Justme]

I still think the UFH is going to come back & bite a few people in the behind in the future.
Its still too soon to tell if all these "new" ways of doing it will work long term.

ALL pipes laid in concrete will get holes in the end.


Not only that but all the thermal expansion & contraction with no place to flex will add to the problems.

[KLD]

Well, only time will tell. And for me the glass is half full!
The OP didn't ask about UFH anyway, and the "bury pipe insulation" method has only very small contact areas between concrete and pipe, and for the "glass half empty" types these bits could be protected by a short length of conduit. UFH vendors also offer pipe formers for this area to make smaller radius bends.

Klaus

[JohnH]

Hi Richard

Thanks for your reply
Under Floor Heating? No, I am only supplying hot and cold water to the kitchen sink, toilet basin and any appliances. At present water in the pipe run from the solar tank to the kitchen tap takes between 40-50 seconds to get from cold to hot and I want to reduce this time. The original copper pipes that were buried in the wall in the mid seventies have caused damp and condensation. In the original concrete floor the 3” galvanised steel trunking housing the hot and cold supplies has rusted away and there are no leaks visible.

Klaus
I am not actually doing the building work as this is being done by a professional. However I have ordered this morning, 1 tonne bags of ballast, sharp sand, a membrane sheet and 8 x 4’ sheets of 2” insulation.  I have also got to replace the old lead mains riser with MDPE pipe.
I assume the cold water supply is laid on the sharp sand and covered over, then the membrane, insulation and then screed, is this correct?  I am not sure what the blinding is.

Thanks

John

[sleepybubble]

Sheath your barrier pipe with MDPE. i.e. for your 15mm services to sink etc in polyplumb, run them through some MDPE of suitable internal diameter as 'conduit'. No joints under the concrete obviously. If you do it right (no sharp bends) you call pull the pipes and change them if they do ever develop leaks in the future.

[dhaslam]

Wouldn't it make sense to run the pipe in the insulation layer?       

[KLD]

Wouldn't it make sense to run the pipe in the insulation layer?       

Yes, it does, as I mentioned above. I found it easiest to use a 1/2" router with a straight cutter bit about the size of the pipe. Route a channel, press the pipe in, use the dust produced to cover the pipe, tape with alu tape: done. And it works very well.
Also, I've used spare lengths of UFH pipe for this purpose. The Uponor Pex-Al-Pex keeps its shape when you bend it, so is easy to handle. It does need special inserts to connect into standard compression fittings. Let me know if you need a reference.

Klaus

[JohnH]

OK, The plumber assistant at B&Q informs me that the usual method is to lag the pipe with insulation then wrap Denso tape around the outside. Then lay the pipes in the channel and screed over. I wouldn't have thought this is ideal as I would prefer a channel or duct. I suppose it could be knocked up out of ply or OSB board but needs to be over 6 metres long.

JohnH

[tony.]

what aout 2 lengths of electrical trunking buried in a screed.

you get trunking designed to be used in a screeded floor, i have used it many times.

tony

[Richard Owen]

Denso tape? Inside?

Denso tape is used for excluding water from the system.

I think if I were burying a metal pipe in concrete outside I might go this route, but you aren't using metal and you aren't using concrete.

Sand and cement screed is a very different beast in terms of abrasion and impact damage on pipes.

I'd go with the channel in the insulation idea and if you want to put it in a conduit, use the mdpe pipe idea.

Keep it simple.

[dhaslam]

OK, The plumber assistant at B&Q informs me that the usual method is to lag the pipe with insulation then wrap Denso tape around the outside. Then lay the pipes in the channel and screed over. I wouldn't have thought this is ideal as I would prefer a channel or duct. I suppose it could be knocked up out of ply or OSB board but needs to be over 6 metres long.
JohnH

In my last house, which had radiators,  the pipes ran around the outer walls in a channel which was filled separately with a concrete mix containing a high percentage of sand.  It was just as well because there were two leaks in the copper piping.   

[JohnH]

Tony

I originally put lengths of 3" galvanised electical trunking in the floor back in 1983 but condensation has caused them to rust so I have taken them out. I will be using insulated plastic pipe and there is also an iron gas pipe as well.  I can only find 150 x 150mm square electrical trunking that will take all this and accommodate the radius bends but they are really too deep for the floor.

John

[sleepybubble]

Tony

I originally put lengths of 3" galvanised electical trunking in the floor back in 1983 but condensation has caused them to rust so I have taken them out. I will be using insulated plastic pipe and there is also an iron gas pipe as well.  I can only find 150 x 150mm square electrical trunking that will take all this and accommodate the radius bends but they are really too deep for the floor.

John

I saw some leaflet the other day about a national survey of commercial prpoerties, to indentify whether buried gas pipes exist on the property and what they were made of. I'm not gas certified so I may be wrong on this, but I got the impression that buried gas pipes can no longer be metal, but must be plastic now. Something to do with insepctions and corrosion and the like. All buried gas pipes that are metal on commercial porperties have to be replaced with either above ground metal installations or buried plastic. I wonder how long that moves over to the domestic market?