Central heating pipes in screed


Postby pugsman » Sun Apr 06, 2008 11:33 am

Help. I am having an extension built. I will require extensions to the current heating loops which are flow and return. What is the thinking on best practice for pipe layed in the screed? If i use copper what is the best method of protecting the pipes from the cement? What depth cover should they have. Or should i use plastic? if so what is the thinking/ best practice on the "T" joints? I am under the impression that compression fittings are a no no in screed floors so how does one accomodate this with plastic. My preference is copper as this is where my limited experience is. Any replies most welcome.
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Postby knowall » Mon Apr 07, 2008 11:32 am

The practice now is to use plastic pipes sleeved in another plastic called pipe in pipe with no joints or if you do want to have joints have them at a point under the radiator at least you will know the point where they are
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Postby knowall » Mon Apr 07, 2008 11:51 am

use plastic
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Postby chris_on_tour2002 » Mon Apr 07, 2008 8:38 pm

personally i'd go with copper, and definitely soldered joints over compression, or better, no joints at all - try bending the pipe instead of using joints to at least keep the unnecessary joints to a minimum. to protect the pipe from the cement just wrap it in Denzo tape, available from any plumbers merchant. its a bit mucky but it will do the job.
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Postby knowall » Tue Apr 08, 2008 4:45 pm

has the last contribution considered heat loss as he will have no insulation except that denso tape
please comment
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Postby pugsman » Wed Apr 09, 2008 7:30 am

Many thanks for the replies.
If i use plastic can i bury the compression joints for the "T"s, in the screed?
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Postby chris_on_tour2002 » Wed Apr 09, 2008 9:33 am

you can insert copper pipe-in-pipe also. if running 15mm insert it into 22mm first then wrap that in denzo tape. the air gap inside the larger pipe will be warmed up by the inner pipe when the system is running and will provide insulation. in addition the extra layer of copper will provide an additional layer of protection from cementous erosion. if running 22mm then do exactly the same, inserting into 28mm (if the channel allows). the combination of air, denzo and cement will be insulation enough. air does not conduct heat very well, ask any scuba diver that wears a drysuit in cold water. whilst air is not the most effective insulator it is still pretty good. the heat loss will be minimal.

you just need to give a little more thought to the joints, thats all.
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Postby knowall » Wed Apr 09, 2008 12:57 pm

Please note trying to insert 15 mm copper wrapped in denso into 20 mm pipe is impossible
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Postby chris_on_tour2002 » Wed Apr 09, 2008 4:18 pm

[quote] "Please note trying to insert 15 mm copper wrapped in denso into 20 mm pipe is impossible"


knowall,

thats not what i said - my exact words were "if running 15mm insert it into 22mm FIRST, then wrap that in denzo tape." only the 22mm need be wrapped, the 15mm would not require wrapping if it were inside another pipe already wrapped.

pugsman,

i would avoid the use of compression fittings anywhere where they cannot be accessed, especially if burying in screed or concrete.
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Postby pugsman » Thu Apr 10, 2008 8:53 pm

Basically my central heating pipes are in the floor in my house. They look like they were lagged with a fiberglass type material prior to burying. We have had an extension built and now it is time to plumb it. I do not want to fall fowl of building regs hence my questions. As the upstairs floors are in it will be a lot easier to plumb the upstairs using plastic for water and heating radiators from below as the ceiling is not yet in. Downstairs seems a bit of a puzzle. Idealy Iwould like to do this in copper, lag with denso and bury in the screed, leaving tails up where required for "onward" plumbing, again at a later date.
What is the general thinking on this, wanting to keep within current regs?
Bye the way
Builder is sulking because i will not use his plumber who in my opinion wants an absoloute fortune for what I believe is a weeks work, and I am very capable, consientious enough to want to follow regs, and bright enough to work out that £4000 for labour is a lot for a weeks work.
Finally, currently all of my cold taps are fed directly off the main. I would assume from what i have read that this would not meet current regs. Can I just fit check valves in the extension and keep mains pressure or do I need to take cold water from a storage tank?
Thanks for your replies again.
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Postby chris_on_tour2002 » Sun Apr 13, 2008 12:35 pm

what you plan to do, denso and tails sounds fine. and as far as i am aware there is no problem having all the cold taps running off the main. you must have a non return valve on any exterior taps such as a garden tap. and 4 grand for a weeks work is an absolute p*** take. tell him to take a leap! i assume that price would include all materials but even then you would expect to pay that sort of money to completely change a central heating system.
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Postby htg engineer » Sun Apr 13, 2008 7:11 pm

£4000 what a joke - good job you know a rip off when you see one. But you will get people that will pay it - like the vulnerable and the elderly where people take a lend.

If he was reported, trading standards would take an interest, people think they can just charge what they like. People have ended up in court for charging excessive amounts for labour.
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