pipes in the floor

24 Apr 2012
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United Kingdom
hi folks
I have to run in a hot and cold feed to the island in my new extension before the concrete floor gets poured.
I was going to use speedfit pipe run inside a plastic duct.
my question is should it be 22mm because its about 7 metres of run or is 15 mm fine for that.,

also any special protection as it will be eventually encased in 100mm concrete.
should I insulate the pipes inside in the duct as its being laid on the sub floor before insulation and underfloor heating piping goes down ?


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The decision on whether to use 22mm or 15mm is down to design calcs and pipe sizing. It will be based on loading units, resistance and flow rates.
Without knowing this info, impossible to say for sure.
As above the size of supply is dependant on a number of factors, so a bit more info would be useful.

I did I similar job recently with H & C in screed to an island. I used Hep2o Pipe in Pipe system. This is Hep2o pipe inside a flexible conduit, this allows for a continuous (no joints) run of pipe to be installed that can be removed and replaced, if required, without disturbing the floor.

They also do a range of termination fittings for use with the conduit system. See their installer guide.

Also if installing in screed keep the Hot and Cold pipes a minimum of 50mm apart to prevent the hot pipe warming the cold supply.

As you are installing UFH into the screed, you will need to think about your route for the cold water and also insulate it as the UFH will heat the screed up and transfer that heat to your cold water supply.

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