I want to run a mains water pipe under my floorboards to feed an outside tap. There is about 12" of space under the floor, and I can get to both ends - there is an existing pull-through.
I was thinking of using plastic pipe, but wasn't sure about how to insulate it. Any suggestions on this, and what sort of pipe?
What distance do you need to cover? The problem is going to be supporting the pipe if it is a long distance and you only have access to the ends. I'm not sure of the official recommendations, but I would want to support a copper pipe at about 1 metre intervals, and a plastic one at smaller intervals than this. Can you take up a floorboard every now and then to achieve this - or just one long one if the pipe is parallel with the boards? You should then be able to fix it to the joists are regular intervals and also slide insulating sleeves (similar to Screwfix 10943 - but you won't need a whole pack!) over it.
If using plastic pipe, I assume you would use Hep2O rather than blue MDPE - which is intended to be buried in the ground.
I recently had lead water supply pipe replaced with plastic. It was simply laid (ground floor) under the floorboards on the packed earth. The regulations did not require insulation under the floor. However they were insistent on insulated ducting when passing through the walls. It is (they say) imperative to duct otherwise movement of the pipe with water flow will cause chafing and eventual failure.
I had a similar problem in our kitchen for extra hot/cold feeds to a small extra sink. I made up two Hep2o 15mm pipes with foam insulation (Wickes better type I think), with all joints taped well, and both taped together as a pair. The whole assembly was pulled under the floor as per a cable, and made off at both ends. They are currently lying on the concrete oversite slab, under a suspended floor. This was two years and two winters ago, and have been fine to date. I am not aware of any requirements to fix Hep2o, and Heps notes suggest such limited fixings as cable ties, if lying on a flat board surface.
Charles F
Use Hep2O, the non-barrier type because its more flexible. Jewsons sell it in handy 6m lengths for around £6 or 25m reel if you need more. AFAIK there is no need to insulate this pipe, and there hasn't been any problem with the one I fitted.
It should be insulated to minimize heat gains from warm air or from near-by hot pipes, and also to minimze surface condensation. You could put preformed lengths of insulation over the pipe before pulling it into the floor void, so avoiding taping or sticking the joint.
The main disadvantage of plastic pipe is that mice are liable to gnaw it to sharpen their incisors. It could be a problem if you ever get an infestation in the floor void.
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