hot and cold water pipes in ventialed crawl space?? freezing risk

Lunielumps

Hi

My plumber needs to install new hot and cold water pipes to feed a kitchen in a new extension (Manchester, UK). The plumber has suggested the easiest way is to run about 8m of the pipes in the ventilated crawl space under our existing house before coming up beside the new kitchen. They'd be attached to the underside of the ground floor joists. 

There is another options of running them through the extension ceiling and cutting channels into block work to drop them behind appliances, but the plumber wants to avoid this. 

Our concern is that there would be a risk of these pipes freezing over winter, as this crawl space is very well ventilated with lots of air bricks. 

1. Are mains water pipes at signififcant risk of freezing if it gets cold enough over winter and they are in a ventilated crawl space? even with some pipe lagging?
2. what type of insulation would be needed to remove this risk?

Thanks

gefnew

Will pipe insulation stop pipes from freezing? - Plumbing Superstore Help & Advice

WIAWSNB

If they run the pipes in continuous lengths of 'poly' pipe - ie, not copper, and no fittings - and also add insulation, the chances of suffering a burst is very remote. 

Rodders53

WIAWSNB said:

If they run the pipes in continuous lengths of 'poly' pipe - ie, not copper, and no fittings - and also add insulation, the chances of suffering a burst is very remote. 

OP.  Ensure the underfloor area is thoroughly rodent-proofed if you go this route.  They just love gnawing on that plastic pipe and use the insulation for nest building.  (Whether pipes are under floor or in ceiling voids and they get access).

FreeBear

Lunielumps said: There is another options of running them through the extension ceiling and cutting channels into block work to drop them behind appliances, but the plumber wants to avoid this.

If you can avoid notching joists and ensure any copper pipes are protected from cement/plaster, running through the ceiling void would work. The pipes would still need to be insulated, but the heat loss would be lower and would contribute to heating the room (all be it by an insignificant amount).

For vertical drops in the wall, 20mm plastic conduit is the perfect size for sleeving 15mm copper. Fit a 35mm socket backbox where the pipes exit the wall, and you can end up with a very neat job. Ideally, the pipes need to be protected by a steel capping (preferably stainless steel) - Won't stop anyone drilling a hole through the pipes, but will make the task a little more difficult. Downside to running a cold water pipe in the wall is it will attract a little bit of condensation, although the heat from a hot water pipe will offset this.

If running the pipes under the floor, you can get various thicknesses of insulation. The standard foam pipe lagging from B&Q (et al) is only about 10mm thick. No where near thick enough in an unheated space. Fortunately, Rockwool, Kingspan, and others do pipe lagging up to 60mm (maybe more). Costs a bit more, but worth it.

Lunielumps

Thanks all, very helpful info! it will be one continuous stretch of plastic pipe and we've specced phenolic lagging. 

WIAWSNB

You should be fine.