Gas and water main in same pipe?

[Odyssy]

Kitchen rebuild in 1920 semi - kitchen floor is solid, rest of ground floor is suspended with 3 foot void below. Current water main is lead and was shared with neighbour, actual route of water main unknown (but under solid floor). Gas main (15mm) routing is currently a nightmare - up,down, all around - total of 7 elbows. Siting of new boiler and cooker are still undecided, so I'm trying to cover all possibilities in terms of routing of pipes and cables

I've lifted the old quarry tiles in the kitchen prior to laying new slate floor, and it struck me that while floor is up I could cut a channel in the cement screed and embed a 4" plastic pipe from the site of the existing rising main to the void under the dining room to accommodate a new 22mm gas main and a 25mm plastic water main which could be installed at a later date with no disruption of the new floor.
This would provide much more direct routing of both water and gas to the correct side of the kitchen and also provide possible access for 'return leg' of new electric ring main.

Are there any reasons/regs that this is not a good idea?

 

[breezer]

imo, its too shallow for one thing, and the gas man would probably refuse to do it if pipe being used for something else also

 

[Bahco]

While the floor is up get a Corgi to run you a new gas supply to your desired location.
You cannot run water pipe next to it or electric cable as there are minimum distances.
Change your water main from lead to plastic while you are at it.

 

[ChrisR]

Min distance is 25mm for gas to elec but I don't remember there being one for water. ANyone care to look it up?!

 

[PEDANTICVINDICTIVEMAN]

Why would there be a regulation distance to water pipes when all you do is bond them together at the earthing stage anyway, the only thing I can see possibly being a problem is the gas pipe would be in an unventilated duct, yes you would have to be carefull of the electric acable distance.

 

[Bahco]

Looking at my college notes there are reg distances for service pipes buried outside in roads and drives etc.
Apparently the gas main has to 200 mm from electric cable and have a radius of 350mm between it and the water main.
I assume they are for a reason and so it is not advisable to run gas and water together