Another water supply question

[Roger Hayter]

My current water supply goes through the stone wall diagonally from 60 cm below ground outside to near floor level inside. It is 20mm MDPE, in a 20mm drilled hole. Will my plumber protest if I put in a 25mm MDPE pipe the same way? I presume the requirement for ducting is to reduce the possibility of "hidden" water loss, but it would be really inconvenient to dig up the floor. (Under a full cupboard that would need emptying and removing, in a narrow space between an oil boiler, two walls and the oil supply pipe.) Indeed, If I have to dig up the floor it would probably be somewhere else. Did I mention that the rest of the floor is quarry tiles that may well be bedded directly on subsoil?

Is it reasonable to just drill another 25mm diagonal hole?

[harryagain]

I can't make any sense out of your post. It's normal to duct any service through a wall or to permit withdrawal and replacement where it would be difficult. Or for protection against damage, mechanical or frost.

Only with gas pipes have you to watch out, there are stringent rules governing gas pipe routes.

[Roger Hayter]

The question, such as it is, is how bad it would be just to drill hole through the wall the same size as the pipe and pass it through. This appears to be what was done in most old houses, and you usually see the service pipe embedded in the concrete floor.

[charles]

That used to be done with steel/iron pipes but nowadays an oversize hole is normal to cope with expansion and consequent pipe movement

[Roger Hayter]

What do you reckon the minimum duct size should be for a 25mm MDPE pipe?

42mm, 50mm, 68mm, 83mm? Those are the sizes I can think of that are readily available.

[Tim Watts]

Whatever it fits though :) Probably 42mm if that's not too big a hole :) I used 50mm though my floor to meet some 110mm that takes it in a smooth bend under the wall and out the side 2' below ground, but that has loads of slop. 42mm will probably be loose. Might even manage with 32mm but it could be a tad tight depending on how sharply you need to form bends.

My only other comment is:

Diagonal drilling sounds fine but I would angle it so it comes out >18" below ground so it's fairly well protected from frost by either the wall or the ground.

[Roger Hayter]

Thanks, thats reassurring. I may well end up with a 28mm hole and poythene tape round the pipe. BTW, 45 degrees gets me 2' below ground!

[GB]

I know what size a 28mm hole is, but I'm less sure what the outside diameter of a 25mm pipe is? Is the 25mm the inside diameter or the outside one? Either way, 3mm is not a lot of clearance.

[Roger Hayter]

When I were a lad, pipes were described by the Imperial insided diameter, and presumably if we get rid of the common market we can go back to this. But AFAIK all metric pipes are described by their outside diameter.

[GB]

That's good to know, thanks. :)

So, you know what size hole it needs, but not how much water it will deliver. There's progress, I guess.

With a standard masonry drill, it's easy to enlarge the hole by just using a larger drill. Does that work with a core cutter drill, or do you have to get it right first time?

[Roger Hayter]

FSVO easy, When drilling through a wall made of irregular, flattish slate stones the risk of the drill binding between two of them, and one's arms being turned into a twisted pair as in the Beano is quite high!

I am no kind of expert, but both in terms of accidentally slipping into the old hole and of not having a useable pilot hole I suspect it is best to get it right first time. There is no obvious advantage of progressive core drill holes, except perhaps making the cores lighter and easier to remove.