Pipes through brick walls

[handyfella]

I have looked at masonary drills to drill a hole for a 15mm water pipe.
the hole needs to go through a cavity wall.
is there any way of eliminating/reducing the "exit wound" on the inside of the bricks?

secondly, the waste pipe for the kitchen sink has black mould forming in a ring around it on the inside wall. (there is no leakage) a plumber said it;s normal and nothing can be done. is that right or is he talking rubbish?
the old toilet had an overflow pipe through the wall and had the same problem

 

[Richard C]

I have looked at masonary drills to drill a hole for a 15mm water pipe.
the hole needs to go through a cavity wall.
is there any way of eliminating/reducing the "exit wound" on the inside of the bricks?

I always use an 6mm pilot to drill right through the wall first as this causes minimal damage on exit; then take your 18mm drill & drill through into the cavity from each side; or if access is difficult, you can minimise damage by taking it very slowly as you break through.

secondly, the waste pipe for the kitchen sink has black mould forming in a ring around it on the inside wall. (there is no leakage) a plumber said it;s normal and nothing can be done. is that right or is he talking rubbish?
the old toilet had an overflow pipe through the wall and had the same problem

Sounds like a load of Cr*P to me! If you don’t have a leak, damp is getting through from the outside, make sure the waste pipe is sealed internally & externally & it slopes down towards the outside wall.

 

[handyfella]

many thanks Richard!

 

[JohnD]

it might also be condensation forming on a cold pipe, if the room is damp or humid.