What size core drill to select All aspects of plumbing questions and answers, help, tips and information

[rdo1104]

Hi

This is my first time so apologies if this is posted to the wrong area!!

I am getting a new boiler installed and also have several other pipes to get through the walls. I'm unsure what core drill sizes to select for the following pipes:

100mm boiler flue
40mm washer waste
25mm boiler waste (condensing)

There seem to be a lot to choose from of similar sizes but I would like to know what clearance is needed for each. Many thanks :?

[htg engineer]

condensing boiler flues has to rise away from the boiler so this hole has to be larger than the flue 120 - 140mm i would say. The condensate and the washing machine pipe will not require any clearance, as they are plastic and will not corrode if in contact with bricks and mortar.

[rdo1104]

Thanks for that. Much appreciated