Vent Pipe.

[sally123]

Hi, Could someone please help me. The original vent section of he soil pipe ha been cut off and replaced with a bossed pipe. connected to this is a 50mm waste pipe from the basin and bath into the soil stack. This 50mm pipe also serves as the vent pipe for the system, going up the wall and past the roof.
I have been told that the vent pipe should be at least 75mm. The chap that did it says it only has to be 50mm as it only vents the drain. Is he having me on?? Many Thanks.

 

[Simon F]

http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_H_2010.pdf
page 11 section 1.32

the vent pipe can be 75mm minimum,
but as 75mm pipe cost twice as much as standard 4" waste pipe it is usually done in that