I think the code says that you need to size a vent at one half the diameter of the largest waste pipe. But I seem to recall somewhere that said a minimum vent through the roof was 3 inches.

Hi Rod...

All houses must, at a minimum, have one 3" vent that penetrates the roof. The minimum vent through a roof, however, is 2".

The minimum vent required for all water closets, whether 3" or 4" pipe is 2"... so here, the 1/2 diameter rule doesn't apply.

Let me know if you have more questions...

MARK

Hi Rod...

All houses must, at a minimum, have one 3" vent that penetrates the roof. The minimum vent through a roof, however, is 2".

The minimum vent required for all water closets, whether 3" or 4" pipe is 2"...so here, the 1/2 diameter rule doesn't apply.

Let me know if you have more questions...

MARK

What about commercial installation using flush valve water closets? Same rule?

Same rule... 2" vent required for all toilets!

Awesome, thanks.

They may be combined... and what you see is 3" or 4" vent end piece that penetrates roof. This is more likely in warehouse-type installations where you have several toilets next to each other...

I think the code says that you need to size a vent at one half the diameter of the largest waste pipe. But I seem to recall somewhere that said a minimum vent thru the roof was 3 inches.

My Code requires one thre inch vent per dwelling, (we put ours in the kitchen) and a 2" vent for every fixture that has a trap with the exception of floor drains.Regards, Tom

Hi
In British Columbia every building must have one 3" vent.. also any water closet must have min. 1.5" vent and 2" wet vent...and floor drains 3" and larger can vent themselves.