[RodButler]

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.

[massplumber2008]

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

[RodButler]

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?

[massplumber2008]

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

[RodButler]

Awesome, thanks.

[Milo Dolezal]

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...

[speedball1]

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

[PlumbRob7]

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.