Hi everyone,
Need help with something called a "stack vent" or "stack vent pipe". In my 20-year-old, single-storey terrace house, it's a big ass pipe that comes up from the bathroom floor and goes up into the roof. I'm redoing the bathroom and the (young!) contractor says I don't need that pipe, it's old fashioned, we can get rid of it. But Google seems to say it's important! For venting gasses from the connected sewage system, as far as I can gather. Any experts who can advice me, please?

Many thanks in advance!

SuziQ

Hi there, i am a M&E consultant, vent pipe is necessary to vent out smells from water closet and floor traps (and manhole if applicable).

We are still using it for sanitary plumbing design (e.g landed property or high rise) hence from what i can tell, your contractor did not know what he is doing. The white cowl at every unit roof top is visible (normally above toilet room), you should be able to know if it is outdated

You need to have 50mm UPVC horizontal vent pipe connecting floors trap and water closet and then linked to a 75mm UPVC riser. The riser will go to the rooftop at 900mm height above roof level c/w UPVC vent cowl.

That's all.

As long as you shit in your home, you need it.

Actually 75mm is not just a vent pipe. It is a sewage pipe. It is straight connect to your main hole and many branch out to toilet and sink.

Nope. It is actual the sewage pipe. Very easily see. Check your vertical pipe in the toilet where it go up. Than go outside and see the roof vent pipe location.

Now that i know it is single storey. my bad  .

Yes it is seperate pipe. Normally soil (WC) and waste (floor trap, sinks, kitchen) combined in one pipe (Soil and Waste Pipe) while vent pipe is another pipe. Soil and Waste pipe should be 150mm (no matter is single or double) to avoid choke up in the pipe (e.g. sanitary pad...). Vent pipe varies because there is no fluid running inside so i would suggest 50mm for single and 75mm for double.

In OP case, the vent pipe should be connected directly from manhole and rise to roof top. No connection needed for WC and floor trap.

It also depend, if you have few of this vent pipe, you dont need to be 75mm,  50mm or less is ok. I have one in front for my master bedroom toilet, is small, maybe 1+", and the back is 2".

And yes is a must to have, if not you hear lots of blub blub sound when flush

Soil and waste pipe is from the kitchen (sink and floor trap). That is direct to Main hole and no vent. It is correct.

Bathroom sink, floor trap and wc is to sewage pipe 75mm. The vertical sewage pipe go down is to main hole and up to roof is to vent.

This is from what I explore in my home. Include checking inside the main hole.

Sure lah. New house don't have anything 1. And it fascinated me to see inside.

But warn you. Don't simply open it, if many many yrs. Bad experience for me. 

Wow, so many thoughtful replies! Thanks, everyone. I'll post some pics (if I ever figure out how to do that -- old-age newbie here) in case anyone's interested. And now I'm VERY worried about my contractor!!!! If he doesn't know this is necessary, what else does he NOT know???!!! Aiyoh. And too late to change. Sigh. Wish me luck with my renovation, please, folks, looks like I'm gonna need a lot of it....