Sink and Toilet Venting and Tie Ins

Hello Everyone,

I am new to the forum and have a question about a sink and toilet vent tie in.

I am doing all the rough work, but have a friend who is licensed, former union plumber now on his own, does great work and will be doing all the final plumbing. I have not bounced this off him yet as he has been busy, so wanted to post here to see if it can likely be done.

The bathroom I am adding is new, there is no vent stack, however close to where the drain will be going into the basement and into the sewer there is a large 4-5 inch (maybe larger diameter) vent that comes off the main sewer connection inside my basement that runs to the street and vents to another location outside the house.

Can I use this as a vent for the first floor bathroom? I would rather do this than run a new stack which would have to run up the bathroom wall, through a closet on the second floor and eventually through the roof. The vent pipe in the basement has been there for years and I never had a problem with it, so thought it would be a lot easier and better aesthetically to you this.

Here is a rough drawing of how it is set up. I appreciate the input. In the end I want it set up right, so whatever I need to do, I will do.

I am fairly handy, I build, restore race musclecars, hot rods, boats...I am not expert on home building, but remodeled my whole house on my own, with friends overseeing parts of it ie. master electrician friend helped out with electric etc.

Thanks in advance, Tim

The vent comes off the top of the santee for the lav.
A vent lower than that does nothing.

The "cleanout caps" and vent appear to be for a "house trap" and as such are NOT for use as plumbing connections. You have to connect the sewer BEFORE it reaches the trap and connect to a vent that goes out the roof, not one that "vents to another location outside the house".

hj said:

The "cleanout caps" and vent appear to be for a "house trap" and as such are NOT for use as plumbing connections. You have to connect the sewer BEFORE it reaches the trap and connect to a vent that goes out the roof, not one that "vents to another location outside the house".

Click to expand...

there is another location for the drain to connect well before the trap, as the other drain is well before the clean outs/traps

So even though the drains will connect underneath the floor area of the bathroom, I can simply run a vent pipe all the way up through the house, through roof and it will work ok is what you are saying, as long as the vent ends up higher than the toilet/sink etc

I will be running it through the roof and as mentioned my friend will be plumbing it all up, I am just curious about the mechanics of it all.

The old vent in the basement goes out through the foundation, it is right next to the clean outs, does that vent need to remain? why would that vent be there in the first place...as I do have a traditional style vent that goes through the roof...

I appreciate the info, thanks!

Generally speaking, every trap must be vented, and there is a maximum allowed distance between the trap and it's vent, which is determined by the size of the pipe. Your drawing shows no properly vented fixtures.

Local, When you are asking about mechanics of things -- and I am not a plumber, but I have learned so much from reading on here -- one reason that one vents the line for the sink is to prevent the toilet from siphoning the sink's p-trap, which as you know uses a slug of water to prevent sewer gas from running up the pipe and out the sink drain. If one doesn't vent the sink in the manner that Terry describes (and, as Cacher Chick points out, the codes require), water from the toilet rushing down the drain pipe in your drawing will create a suction on the pipe that connects to your sink drain, and, absent a proper vent on that sink line, the suction will suck on the p-trap and pull the water out of it ("siphoning the trap"), leaving it open for sewer gas to come out of. With a proper vent, in other words a vent that connects to the sink line within x-distance from the p-trap and before the connection to the drain for the toilet, the suction sucks from the path of least resistance, the vent, rather than the sink drain. Hope this helps clarify what's going on in sorta layman's terms.

Here is a wonderful guide that Terry often cites to: Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

And here is another guide that I found helpful in better understanding some things in the first guide: http://www.klickitatcounty.org/documentcenter/view/103
Both are done by government officials. (Of course, the codes in your area may be a little different, and different plumbing inspectors in different jurisdictions will emphasize some things over others, but these give you the lay of the land pretty well.)

PS Besides the venting of the sink, and as I think Cacher Chick is saying quite elegantly, you're going to need a vent for the toilet within six linear pipe-feet of the flange, and it doesn't look like that is being addressed either in your drawing.