1 1/2" vent tied in to 2" waste?

[edee_em]

Redoing main floor powder room (toilet and vanity out, flooring soon) and noticed the vent for the sink is 1 1/2" ABS tied in to the drain which is 2"
ABS. This sink drain runs the length of the powder room (under the floor obviously) back to a stack.

Was there any reason for them to go with the larger size drain pipe? Is that code (I'm in Ontario, Canada) If not, I don't mind leaving it except that where the vent to drain connection is taking up space I could use to move the cold water supply over a bit to the left as the new vanity has a precut opening in the back and the supplies don't currently line up with that opening.

What I was thinking of is cutting out the connection point, running 1 1/2" ABS down through the floor and tie in to the 2" in the basement. The connection at the stack is hidden by a basement remodel.

 

[frodo]

a lav drain can be 1.5'' as long as it is one sink draining into that line and nothing else

it is the bare minimum requirement, it is also something that plumbers will not do, yes it is legal

but it will clog up in a heart beat and be nothing but trouble.

you have the info to make your own choice



no you can not reduce from 2'' to 1.5

 

[Mr_David]

1-1\2" vent is okay. Like Frodo said. If it's already 2" to the sanitary tee, best to keep it that way. You can use 1-1/4" trap and trap arm, BUT best to keep that at 1-1/2" a well.

 

[edee_em]

Thanks guys

It is a powder room so I don't imagine much more than hand-washing goes on in that sink. I'm hearing you both about keeping the 2" line after the trap and I can see the reasoning for that. Thinking about it, we have never had a clog in that sink in over 30 years.

Just to make clear what I have. I think I forgot to mention the trap and tee earlier: 1 1/2" vent pipe connected to 1 1/2 x 2" tee (which has 1 1/2" trap connected to it) connected to 2" drain that is connected to the stack.

I don't want to replace the 1 1/2" vent nor the 2" drain. My question is would it be okay to take out the 1 1/2 x 2 tee and replace it with a 1 1/2" x 1 1/2" tee, then replace that bit of the 2" pipe below the trap to the floor (about a foot or so) with 1 1/2" through the floor and then couple that 1 1/2" back to the 2" that is there.

The only issue with this, if I am correct (and probably not, that's why I'm asking you pros) is that by reducing the tee and pipe after the trap could cause some issues even though it is still draining in to the 2" drain.

 

[frodo]

as I explained before

you can do it, I would not, we call that....jerry-rigged or something else, but we call it rigged

but it is your house to do as you wish

 

[edee_em]

I was able to get into the plumbing a bit more and saw that the 2" drain from the vanity is connected to the toilet drain by a 2"x3" or 3"x2" connection (not sure about the proper terminology). The toilet connection continues straight down into a wye and then into the main stack going out to the sewer. It looks like the sink and it's vent is venting the toilet and I imagine that is the reason for the 2" drain. Is that correct?

So thank you Mr. Frodo for being consistent with your warning that I not "rig" the setup!

 

[SHEPLMBR]

Some places do not allow 1-1/2 below concrete