Hello,

My home (built 1965) was "roughed in" for a toilet in the basement. It was built with a laundry tub, and the washing machine discharge goes into the laundry tub which drains to a 1.5" drain pipe to the floor.

I previously added the toilet (no problem), but I'd also like to add a small sink next to the toilet. The sink will be 3' away from the drain pipe for the utility tub. Can I plumb the sink drain to the same pipe as the laundry tub?

If not, there is a another pipe coming out of the floor near there which connects to this laundry tub pipe via the vent pipe going up. I think this vent is for the toilet. Can I tap into this pipe and for my sink drain? This pipe is 1 foot away from where I want to put my sink.

Or do I have to bust up concrete? Check out these photos. Thanks.







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Yes, you need a tee in that vertical section of copper behind the sink. That other PVC is a partial S-trap and can not, by code , be used for the lavatory. It could have been if it had not been rolled up. It needs to be capped off now, with a rubber test cap.

you can use that plastic pipe for the vanity but it will not be legal unless it is vented.
i would remove the plastic, screw a plug into the brass opening and cut a 2 x 1 1/2 inch sanitary tee into the vertical pipe behind the vanity. put the center of the san tee at about 19-20 inches.
you can get sheilded stainless couplings to adapy from copper to PVC. also put a cleanout tee into the 2 inch ..

To both responders:

Much thanks. I was the one that started to add the white PVC to the laundry tub pipe. So I will just cap this off and use it as it was intended - - for a clean-out. Correct?

You say it's fine for me to tap into that vertical section right behind where I intend to put the new small sink? I had not thought of that before since I THOUGHT that was for the toilet vent system and was not available for tapping into for a drain. But you say this pipe IS AVAILABLE for me to use for my sink drain?

If you can re-confirm this, then I'm "good to go." Thanks a lot.

Yes, cap or plug the PVC pipe.
Yes, use the toilet vent for a lavatory drain.

The toilet would now be wet vented instead of dry vented.

Steve - - I'm not sure what your note means, even though I understand what "wet vented" means. Do you think this would be an issue for a local inspector looking for a "code violation?" The vent pipe (as well as all of the piping in these photos) is 1.5" copper pipe. I seem to have read somewhere that if I turn a W.C. vent from a dry vent to a wet vent, I need to have the vent pipe the "next size larger." Does that mean a 1.5" dry vent can't be converted to a wet vent? Or would the code in 1965 allow me to add the sink with a 1.5" vent? Any guidance you (or others) can provide would be much appreciated.



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given that it is an existing situation, the inspector would have to be very hard a$$ to not allow your putting a san tee into the vertical copper behind the vanity..
after all, the tailpiece on the vanity is 1 1/4 inch..

MN Plbg Code 4715.2550 WET VENTING (A) "not more than one fixture unit is drained into a 1½ inch diameter wet vent or not more than four fixture units drain into a two inch wet vent;"

Also from that section - "Subp. 4. Water closet. A lavatory may be connected to a properly installed vent from a floor-set water closet."

The vanity is a 1 fixture unit fixture.



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Steve,

Regarding your last note, I'm sorry to say I'm still confused. Do the codes you referenced mean that it is okay for me to tap into this 1.5" vent and install a 1.25" sink drain? Or can't I do it because it's a vent for the toilet. Your last summary sentence left me still wondering if I'm okay - - - or not.

Thanks a lot.

Dan

You should be good to drain the lavatory into the "properly installed floor-set toilet vent". The sink is 1 fixture unit and the first part of the code section states it's ok to drain a 1 fixture unit into an 1½" wet vent.

getting technical about this...
the minimum size pipe allowed underground is 2 inch. so the 1 1/2 inch copper vent is illegal to start out with.
so, if your inspector wanted to be a hard a$$ about this, you could be made to bust up the floor and change the 1 1/2 to 2...
relax.. install a san tee into the vent and it will be fine...

Much thanks for everyone's help. This is a terrific forum for people (like me) to get knowledgeable feedback and guidance on all kinds of plumbing issues. I didn't expect to get so much great (and quick) input, and I want you to know I really appreciate it.



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Packy, if you look at the laundry drain, it's CI in the ground(probably 2" and reduced to 1½" copper at floor level. The toilet vent might be the same.

No, there's a good picture of it, the 1 1/2" copper comes up out of the slab, they have sweated a coupling a few inches above the slab to continue on with the vent.

Thanks, NC. I looked at first and third pics and somehow didn't see the #2 pic showing the copper coming out from the slab.

Thanks again for all the help. Can I ask one more question?

I'll be using this 1.5" toilet vent for my small 1.25" sink drain. I'm also replacing the toilet with a new one. Is it possible that flushing the toilet will suck the water from the sink P-trap because the toilet vent is 1.5" instead of 2" per current code? My house is a 1100 square foot rambler (nothing fancy), so there are no long runs of venting. But I'd hate to get this all installed and find that my sink trap is sucked dry when I flush the toilet. Do you think this could be an issue with the 1.5" vent? Or should I "not worry at all"? Thanks.

Packy - - Do you think there is any way I'd have an issue with too much "sucking" from the 1.5" vent when the toilet flushes? Could it suck out the sink trap water? Or do you think there's "no way" this could be an issue? My house is modest size, single floor (with basement where the sink is going). Your opinion (and assurance) would be appreciated. Regards,

Dan the illegal part of the vent is, any piping in the ground needs to be a minimum of 2". Your code allows an 1½" vent for a toilet(mine doesn't), so the above ground 1½" is ok by code. I wouldn't worry about the trap getting siphoned.

Steve,

Could I please follow up with you one more time? I'm probably going to install the sink in the 1.5" toilet vent regardless, but it would be good if all agreed (including my city inspector) that it met Minnesota code. I called the city inspector, and I cited the following comment from you (which I believe you got from a document called "2012 Minnesota Plumbing Code Chapter 4715) at this web site:

[www.dli.mn.gov]

"Subp. 4. Water closet. A lavatory may be connected to a properly installed vent from a floor-set water closet."

She then quoted me from a Minnesota Plumbing Code document dated 1983 - - on page 63 of this document:

[www.revisor.mn.gov]

It has the same words, but with the following words added: " . . . , provided the vent is not less than two inches in diameter."

I tried to explain to her that when the house was built (1965), the 1.5" toilet vent was "properly installed," but she keyed in on the "two inches" statement in the 1983 document. Do you think the 2012 document "trumps" the 1983 document, or maybe there's another part of the 2012 document which defines a "properly installed vent from a floor-set water closet."

I think the 2012 document should give me the "go" to use it and meet Minnesota code. Do you agree?

Sorry this is so complex. I appreciate your help with this - - very much so.

Dan, what I feel means nothing on this matter, if the inspector says no.

According to the 1983 MN Code and the 2012 MN Code, 2" is the minimum vent for a toilet, in-ground or above doesn't matter. A toilet is rated as a 6 fixture unit fixture and the vent sizing chart specifically states that a 6 DFU fixture can't use an 1½" vent. I don't know what the code was when the house was built, regarding vent sizing. Maybe 1½" was allowed then, OR could the toilet have been installed after the house was built and done without a permit? Now did the inspector state only the wet vented section of the toilet vent needed to be 2" or the entire length? Written Code states the whole vent.

Now why the Section 4715.2550 Subp 4 number was used in both the 1983 and 2012 codes, but rewritten, relaxing the written requirement for 2" vent is anyone's guess. If in 1965 an 1½" vent was allowed for a toilet, being that you are modifying an existing installation, you have to abide by current code, unless AHJ allows for a variant.