Venting utility sink, WC, and washing machine

[Andrew Schrader]

Happy Tuesday everyone,

Thanks in advance for your time reading and/ or commenting.

My current laundry room has just a washer/ dryer in it and I'm adding a water closet & utility sink. I'm in Montana with UPC code. I have the walls open so access to do anything really.

Today my washing machine standpoint has the P trap below the floor, unvented and it works fine.

I'm adding a utility sink in it's physical location with a toilet next to it. The washer will be in the other corner of the room.

1. My understanding is that I cannot wet vent the utility sink with the water closet. 2" drain to the utility sink San tee, 1.5" up. That would be very convenient. Do I need to run a second dry vent from the 3" WC drain? Can I connect that toilet dry vent with the utility sink vent (above 42").

2. Is there any benefit or code requirement from connecting the utility sink 2" drain into the 3" WC drain vs connecting it to the existing drain from my kitchen sink ~8' away? Kitchen sink 2" drain is probably an easier connection.

Thanks! Andrew

 

[Reach4]

Can I connect that toilet dry vent with the utility sink vent (above 42").

Yes.

Is there any benefit or code requirement from connecting the utility sink 2" drain into the 3" WC drain vs connecting it to the existing drain from my kitchen sink ~8' away? Kitchen sink 2" drain is probably an easier connection.

Not sure. If the toilet were wet-vented by the lav, you would need the standpipe to connect downstream of those. Joining with kitchen 2-inch? I suspect it is OK, and it might help wash kitchen waste along. But I guess you could say that about the toilet too.

Kitchen drains tend to clog where they turn from vertical to horizontal. So if doing changes, you might take the opportunity to add a cleanout. Plus, if the kitchen waste goes vertical to horizontal, that should be via a long sweep. If you don't have that, that would be a good upgrade-- even if there were no code.

 

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[Andrew Schrader]

Thanks @Reach4 Today that kitchen 2" drain comes vertically up ~8" then drops back down into the top of a 2" combo. I'm going to cut out the 2" combo and install a long radius 90 elbow (with cleanout) so the drain doesn't have to come up 8". Not sure how it hasn't plugged or backed up. I assume that pipe will be full of water and whatever else when I cut it apart.


Do you know the reasoning why the code doesn't allow wet venting a WC through a utility sink 2" drain?

 

[Reach4]

Do you know the reasoning why the code doesn't allow wet venting a WC through a utility sink 2" drain?

For horizontal wet venting, they limit that to bathroom groups. Thought is that you are not going to be using multiple bathroom fixtures all at the same time. Maybe for vertical wet venting too. There is also stack venting... not sure about that one.

Take a look at IPC venting https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf , and see what you think.

 

[Andrew Schrader]

I'll be using a deep utility sink as the lav in my bathroom/ utility room. I assume wet venting through the utility sink vent would work fine, but may not be code compliant.

 

[Reach4]

I'll be using a deep utility sink as the lav in my bathroom/ utility room. I assume wet venting through the utility sink vent would work fine, but may not be code compliant.

Maybe think of it as a big squarish lavatory or a small elevated bathtub.