Plumbing a utility sink with no vent into floor standpipe

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So I currently have a washing machine that has its hose running into a 2" standpipe that is coming out of my basement floor. A humidifier hose and AC hose also squeezes into that standpipe and it's pretty tight and janky looking. I'm trying to clean everything up with proper piping, install a laundry box and also a utility sink.

There is no vent or additional plumbing nearby that is easily accessible.

The standpipe is on the left, machine in the middle and the sink would be on the right. Can I have a single PVC pipe that connects the sink to the machine that then connects to the standpipe? Do I need a mechanical vent for it to work? It all seemed to work fine before but I am sure it wasn't to code (Toronto). What is the best way to connect the humidifier and AC to the same pipe? Should I have individual connections piped to the standpipe?

The images below in order:
1. Standpipe on the left with humidifier and laundry machine draining into it

2. Current situation diagram

3. Photo of the new wall I framed to hide the plumbing behind

4. Proposed diagram of plumbing the sink and laundry to the standpipe

5. Another proposed option


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Last edited:
Hey, wait a minute.

This is awkward, but...

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