Washing Machine Standpipe Venting

Old 06-23-16, 10:00 AM
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Question Washing Machine Standpipe Venting

I am a brand new home owner and first time poster! This is my first major project and I'm naturally struggling to comprehend all of the code (Michigan, US). So, I apologize in advance for my ignorance in plumbing . I really appreciate the help.

In my new house, there are not currently provisions to drain the washing machine. I would like to locate it in the basement, right near the main drain pipe coming from the upstairs. If acceptable, I'd like to splice into this drain pipe and add a standpipe for the washer. There is also a sink drain from the basement bathroom that is spliced into the main drain at the same location that I'm considering. I've found the appropriate dimensions for the standpipe/trap. From my understanding, the drain needs to be 2" pipe with the P-trap 6-18" inches above floor, a standpipe height of 18" to 30", and with the washer indirect connection located above the washer fill line. However, I'm very unsure about venting. I've seen in the code that every trap must be sufficiently vented but I'm struggling to comprehend what constitutes as a appropriate (wet?) vent.

I have drawn a quick diagram of my situation. Can anyone be so kind as to help teach me what an appropriate vent for this setup would be?

Thank you SO much.

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Old 06-23-16, 01:29 PM
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Assuming that there are other fixtures on the upper floor(s) draining into that main vertical there really needs to be a "re-vent" from all the fixtures in the basement. Vents need to be no more than a specified distance from the trap outlet, depending upon the diameter of the trap. The re-vent piping will be arranged to vent all the traps and will tie in to the main stack above any drains into the stack.

Study these Google images and post back if you need clarification.

Old 06-24-16, 09:45 AM
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Thanks for the answer Furd! I appreciate it.

I'll have to take a good look to see how feasible venting is without tearing into the whole house.

Are there other alternatives such as an AAV? I live in Michigan, so I think they are permitted. While I completely understand that an atmospheric vent is better, I'm just trying to understand all of my options .

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Thanks guys!
Old 06-25-16, 07:48 PM
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The AAV is usually a good solution for a basement if it's allowed in your locale. The AAV though in your drawing should be as high as possible, certainly above the standpipe for the washer. You should use a combo-wye for the horizontal to vertical AAV connection.

You'll likely also need a second AAV similarly connected to the sink, since the sink needs it's own vent too.

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