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Discussion Starter · #1 ·
I removed a half wall when I remodeled my kitchen. The sink drain pipe was inside this wall. The drain went through the floor, but it also had a high loop in it, looping back on itself (about a 3-foot high loop). I assume this loop relieves air pressure in the pipe . I am now in the process of rerunning the drain from the new sink location. My question is, can I simply run the drain through the floor to the existing drain pipe, or do I need to create a loop? Thanks...

Tim
 

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Sounds like an island vent- see picture
You need to keep it, either in the wall or inside the cabinet.
In my area I can now use a mech vent(AAV), but only at island sink locations. You might consider the same, but do not just hook the trap to the drain line. That create an "s" trap which is prone to self siphoning, therefore, not allowed any more
 

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Thanks...that's it except there is no connection to an air vent and the pipe loops back on itself, connecting to a single 90 degree elbow on the drain pipe in the floor. I don't see any air vent at all. There was an air gap in the sink for the dishwasher, but we don't have one with in the new sink. Does it make sense to have no true vent and just a loop?
 

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Thanks...that's it except there is no connection to an air vent and the pipe loops back on itself, connecting to a single 90 degree elbow on the drain pipe in the floor. I don't see any air vent at all. There was an air gap in the sink for the dishwasher, but we don't have one with in the new sink. Does it make sense to have no true vent and just a loop?
I've seen situations like this before where people have seen plumbers put in a loop vent, and try to duplicate it, but i think it's just too hard for some people to figure out.

The loop you're describing makes no sense. There isn't another pathway for the air to follow, so it's a useless waste of fittings.

The one shown in the picture above is the way to do a true loop vent. Check your local code, you may be able to use an air admittance valve, as suggested above.
 
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