waste pump under kitchen sink

[Thomas Jansson]

Never seen this before... waste pump mounted under kitchen sink. This is on the eleventh floor of an industrial loft conversion in downtown Chicago.

Why would they do this? Pump body has an air admittance valve... was it to save on running a vent to the roof? Unit was owned by a major commercial contractor (not present at inspection so I couldn't ask). Aside from the "big boys with big toys" phenom, What reasons could there be for this?

[Ian Gills]

That is a beautiful chrome drain. And the pump is a Zoeller. Wow. Obviously not a cheap fix. Looking at where the drain exits after the pump, is this low enough from the sink if the pump were to be removed? It looks like the pump may be there to allow the drain pipe to drop far enough before the U-bend (isn't 18 inches required?).

[sparksnmore]

Looks like the sink could gravity drain if the tee was removed and the tail piece shortened.
I wonder what the tee above the trap is for?

[Thomas Jansson]

Tee above the trap is for the second basin. It's a two-basin kitchen sink.

Ian, I like your idea about there not being enough of a drop... the wall tube does enter the stack a little on the high side. Any plumbers have code or best practices for this?

Also, I realized that maybe the air admittance valve has more to do with the operation of the pump itself than it has to do with venting issues in the stack. If anyone has some insight I'd appreciate it.

Thanks for your feedback. That's why NACHI ROCKS.
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