OATEY P9121A Dearborn® 1-1/2" x 16" Center to Center, Hi-Line/ Slip Joint Combination w/ Baffle Tee

That 16 inches is the distance between the centerlines of the two tailpiece connections on the Dearborn P9121A combination waste, so it sets how far apart your two sink bowls can be. Pipe size is 1-1/2 inch throughout. If your bowl drain centers land further apart than 16 inches, this piece won't reach and you need a longer center to center combination waste.

Either one. The P9121A is built as a Hi-Line/slip joint combination, so the connections take a conventional 1-1/2 inch slip joint tailpiece with a washer and nut, or a Hi-Line connection. That's the point of the piece, one part covers both kinds of sink tailpiece you are likely to find under a double bowl.

The P9121A meets ASTM F 409, the standard for thermoplastic drain fittings and tubular waste, and it is IAPMO listed. Those are the two things an inspector or a spec writer typically wants to see on a plastic tubular waste assembly.

The P9121A is the combination waste arm and baffle tee only. You still need a 1-1/2 inch P-trap and a wall bend or trap adapter to finish the connection to the drain, plus tailpieces for each bowl if you are not reusing the existing ones. Slip joint nuts and washers are the normal consumables to have on the truck for this install.

The baffle inside the tee keeps drain water from one bowl from pushing up into the other bowl on a double sink. Without it, draining a full sink on one side can send water and waste back up the second bowl's tailpiece. On a two-bowl kitchen or utility sink, that is the difference between a clean drain and a callback.

Polypropylene plastic, molded in white. Polypropylene shrugs off drain cleaners and hot water better than chrome-plated brass tube waste, which corrodes and pits over time, so for multi-family and MRO work where the same trap arm gets snaked repeatedly it is a common standard. Where the drain is exposed and finish matters, a chrome tubular waste is the usual choice instead.

No. The P9121A is a 1-1/2 inch fitting, which is the sink and kitchen waste size. A 1-1/4 inch lavatory tailpiece will not seal in it without a reducing slip joint washer, and a double bowl lav is not what this combination waste is built for anyway. For 1-1/4 inch work, use a 1-1/4 inch tubular waste.

P9121A is the manufacturer part number, under the Oatey Dearborn line. It ships as a single piece weighing about half a pound, so it is easy to stock in quantity for a fleet of identical sinks across a property.