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For a brass tub drain and overflow, how would one connect the brass tailpiece to transition to an ABS p-trap?

The issue is that the brass pipes seem to have a different outer diameter compared to ABS pipes of with the same nominal size. My concern is that a trap adapter with a slip joint intended for ABS pipe diameters may not seal properly on the brass tailpiece. There are also trap adapters for copper pipes, but so I have not found an adapter stated for brass.

For illustration, a brass tub drain tailpiece like this:

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Most trap adapters seem intended for ABS on both ends, such as this ABS DWV 1-1/2 Trap Adapter Hub x SJ:

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Though some are intended for copper, like this ABS-Copper Adapter 11/2 HxSJ:

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Would the latter ABS-Copper adapter work on a brass tailpiece? Or is a different adapter needed?

2 Answers 2

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Don't use a slip joint inside the floor. Use a fernco without a trap adapter.

I think but not sure if this was outside the wall, eg a bathroom sink, you would use a rubber slip joint washer instead of nylon to solve this. And if that didn't work .. a fernco.

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  • Shielded Fernco, no?
    – Huesmann
    Jul 9, 2023 at 12:01
  • Yes.............
    – jay613
    Jul 9, 2023 at 12:24
  • The same question applies to a (shielded) no-hub, i.e. fernco, coupling: which one if any has correct diameters for brass? Documentation mentions cast iron, steel, copper, plastic, but not brass.
    – adatum
    Jul 9, 2023 at 15:48
  • Is it against (Canadian) code to have slip joints inside the floor? FYI, the existing original brass drain and overflow pipes slide into the brass Tee and are secured with nylon washers and brass nuts. I planned to use a trap adapter and union joint p-trap to have a removable lower p-trap, since there's no space for a cleanout on or after the p-trap. This is replacing the original trap made of a cast iron drum trap and two elbow fittings, and galvanized steel nipples, one of which was disintegrated and leaking (galvanic corrosion and rust).
    – adatum
    Jul 9, 2023 at 15:48
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    Slip joints can be anywhere, as long as they are "accessible", including in floor structures. It's pretty common to have bathtub SJ drain fittings reachable by means of a removable access panel either in the wall or the ceiling below.
    – kreemoweet
    Jul 21, 2023 at 20:23
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The ABS 1-1/2 Trap Adapter Hub x SJ seems intended for metal pipes on the slip joint side. 1-1/2" ABS pipe does not fit into it. 1-1/2" brass tailpiece fits perfectly.

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    The SJ side is to fit 1 1/2 tubular drain size, of whatever material. Tubular drain can be made of just about anything: various plastics such as ABS, PVC, and most commonly PP (polypropylene), and metal, most commonly brass or plated brass. The ABS side of the fittfings you show are meant for schedule 40 DWV pipe, which again can be made of various metals and plastics. Copper DWV pipe is yet another sizing system, and 1 1/2 in. copper drain pipe has an OD of 1 5/8 in.
    – kreemoweet
    Jul 21, 2023 at 20:27
  • @kreemoweet ABS drain pipes, for example for a tub, have a different OD than schedule 40 DWV pipe? The different actual vs nominal pipe sizes are confusing, and the materials add to the confusion. If you type your response as an answer I will accept it.
    – adatum
    Jul 22, 2023 at 0:08

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