New laundry tub & DWV pipes connections

In My Humble Opinion
1

From the “how the hell…” files:

We got a new laundry tub this past weekend to replace the scummy one that came with the house. Problem is, I can’t figure fo rthe life of me how to install it. I figured it would be simple, and it will be as soon as I can attach these stupid threaded “nuts” that came with it! two connections are supposed to use these things (from sink drain to pipe, and pipe to main drain), the rest are glue.

Here’s what I have:

The bottom of the sink’s drain is a short, inch or so of a pipe with threads on the outside. This piece isn’t detachable, it’s molded right from the plastic the sink is made from.

It came with a white plastic “nut” that has a plastic o-ring or washer inside. It is open at both ends, with threads on the inside of one end. The other end has a bit of a ridge to it, making the opening slightly smaller on that side.

I bought a kit of all the elbows, sanitary taps, etc I should need. I also bought a length of DWV pipe to run to the main drain, and the glue and brush.
Now, I have everything figured out, except how the threaded attachment is supposed to work. The DWV pipe itself doesn’t fit through the “nut” because of the little ridge on the inside, and even if it did fit in that opening, there’s nothing to ‘grab it’.

The threaded side of the “nut” (I assume screws directly to the threaded bits on the sink and the main drain), but how does the DWV pipe attach to the other side of the nut? I unscrewed the exisitng one, but don’t remember any trick to it. I unscrewed it, and it came apart; the old pipe, the nut and the main drain all separated pretty easily if I remember right.

The new kit came with one insert piece that, because I can find no other use for it, I assume has to do with this threaded connection. It’s a slightly smaller (in diameter) plastic piece that has an outward ridge on one end. When I place it through the open end of the “nut” (it fits!) the ridge catches on the nut’s inward ridge and it hangs down, somewhat in place (a little loose because of the slightly smaller diameter. OK, so now I have the nut with the plastic insert hanging down. Do I fit that insert into the DWV pipe now? If so, how does it ‘catch’ on?

Help, Mrs. RumMunkey needs to do laundry and right now there’s an assortment of pipes, elbows and tools instead of a working laundry tub!

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Sorry to reply to my own post, but I found a picture if my description make s no sense.

Here is a kit at Home Depot. The “nut” I tried to describe seems to be affixed at the top and bottom of the vertical pipe in the picture.

In fact, this particular kit seems to use all threaded connections instead of just two like mine.

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Heh. Home plumbing is an arcana, isn’t it?

As I recall from my last sink installation, the pipe with the ridge, as you suspect, connects to the drain. Then, you connect the trap to that using, essentially, big washers with holes that fit snugly to the vertical pipe and that screw onto the pipes of the trap… Friction (and the geometry of the pipes) holds the whole thing in place.

You should just be able to get a trap kit at the local hardware store that will have most of the hardware for connecting it. You might have to get an adapter that connects the output of the trap (screwed) to the rest of the plumbing (glued).