Need ID: Is This a Trap Adapter Flare (Floor Drain ‘Mushroom’)?

[Redrabbitdownthehole]

Hi everyone,

I’m working on removing an old metal S‑trap that drops straight into a floor drain. The floor drain has what looks like a flared trap adapter (the “mushroom”‑shaped flare), and I’m trying to remove the vertical trap arm that inserts into it.

Here’s what happened:

• The J‑bend broke apart when I tried to remove it — the metal was extremely brittle.
• The slip‑joint nut at the top (J‑bend → trap arm) turned, but the J‑bend would not pull out.
• The vertical trap arm going into the floor drain also will not pull out.
• After cleaning the area above the flare with a wire brush, I cannot see or feel any nut or ferrule. The metal looks like one smooth piece of pipe.
• The underside of the floor drain clearly shows the flared fitting, but I want to confirm exactly what it is.

My questions for the pros:

1. From my photos, can you confirm whether this is a standard floor‑drain Trap Adapter Flare (flared trap adapter)?
2. Is it normal for the ferrule and nut to completely fuse into the trap arm so that the pipe looks like one smooth piece?
3. If the nut had broken off, would the ferrule alone still hold the trap arm tightly enough that it won’t pull out?
4. Is cutting the trap arm ¼–½ inch above the flare the correct removal method in this situation?
5. Is there any chance this is NOT a trap adapter flare, and if so, what else could it be?

I’ve attached photos of the top and underside of the flare after cleaning.

Any confirmation or advice from those who have dealt with these old floor‑drain S‑traps would be greatly appreciated.

Thanks!

 

[Reach4]

I am not a pro.
The rusty thing at the floor is an escutcheon. The stuff in picture 3 and 4 are going to get cut out. The drain basket in the sink might have to be replaced. Out of the drain basket is the tailpiece. The tailpiece goes to the input of the P-trap.

You want an AAV above a sanitary tee (santee). You want a slip-joint plastic P- trap to feed into the santee.

If you don't have reasonable access from below, you will measure the OD of your pipe going into the floor. You will probably measure 1.5 inches. (if you have access from below, you would probably bring new 1.5 inch PVC (1.90 OD) up through the floor.

You would cut the pipe to maybe 2 or 3 inches above the floor of the cabinet. You use a trap adapter to convert to PVC.

That PVC could have a jog with 45s. Vertical space is needed to have a good jog. The jog might be needed to allow the new trap arm to be at least 1.5*2=3 inches long (measured from the output of the U of the trap) to the sante body. Expect the trap to be doubled back on itself. It is possible that you could use a "double offset" to introduce a jog, if you have enough vertical space.

The sanitary tee would have a trap adapter in the side port.

Here are some threads to look thru:

How to add AAV

My wife and I just bought a home (built 1901) and are having an issue with our double kitchen sink barely draining and backing up if the faucet is on for about a minute or more. We checked to make sure there wasn't a clog. The run from the kitchen to the vent stack/main drain is 25+ feet, and...

terrylove.com

2 Air Admittance Valves on double sink, IPC 2009

Hey All, My local inspector allowed me to use AAVs on my kitchen double sink, as there was no good way to hard vent it. He said that a double wye with an AAV off the top was not allowed in our municipality, and that I have to have 2 AAVs. I guess a 2" hard vent is ok off the top of a double...

terrylove.com

There are more threads that describe using an AAV into the floor with an offset.