Help identifying P-trap replacement/sizes

Users who are viewing this thread


New Member
Reaction score
Hi all,

I've pulled the tub and replaced all the sub-floor in my bathroom tear-out, now I need to tackle the plumbing. Since I have it all open I feel silly not replacing the tub brass P-trap + drain/overflow. I'd feel a lot better replacing with new if it's not going to be a major PITA. I've attached some images to this post.

From what I can tell it's a regular 1-1/2" brass overflow and waste drain that hooks into a brass P-trap that starts at 1-1/2" slip nut joint (marked "A") to 2"(?) slip nut joint (marked "B"). The nut at location marked "B" is huge, don't have a plumbers wrench large enough to get around it even. From there the other end of the trap joins a threaded steel/iron pipe at location marked "C" and goes onto the rest of the sewer plumbing marked "D". I measure the pipe running "C" to "D" at roughly 2.5" diameter (8" circumference measured w/ a string). I 2.5" OD sounds about right for a 2" ID iron pipe? No way it's 2.5" pipe size in a residential home, I figure.

Any recommendations here? I don't mind to replace everything with PVC but I'm not sure how I feel about those rubber couplings leaving a small joint/crease where the two pipes meet, I hate slow drains and don't want any excuse for hair or junk to build up at a seam.

House was built in the late 60's if that helps identify anything.

1) If I wanted to go PVC - could I get a 2" female iron pipe (FIP) waste connector? Slip nut on the other side to slide into 1-1/2" PVC and do the rest of the plumbing in 1-1/2" PVC? Can't seem to find a waste connector like this anywhere.

2) If I wanted to replace straight up, I believe it's this?

3) Alternatively, should I just pull the 1-1/2" drain plumbing and take a look in the trap? If it's not corroded or rough, just leave it?? Are the slip nut washers common sizes where I could buy a new one to replace it at the joint of "A"?

Advice is gladly welcomed, thank you.


  • 1_resized_m.jpg
    55.2 KB · Views: 136
  • 2_resized_m.jpg
    69.6 KB · Views: 132
  • 3_resized_m.jpg
    51 KB · Views: 129
  • 4_resized.jpg
    51.7 KB · Views: 137


Licensed plumbing contractor
Reaction score
San Francisco Bay Area
You should scrap out all the galvanized drainage piping and fittings.
The old durham cast iron fittings and piping are so old that now is the time to do the replacement.
This looks like second floor. We always use cast iron where noise can be an issue. Though, in the horizontal plane, not much noise from plastic.
Yes, common slip joint washers are still available in square cut, but modern waste and overflow use beveled washers.
Slip joint connections must remain accessible permanently for future access or use glue joint waste/overflow if you don't want to rely on access panel.
In confined space like you have, I recommend you hire a licensed professional.
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks