Trapped Again

The half bath had an interesting trap that I have not seen. Do you know what type it is?

At the laundry the drain was fixed and it appeared to have a PVC back flow.

Is that a trap? If not does it need one? Do stand pipes to fixed drains need traps?


By the way a group named South side Johnny sang a song trapped again.

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Pic 1 looks like it may be a Bottle Trap

If that’s a 2" into the slab it could have been roughed-in for a shower with the trap below the slab and later converted for a laundry sink.

I haven’t seen PVC back-flo devices so that’s a new one on me.

It may not of been a back flow but when I was trying to read it just had arrows indicating the flow direction. The writing was on the side towards the foundation.

Found it :smiley:


Should there be a trap installed?

Yes You need a trap under that utility tub…

Maybe the owner (or someone) thinks that a spring loaded check will keep gas from coming back through to the laundry tub? Needs a trap. Laundry tubs drain all type of debris (lint, etc.) that will get behind the seal in a check and prohibit it from closing.

Thanks guys.

This is the 1st time I have seen this type of backflow?

I did report that there shuold be a trap installed.

Mike , I have never seen a bottle trap, but my first thought was a drum trap which is not considered sufficient.
Is a bottle trap enough of a water barrier ?

Bob, the answer is depends but probably no. Up to the AHJ as always.

From one of the manufacturers:

Please note that bottle traps (all brands) may not be per code (meaning they may not be legal) in your area.
It would be best to check with your local plumbing code before purchasing and installing them.
Bottle traps are used in many countries as the “standard” trap but not in the U.S.

Must be a version of a drum trap then.
I get these on many inspections , under tubs and upside down so the tub water hits you in the face when you rod from the basement…


It seems clear it is a bottle trap.

Drum trap have cleanout access on the bottom side.

Same kind of design is<nt Mike?
Other than the clean out it seems to function the dame.
By the way I have seen 100’s of drum traps not upside down in apartments , where they are usually placed between the tub and toilet.
It is flush mounted to the flloor with a chrome cap.

Not really. A bottle trap has an internal partion. Here is a design view of a bottle trap.


ah , very interesting.The design is like a regular drain trap internaly.
What is the problem with them?

The potential of a leak at the partition due to corrosion or defect.

They are commom in other parts of teh world but not here.

Then it would lose the water barrier.