Would you call this an S trap?

What say you?

YES if less than two times diameter of the pipe (3 inches here)
Go from end of first to start of bend in other .
Looks to need about an inch of horizontal to me from the picture.


I did not realize there was a formula for that. Thanks. And you are accurate, the horizontal section is only about an inch.

No. I would call this a Strap.



It’s an attempt at a “vertical leg waste drain.” The minimum dimension of the horizontal piece after the trap is 8 inches.

When installed properly, they were allowed through the 2003 code cycles. They have since been removed from the model codes, although some localities may still allow them.

s traps.jpg

vertical leg fixture drain.jpg

Not much of an attempt Jeff

P3105.3 Vertical leg for waste fixture drains. A vertical leg
(see Figure P3105.3) is permitted within a fixture drain of a
waste fixture in accordance with the following criteria:

  1. Minimum trap diameter shall be in accordance with Table
  2. The diameter of Section A shall be equal to the diameter
    of the trap.
  3. The length of Section A shall not be less than 8 inches
    (203 mm) and in accordance with Table P3105.1.
  4. The diameter of Section B shall be one pipe size larger
    than the diameter of Section A.
  5. The length of Section B shall not be more than 36 inches
    (914 mm).
  6. The diameter of Section C shall be one pipe size larger
    than the diameter of Section B.
  7. The total length of Section A and Section C shall not exceed
    the distance allowed in Table P3105.1.
  8. Bends shall be the diameter of the largest connected section.
    P3105.4 Crown vent. A vent shall not be installed within two
    pipe diameters of the trap weir.
    SECTION P3106

s traps.jpg

I didn’t say it was successful :smiley:

Would you report is as an defect? Given the location it appears to be a sink in a bathroom, I would not as I see no major issues or adverse effects it would cause.

New construction yes. Older homes no.

This installation was in a newly gut renovated apartment. I’m going to call it out. The project manager of the renovation work is an architect. How about them apples.

New or old, it’s an improper trap configuration. Yes, I would call it out.

Why do you think the laws of physics prevent the trap from emptying and allowing sewer gas to enter in a older home?


Not what I said. I understand what you’re saying but do you personally report a s trap a defect? General summary defect? I’m not going into great detail or debate here but for me its a case by case basis.

Newer home, remodeled yes. Older home just a general comment about potential issues.

This pic in this thread does not appear to be a true s trap anyways. Is it vented? It looks like it’s vented. It goes through the wall, not floor. Being remodeled, would say defect. Calling it a s trap no.

Ray, if it’s not a “true S trap”, and you’re not calling it out for that, what would you call out as the defect then in a remodeled home?

Ray last summer my village guy for turning on water at a vacant showed up at a home I was inspecting and immediately called out the S trap similar to what is in this picture.
I sure would have felt foolish leaving it out.
House was 75 years old.

Since it doesn’t go through the floor, no.

In much older homes, I call them out as being allowed at the time of construction, but no longer likely permitted and state the reasons.

In newer homes, I call them out as a defect.

Funny how they are still, basically, installing s-trap (or should I say impurely vented) fixtures in mobile homes. Boca Vents are installed at virtually every fixture.

IN old homes, plumbers shange the configuration of the s-traps slightly, and install AAVs to help eliminate some of the problems.

Stay away from quoting codes, kiddies…

Observe and report the concern, and reason for it, without getting into what is “allowed”. Stick with the mechanics of why s-traps are problematic and move on from there.

Guess that’s why you are an Electrician and not a Plumber.

Funny Bob :slight_smile: But you must have me confused with someone else Sir, I was a Master Plumber and also a Master Mechanic and Warm Air Heating Supervisor for over 40 years. (retired 9 years ago)

Odly enough, up until the time I retired, my city didn’t require an electrician’s ticket, all you had to do was say “I am one” and you were. The jobs still required the same permits and inspections though and electricians must pass the block test now.

I said that I wouldn’t call it an “S” trap because it doesn’t go through the floor, a technicality. Lower the tail piece down 6" or so and what is it then?

Joe, I am with you 100% with not calling out codes. Code or not, if there is an issue with it, it’s an issue and state why you feel it is an issue. Plus, you wouldn’t want to get embarrassed by licensed plumber, that the seller calls in, who should be able to quote the code front and back - and better than most of us can. We are NOT code officials or code enforcers.