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I'm remodeling my bathroom. The sink drainage come up from the floor. The alignment between that and the drain coming from the sink doesn't have enough space for a p-trap to be installed so it just falls into place and connects the two (prior to remodel there was no p-trap).

I was thinking having a 45 degree pipe come out of the sink, forward then down, then attach the p-trap, and that would allow enough space for overflow to go back and down to floor drain pipe. My crude image of what I mean, circled in red.PTrapImage

Would this allow for proper drainage?

auujay
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Noob
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  • Have you had any sewer gas smells up to this point? This is perhaps unlikely, but what is the possibility that there is already a P-trap in the floor? If there is, you don't need to add another trap above it. – Grunthos Jun 10 '14 at 14:08

4 Answers4

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When you purchase a P-trap from the hardware store, you'll end up with these pieces (or something similar).

P-Trap pieces

You'll also want to pick up a 1-1/2 in. PVC 90° slip-joint elbow while you're there.

1-1/2 in. PVC 90° slip-joint elbow

You'll then want to connect the pieces something like this...

Connect these pieces

You'll then have to twist the pieces around, until you can get them to fit together. You'll end up with something similar to this.

twisted p-traptwisted p-trap

Though I'm not sure this is code compliant anymore.

In the 2003 version of International Residential Code (IRC), there was this section.

International Residential Code 2003

Chapter 31 Vents

Section P3105 Fixture Vents

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 P3201.7.
  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.

FIGURE P3105.3 VERTICAL LEG FIXTURE DRAIN SCHEMATIC

However, in the 2006 version, this section is gone.

Community
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Tester101
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    Not allowed by code for new construction, the water seal can be siphoned out by too high a water flow in an s-trap arrangement. For old construction, be aware of the water siphon effect and if you empty a sink full of water, run a pint of water through after the bowl empties. And since it didn't have a trap before, it's better than no trap at all. – Fiasco Labs Jun 10 '14 at 15:50
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You're going to have to use an AAV... S-traps have long ago been illegal for the siphon issue that you mentioned.

enter image description here

FreeMan
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Russell Hayes
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  • Does this mean that with an AAV this is no longer considered an S-trap? I assumed just the straight leg (the horizontal pipe in the image) was sufficient. – Michael Mior Mar 19 '24 at 12:51
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My 2 cents:

Mine didn't line up. I did the following, but check for your local code....

How I did it

Marinaio
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When the drain goes vertically like this, it is often called an S-trap, since it is shaped like a letter S instead of a letter P.

drain S-trap

That center connection in the S-trap is a swivel. You can do it without the 45-degree section if you rotate the center connection. You can see that in this example:

angled S-trap

The more you rotate the center joint, the closer together the input and output are.

Will this be visible to the room, or enclosed in a cabinet? If it is visible, I can imagine perhaps wanting the aesthetics of a straight symmetrical drain. If it's hidden inside, just use the S-trap without the 45-degree lead-in.

Grunthos
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  • Thanks for your reply! However, from what I have read, it seems that s traps are heavily deprecated due to siphoning. Is this not the case in this configuration? – Noob Jun 10 '14 at 13:48
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    S-traps are not code compliant in most location. – Tester101 Jun 10 '14 at 13:52
  • That's a different question. If you don't have a drain in the wall with a vent stack, it's not a P-trap. If the drain pipe is in the floor, you have an S-trap. In either of the proposed configurations, either your original with the 45 or my suggestion without, both are absolutely S-trap configurations. Even if the S-trap does siphon, it can't be worse than the previous no-trap drain. You can try putting the trap as low as possible, so that the sink-to-trap section is the longest, and the trap-to-floor section is shortest, to reduce the siphon-prone drop part. – Grunthos Jun 10 '14 at 14:02