I have a new bathroom which plumbs the shower into the main stack via a 2” PVC pipe. My understanding is that the distance from the trap weir to a (in this case wet) vent can be up to 8”.

My shower weir-to-vent distance is about 7'9", properly graded at 1/4” per foot, so it would appear I am in the clear as far as siphoning and any vent issues go. However, I am hearing different takes on whether my long drain constitutes a trap arm which should not be more than 5’ in length.

enter image description here

Just in case, I installed a separate extra vent (pointed to in red) to the right of the p-trap, that goes through the wall in the shower and into the attic, where it terminates in a AAV (Studor valve), which in itself is legal per my local regulations (and IPC 2015).

extra vent1

extra vent2

extra vent3

My questions:

  1. Is my sub-8-foot weir-to-vent plumbing to code as far as IPC 2015?
  2. If it is not, will my extra vent be an IPC 2015-permissible way to vent the shower?
  3. I don’t like the idea of having metal straps rubbing against the PVC piping, so I am inserting rubber between them (see example photo). Is there anything wrong with that? rubber gasket
  • Anyone? Bueller?
    – sil80
    Jun 22, 2021 at 13:43

1 Answer 1


Your vent configuration is fine, if unusual.

Not sure about the rubber bushing. Seems like you are inventing a solution to metal straps severing PVC pipes. I've never noticed an epidemic of metal straps severing PVC. If you don't want to use the strap, replace it with a J-hook. They are sold at any plumbing supplier.

  • Jeff, much appreciate the response. For my own understanding, is there something I am missing in the whole 5ft vs 8ft trap arm length for 2" waste lines? In what case is one vs the other applicable?
    – sil80
    Jun 22, 2021 at 15:54
  • UPC has a table specifying a max trap arm of 5-feet for a 2" drain. My read of your post is that you are under IPC. Jun 22, 2021 at 19:15
  • 1
    Looks like there are differentiations between the code - UPC states 5' max trap to vent, while IPC 2015 states 8' max trap to vent. I am in an IPC 2015 land, so my 7'9" trap arm length should be ok. I thought I was going crazy and misunderstanding definitions within the same code, but the codes are just different.
    – sil80
    Jun 22, 2021 at 19:32

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