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I am looking to add a shower to my current half bath.

I plan on running the shower drain line to the existing toilet waste line.

My question is:

Do i need to run a separate vent line from the shower line to the existing vent or am i good just adding the drain line?

1 Answer 1


If the distance is less than 5-6’ horizontally from the vent to the new drain normally a single vent will be enough. I have seen contractors double this length on 4” drain lines when the new 2” line ties into a 4” drain

  • Thanks for the quick reply! The addition of the shower will bring the overall width of the bathroom to 6.5 feet so 5-6' sounds do-able. Is this measured from the vertical portion of the vent of where it ties to the toilet drain? if i can keep it under the 5-6' no new vent line is needed correct?
    – chris
    Feb 25, 2020 at 21:06
  • Yes I think it is 6’ . Even though we built close to a hundred houses I don’t remember the inspector ever checking even on remodels.
    – Ed Beal
    Feb 25, 2020 at 21:36

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