GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Airtighting a drain to daylight?

Mark Harrison | Posted in Green Building Techniques on

We are building a reasonably airtight house.

We plan to install a floor drain with the discharge set up as drain-to-daylight.  I am concerned the the trap might not always have water in it, which would create an air leak. 

Is there a practical way to achieve a reliable air barrier for this drain?  (I am thinking of something like a spring-loaded flapper valve at the daylight end . . . )


GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Malcolm Taylor | | #1

    Several companies sell a back-flow preventer that works as you describe. One is the (unfortunately named) Rectorseal:

  2. thrifttrust | | #2

    Self priming traps are available that periodically introduce a small amount of water into the trap.

    Douglas Higden

  3. Scott K | | #3

    Our drains to daylight don't have P traps. Not exactly sure why, but I had the same concern with our 3 garage drains to daylight. I used these which are similar to the "Sure Seal" product above. We aren't living in our house yet, so I can't speak to their effectiveness, but it appears they will work well.

  4. Expert Member
    Malcolm Taylor | | #4


    P-traps are typically used on drains connected to sewer systems to stop gas from venting into the house. Floor drains to daylight often don't have P-traps, although it's a good idea both to stop pests using it as an entry point, and for air-sealing where that matters.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |