Should an open indoor plumbing pipe be capped or left open?
An open indoor plumbing pipe may be functioning as a purposeful vent for a septic or drainage system, meaning capping it incorrectly could cause drainage issues or trap harmful gases. Homeowners struggle to determine whether these exposed pipes are active vents or safety hazards that need to be sealed.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1leaving the pipe open and adding a screen to keep out debris
- 2installing an air admittance valve
- 3leaving the pipe open and ignoring it
- 4filling the P-trap with water
- 5cutting and capping the pipe
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“This pipe is directly opposite of the kitchen sink. That top part is completely open. When kitchen sink runs you can see the water drain if you look down it. Should that not be capped? The house is on a septic tank (which I’ve never had before) so I didn’t know if this is purposeful like maybe it provides some type of venting or something? Just seems odd.”source ↗
Where this came up
People with this problem also raised
- 3How to fix a sink drain pipe that is too short
- 5Should I reuse an old plumbing drain or replace it?
- 5Slow drip on sewer pipe joint
- 2Do I need to flush the coolant when replacing a cracked radiator?
- 2Should I remove an old mixing valve during a renovation?
- 5Are gutter guards actually worth it with heavy rain?