How to add a vent when you can't reach the stack
Basement fixtures often lack a connection to a main vent stack, making traditional venting impossible without major demolition to walls and floors. Without a proper vent, drains will gurgle and drain slowly, forcing homeowners to look for alternative solutions like air admittance valves or exterior vents.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1gutting upstairs and downstairs bathrooms to tie into an existing vent stack
- 2going downstream to install an in-wall vent box
- 3adding an air admittance valve under the kitchen sink
- 4installing a vent stack on the exterior of the house for bathroom appliances
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“the contractor who built it did not install any venting in our walls or roof. We did not know we needed this so when we tied together our external plumbing we did not add any venting either.”source ↗
“How can I add venting to this system? I was thinking I could add an air admittance valve under the kitchen sink then a vent stack on the exterior of my house for all of the bathroom appliances”source ↗
“Also piping drawn in blue is beneath my house so it will be near impossible to add vents for every appliance. Please help!!”source ↗
“Figured out yesterday that the reason my tub and sink in the bathroom drain slowly and glug is because there is no connection to a vent stack…”source ↗
“Bathroom is in the basement, so tying into an existing vent stack isn’t happening short of gutting both the upstairs and downstairs bathroom.”source ↗
“Any idea how I would fit an AAV here? Or do I need to go down stream and put one of those in wall vent box things in?”source ↗