Filed under Cast Iron & Older Homes · By Michael and the team at The Irish Plumber
What the stack vent does
Your main stack runs from the basement up through the house and out the roof. The top section is the vent. It lets air into the drain system so water flows freely, and lets sewer gases escape outside instead of into your home. Without enough air, draining water creates suction that pulls water out of the traps under your sinks and tubs.
Signs of a vent problem
- Gurgling in sinks, tubs or toilets when another fixture drains
- Slow drains throughout the house with no clog found
- Sewer smell indoors, because traps are being siphoned dry
- Toilets that bubble or don't flush strongly
Common causes
- Blockages at the roof: leaves, bird nests, debris, or ice and frost buildup in Ottawa winters
- Corroded or cracked cast iron in older stacks
- Renovations that added fixtures without proper venting
- Undersized or missing vents in older additions
Gurgling drains or a sewer smell?
We'll find out whether it's a clog, the vent, or the stack itself.
How vent problems are fixed
- Clearing the vent from the roof or through a cleanout
- Adding proper venting for fixtures added in past renovations
- Replacing a corroded section of cast iron stack with ABS
- Replacing the whole stack when the cast iron is near the end of its life
In older homes, a gurgling drain is often the first sign the cast iron stack is aging. A camera inspection tells you whether it's a simple blockage or something bigger.