When a toilet flushes or a stack carries a slug of water, air must move to fill the space behind it. Vents supply that air. Without adequate venting, negative pressure siphons water out of traps — and with it goes the barrier holding sewer gas out of the building.
Gurgling fixtures and intermittent sewer smells are the classic signs of a venting problem or a blocked vent.
Balances air pressure in drains to protect trap water seals.
Extending through roofs, or as air admittance valves in some modern installations.
A CCTV drain inspection is the standard way to confirm whether this is what's happening in your pipes: the camera shows the condition on screen, a locator pinpoints the exact position and depth, and you get a recorded report before any repair decisions are made.
A CCTV drain inspection shows exactly what's happening inside your pipes — no guesswork.