Water flows down through the centre of the gully, into a basin and back up towards an outlet pipe connected to the drain. ... This “trapped” water serves to prevent any smells and gases from escaping back out of the drain and into the air.

What is the difference between a gully and a drain?

As nouns the difference between drain and gully

is that drain is a conduit allowing liquid to flow out of an otherwise contained volume while gully is a trench, ravine or narrow channel which was worn by water flow, especially on a hillside or gully can be (scotland|northern uk) a large knife.

What does a drainage gully do?

Drainage gullies – also referred to as gully traps – are ground-level drains that rainwater or grey waste discharge into. ... Drainage gullies are designed to allow waste and stormwater to pass through easily but stop bad odours and rodents from escaping from out of the drains.