Gulley (also spelled ‘Gully’) A gulley in its widest sense is a channel carrying water.
In residential properties, ‘gulley’ usually means the open gulley at the foot of a downpipe which collects water (e.g. rainwater or waste water) discharged from the downpipe and channels it into the underground drains.
Gullies are prone to blockage from debris such as leaves falling into them, as well as water-borne debris such as food. If a gulley collects water from a sink then fat in the water will be deposited in the gulley which can build up and cause a blockage.
Gullies usually incorporate a grating to prevent larger debris getting into the drainage system. Such gratings need to be removed and cleaned from time to time.
Any broken gratings should be replaced, as otherwise larger debris getting into the drains could cause a blockage which would be more difficult to remove.
Covers can also be bought which stop leaves and airborne debris falling into a gulley.
Blocked gullies will result in water seeping into the foundations of a building, so they should be inspected and cleaned regularly.
There are a number of different arrangements for making the connection between downpipes and drains.
If the water discharges into a combined drainage system the gulley should incorporate a trap (i.e. a ‘U’ bend similar to that found in a WC) to prevent smells rising up from the sewers.
This type of gulley is also recommended where the rainwater discharges into a surface water drain. A trapped gulley should always have water in the bottom (in the same way that there is water in the bottom of a toilet bowl.)
If there is no water this might indicate that there is a crack at the base of the gulley, allowing water to drain into the ground near to the foundations where it can cause damage.
Dry gullies should therefore be investigated and replaced if found to be broken.
A building survey will report on any apparent problems with gullies, such as evidence of blockages.
Cleaning gullies out is normally not a difficult task (although rather dirty) but replacing a broken gulley would have to be carried out by a builder.
‘Gulley’ may also describe the channel at the point where two sloping roofs meet, which channels rainwater from both roofs to the gutters.
This is also known as a valley; see separate entry for more information.