Drainage fixtures, blockage materials and symptoms
Drain blockage library
Guidance on common drain blockage materials, the fixtures they affect and the symptoms that can distinguish a local restriction from a problem further along the drainage system.
A slow sink on its own points somewhere different from several fixtures backing up. A gully that overflows only during rainfall raises a different question again. Looking at which outlets are affected, and when, helps narrow down where a restriction or fault may lie.
Affected outlets: one sink or toilet, several fixtures, or an outside drainage point.
Timing: continuous, after another fixture discharges, or only during rain.
Material: suspected wipes, grease, leaves or another known obstruction.
Current condition: slow drainage, backing-up, overflowing wastewater or loss of use.
Reference sources for this library
The references below cover the products, drainage systems and blockage materials used in this library. Manufacturer information describes the named product or system only; it does not establish the condition, suitability or requirements of a particular installation.
How leaves, litter and sediment affect outdoor gullies, and how to distinguish a blocked surface inlet from a restriction or capacity problem further along the drainage system.
A back-inlet gully can receive connected pipework as well as flow at the gully itself. Flooding may come from the inlet, sediment in the gully or a restriction further downstream.
A bottle gully is a trapped external drainage fitting with removable internal parts for access. Flooding may arise within the gully or in the connected drain.
A gully that overflows during rainfall may have a blocked inlet, sediment within the gully, a downstream restriction or insufficient drainage capacity. Visible leaves do not rule out a deeper problem.
