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.
Guide information
Whether flooding begins at the gully surface or when a connected waste pipe discharges.
Whether water clears after use or remains backed up.
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.
Guide information
Whether debris or standing water is visible within the gully.
Whether the connected drain also shows slow flow or standing water.
A rainwater downpipe carries roof water to the drainage system. Water escaping at its base during rain may indicate a blocked connection or a problem further downstream.
Guide information
Whether water escapes only during rainfall and how quickly it begins.
Whether nearby gullies or other rainwater connections are also affected.
A rodding eye is a drainage access point used for inspection or maintenance. It provides access to a drain run where there may be no inspection chamber.
Guide information
Where the rodding eye sits in relation to the affected drain run.
Whether other access points show standing or freely flowing wastewater.
