Drainage interceptors or drain separators are a defence to stop contaminants from entering surface water drains. Also referred to as petrol interceptors or oil separators, they are tanks installed within drainage pipework designed to collect and keep hold of contaminants. For example, petrol and oil that wash into the surface water drain during rainfall.
The purpose of a drain interceptor trap ensures contaminants do not flow into the main surface water sewers. They are essential to control contaminants in water such as oil or petrol and various other pollutants from making their way into the main sewer line.
Typically, a drain interceptor is found in commercial or industrial sites like petrol stations, car parks, production/manufacturing areas and storage facilities, where water contamination is more likely to occur.
Drain interceptors are used to remove contaminants from surface water before it reaches the main sewer system. This is done through a series of tanks or chambers, the surface water from roads and car parks flows into the first chamber which is vented to remove odours and gases safely. The interceptor is designed to allow heavy solid contaminants to fall and settle at the bottom of the tank, while lighter oils rise to the top. The remaining water travels through the system and is discharged to the main sewer system.
There are several types of interceptors; the two main types are full retention interceptors and bypass interceptors.
Full retention interceptors are designed to be used in high-risk areas. The purpose of an interceptor like this is to treat the full flow of water passing through the interceptor. These are usually in place in high-risk contamination sites such as petrol forecourts, fuel depots, manufacturing plants and high-flow traffic areas.
Bypass interceptors are used where there is an acceptable risk of not providing full flow treatment, such as car parks and roadways. During periods of heavy rainfall, the interceptor treats the initial volume and then allows a percentage of the rain to bypass the treatment section of the interceptor.
