A drain collects foul water (from sinks, baths, toilets and washing machines) or surface water (rainwater) from land and buildings within a single boundary. A drain can flow under another property's boundary (known as a lateral drain), a pavement or a highway until it reaches a sewer.
Private sewers are sewers built after 1937 that have not been adopted by the water company. The difference between a drain and a private sewer is that a private sewer joins drains from two or more properties together. Most sewers built before 1937 or those adopted by the water companies are public sewers. Severn Trent Water will be able to tell you if your sewer has been adopted. Some public sewers are found within the boundary of private properties depending on when the sewer and the property were built.
A road gully is a chamber covered with a metal grate or grill at the edge of a highway. It collects and drains water from the highway. Road gullies are the responsibility of Derbyshire County Council.