The system carrying waste water from domestic, commercial and industrial premises for treatment at the sewerage works. Public foul sewers are the responsibility of the sewerage undertaker (usually the water companies). These will be recorded on a map of public sewers held by the sewerage undertaker or they are privately owned and maintained by landowners. Connections from individual or groups of properties to the main sewer are generally the responsibility of the property owners.
You can contact either Severn Trent or United Utilities depending on the location of the flooding.