Many industrial effluents are discharged to public sewers and are treated in admixture with domestic sewage. The treatment works provides a service, therefore, to industry. The treatment works manager is under the constraint of environmental restrictions on effluent and sludge disposal and the constraint of keeping costs down. Inevitably these constraints are passed onto the industrial discharger. It is very important that the industrialist is treated like a customer and understands the reasons for the constraints. The paper reviews the nature of the services and constraints. It draws on the author's experience in providing a regulation and treatment service to over 2000 industrialists.