While all of the above mentioned tariffs consist of only one charge, fixed or volumetric, another possibility is to combine them in a two-part tariff. A two-part water or wastewater tariff usually consists of

• a fixed monthly service charge plus

• a volumetric charge that is based on the actual consumption/ discharge.

There are many variations in the way these two components can be put together. For example, the volumetric charge can be a constant volumetric, a linear increasing or block tariff. In many cases, the fixed charge is rather low and serves as a means to recover the fixed administrative costs of service providing that are unrelated to the amount of water consumed/ discharged (such as costs for meter reading, billing, etc.). They can also be used to recover the investment costs of the utility. The revenues from the volumetric part of the tariff are then meant to cover the operational costs related with provision of the wastewater service.