What is mains water drainage?
Edited
Mains water drainage means that wastewater (from toilets, sinks, baths, etc.) from the property flows into the public sewer system operated by the local water company. If the property is not connected, it may instead use a private system (such as a septic tank, cesspit, or treatment plant). If you are unsure, please contact your conveyancer or a surveyor for assistance.