Public vs private

A public sewer is the water authority's responsibility. A private drain belongs to one or more homeowners. The legal regime, and the agreements you need, depend on which it is.

Shared drainage

A drain serving more than one property is usually a public sewer post-2011 transfer. Older properties often still have ambiguous private drains. Check before building over.

Why it matters

Building over the wrong type of pipe with the wrong agreement creates enforcement exposure and resale headaches. Five minutes of checking now saves months later.