Plumbing a granny flat: sewer, water and hot water

What sits under the backyard, how a granny flat connects to sewer and water, hot water choices, stormwater and the paperwork, for Sydney homeowners.

A plumber answers 24/7.

Key takeaways

Find out what is under the yard first. Sydney Water must approve plans to build or dig near its pipes, and nothing can be built over a pipe in its easement.
The flat's lowest fixture has to drain to the connection point, and the overflow relief gully must stay at least 150 mm below the lowest connected fixture.
A new hot water service needs a temperature control device limiting outlets to 50°C, and the tank must store water at 60°C to avoid Legionella growth.
If you plan to rent the flat and charge for water usage, it must be separately metered and meet the water efficiency rules.