What should I include in a scope for a hydraulic or stormwater designer?

Summary: Designs how water gets to, around and away from the house: stormwater, sewer, water supply and rainwater tanks.

Why it matters: Poor drainage is one of the most common causes of defects and neighbour disputes. Councils and water authorities often need stormwater plans for approval.

Minimum scope by stage

• Planning (if required): stormwater concept; confirmation of the legal point of discharge; on-site detention (OSD) concept if required
• Building approval: stormwater plan (roof water, downpipes, pits, surface drainage, levels); sewer and water connection layout and levels; rainwater tanks; water authority applications (e.g. building over or near sewer)
• Construction: responses to plumber and builder questions; inspection of stormwater or OSD before backfill where required
• Completion: works-as-executed drawings and certification for stormwater or OSD where council or the water authority requires it

Options

• Rainwater reuse and tank sizing
• Easement or inter-allotment drainage
• Pump-out systems for low sites
• Water-sensitive design or water quality devices

Meetings and site visits: Usually desktop; a site visit for sites that fall away from the street; inspections priced per visit.

Watch-out: Some sites have no direct street discharge. Confirm the legal point of discharge with council early. On some small houses the civil engineer covers this scope. The plumber's compliance certificate is separate from the designer's certification.