Water Supply, Roofing, Stormwater and Rainwater Services
Water supply
Potable supply must be protected from contamination at all times. Understand backflow prevention (air gaps, vacuum breakers, reduced pressure zone devices), the difference between containment and zone protection, and when each applies. Know pressure and flow requirements for fixtures, the purpose of pressure-reducing valves, and why dead legs and undersized pipe cause poor performance. Materials must suit pressure, temperature, and UV exposure; hot lines need insulation and allowance for expansion.
Roofing and stormwater
Roof drainage relies on gutters, downpipes, and stormwater drains sized to design rainfall intensity. Know the difference between eaves gutters and box gutters, the need for overflow provisions, and why downpipes must discharge to stormwater, never to the sanitary drain. Sizing depends on roof catchment area and rainfall intensity; the catchment area includes the roof plan area adjusted for pitch. Traps and silt pits help manage debris.
Rainwater and reuse
Rainwater tanks need first-flush diversion, screens, and overflow to stormwater. Reused rainwater for non-potable uses requires clear labelling, backflow protection, and compliance with local rules; it must never cross-connect with potable supply.
Worked example and traps
Catchment: a roof plan 10 m × 8 m = 80 m². With a 30° pitch, the actual roof surface is larger, but drainage design typically uses the plan area with an intensity factor per the standard. Traps: sizing downpipes on roof surface area rather than plan area; forgetting overflow; connecting rainwater overflow to sewer; and ignoring cross-connection risk in dual-supply buildings. Rule of thumb: every stored-water system needs an overflow that is visible and safely discharged.