Overview
A 9 storey over double basement building with large & small terrace areas.
The Challenge
To segregate rainwater from green roof and hard roof areas into attenuation tanks and rainwater harvesting tank.
The Solution
RTC Design Team worked closely with Architects & Clients of this project to develop a functional and effective combined Siphonic & Gravity roof & terrace rainwater drainage system. The systems were designed to cater for design rainfall intensity of 162mm/hr in accordance with BS EN12056-3:2000. The drainage systems consisted of a parallel arrangement to separate green roof areas to attenuation tank and hard roof areas to drain only into the rainwater harvesting tank. It was critical to avoid contamination of the rainwater harvesting system.
Result
Siphonic drainage was most advantageous on the larger roof areas where possible, mainly as smaller pipework was used in congested ceiling spaces, Siphonic pipework is laid almost horizontal in congested ceiling spaces. Siphonic pipework is easier to coordinate with other services. Gravity drainage was used on areas where roof areas were too small to develop a siphonic flow. In conclusion, the system was designed so that both the rainwater harvesting tank & the attenuation tank were receiving rainwater via both siphonic & gravity systems and no cross contamination was incurred.
All drainage pipework was insulated for thermal and acoustic protection as required
