How HydroStorm® Works:
From Rainfall to Rapid Roof Drainage
Priming
At the start of a rainstorm, the system is empty. As rain enters the HydroStorm® roof drain, the vertical tailpipes fill quickly, channelling water into the horizontal collector pipe.
Stage 1 - Gravity Flow
- Initially, water flows through the horizontal pipe alongside air in a gravity flow pattern. The system is partially filled and air pockets remain above the water.
Stage 2 - Plug Flow
- As rainfall intensifies, water volumes increase. When water reaches the vertical downpipe, gravity accelerates it downward, generating suction. This creates short “plugs” of water that efficiently pull rainwater along the pipe, pushing trapped air ahead.
- Research and testing show that plug flow occurs at just 10-15% of the design rainfall rate enough to achieve self-scouring velocities, keeping pipes clean without manual maintenance.
Stage 3 - Bubble Flow
- With heavier rainfall, the pipes are almost full and the remaining air forms tiny, entrained bubbles carried along by the water. This bubble flow ensures the system remains efficient even under intense rain.
Stage 4 - Full-Bore Flow
- Once the Outlet Air Baffle prevents any air ingress, pipes become fully primed. Water flows at maximum self-scouring velocity, utilising the building’s full height to create suction and remove water from the roof with unmatched efficiency.
The HydroStorm® Advantage
HydroStorm® Siphonic Roof Drainage isn’t just efficient—it’s smart and engineered to handle any rainfall scenario with confidence.
Flexible Layouts
Reduced pipe diameters and fewer vertical runs allow more flexible building design
Energy-Free Operation
Harnesses building height and water momentum -no pumps required
Reliable Worldwide
Proven performance across commercial, industrial, and complex architectural projects
Self-Cleaning Efficiency
Achieves high velocities even at low rainfall rates, preventing blockages naturally
Maximum Pipe Capacity
Siphonic downpipes can carry 70% more water than gravity downpipes of the same diameter