The priming process… How does siphonic work?
At the initial and final stages of rainfall or during low-level rainfall intensity, the characteristics of the siphonic system are similar to a gravity rainwater system; air can enter along with water. The flow pattern will perform as gravity flow.
When rainfall increases, the flow pattern changes into a Plug flow stage, in which the pressure driven is close to atmospheric pressure. The water fills up with hydraulic plugs inside the pipe. Self-cleaning action starts to occur.
The water rapidly fills up the pipe, but the flow pattern still carries the air bubbles inside, driven by atmospheric pressure.
Full Bore Flow
During heavy rainfall, the system will become fully primed. The pipe system becomes full of water and de-pressurized; below atmospheric pressure. The water is driven with high velocity, allowing the system performance to reach its optimum designed capacity.