How does it work? - CRS | Sheffield | Siphonic, P.A.R.S and Conventional Rainwater Disposal Systems

Gravity flow

With low rainfall intensities giving a flow of 10-15%of the design rainfall intensity value, the roof outlet works exactly how it would in a conventional system. During this stage which is defined as "gravity flow" there is an elevated air content in the pipes.

Plug flow

Once the it is between 10-15% and 60% of full bore the water flow is discontinuous and the system will switch from a gravitational flow to a full siphonic action. Air is allowed to be drawn into the piping network which breaks the siphon, this is why the stage is called "plug flow"

Bubble flow

Between 60% and 95% of the full bore flow the pipes are completely full of water, although many air bubbles are still present. This stage is called "bubble flow" and still features high flow velocities thanks to the siphonic effect.

Full bore flow

Once a flow of above 95% is reached the siphonic effect starts completely, the maximum flow rate is reached and no bubbles are inside. This is the "full flow" stage and it does not produce any noise or vibrations.

Bernoulli’s principle

In fluid dynamics, Bernoulli’s principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy. Bernoulli’s principle is named after the Dutch-Swiss mathematician Daniel Bernoulli who published his principle in his book Hydrodynamica in 1738.