How does HydroMax Siphonic Drainage Work

HydroMax Siphonic Drainage operates from natural hydraulics inducing a negative pressure in the piping system through the vertical displacement from roof to discharge position.

HydroMax Syphonic Outlets in Gutter A HydroMax™ Siphonic Roof Drainage system utilises the full height of the building to provide the energy to create a powerful siphonic action. A collection of elements combine to create the HydroMax™ Siphonic Roof Drainage System.

The piping system is empty prior to a storm event occurrence. As the rainfall event starts, our unique HydroMax™ Siphonic Roof Drain prevents further air-entry into the pipework system whilst its Anti-Vortex fins also stop Vortex formation.

Our technically advanced HydroTechnic™ analytical design program (with unsurpassed accuracy) is used to calculate the hydraulic conditions and determine the pipework diameters necessary to rapidly fill and prime the pipework system for optimised performance. 

HydroMax™ will utilise significantly smaller pipe diameters than that required in a traditional gravity system.

As the small diameter pipes prime and the water reaches the vertical downpipe, the water accelerates due to the forces of gravity. This acceleration creates the negative pressures that give the system its ‘Siphonic’ title and the forces literally suck the water off the roof until the end of the rainfall event.

The HydroMax™ siphonic roof drain has been developed to provide superior performance during storm conditions. Additionally, the HydroMax™ siphonic drain and HydroTechnic™ pipe sizing software have been tested by HR Wallingford in accordance with the performance requirements of the current European Standard EN 12056-3:2000. 

THE PRIMING STAGES OF A  HYDROMAX™ SIPHONIC SYSTEM 

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The advanced HydroTechnicTM software enables the design engineer to create a system with the correct pipe sizing to ensure the best possible configuration, rapid prime and optimum performance. 

A HydroMaxTM siphonic roof drainage system does not use any moving parts to create the
full bore flow conditions - only hydraulics.

The one-piece inducer on the HydroMaxTM roof drain, seals off air ingress to only permit water
to enter the pipework.

The anti-vortex fins prevent the formation of vortices which would also draw air into the piping. 

Hydromax Siphonic Systems are Self Draining

Being a self-draining piping system, at the start of a rainstorm the pipework is empty as shown above.
As the rain enters the HydroMax roof drain, the tail-pipes will quickly fill and supply water into the horizontal collector pipe.

Hydromax System with Tailpipes primed

The tailpipe will continue to discharge water into the carrier pipe and as more water is supplied to the main carrier pipe will flow in gravity flow with air and water mix in the pipe as shown below.

As the pipe is flat without slope, it is designed to quickly fill up with water, the plug of water then accelerates down the downpipe creating negative pressure and start sucking the water from within the carrier pipe. 

Air Above Water

Gravity Flow

PRIMING STAGE 2

An increase in rainfall rate and the acceleration down the vertical creating suction leads to the water being pulled into plugs that fill the pipe for short lengths. These plugs also push out pockets of air entrapped between the full bore plugs as shown below.

Research at Herriot-Watt University and testing by HydroMax has shown that this flow pattern is typically achieved at 10% to 15% of the design rainfall intensity.

Importantly, at this 10% to 15% of design rainfall rate, self-scouring velocities are achieved -
Ensuring regular self-cleansing of the pipe system.

Plug Flow

Plug Flow

PRIMING STAGE 3.

As the rainfall rate intensifies, the water almost fills the whole of the pipe and any remaining air is carried out in bubbles entrained in the water flow.

Bubble Flow 

 Bubble Flow

PRIMING STAGE 4.

As the design rainfall rate is achieved, no air remains in the pipework, leaving the pipes fully primed to run full bore.

At full-bore flow with high, self-scouring velocities, the HydroMax system is now utilizing the full height of the building to draw water efficiently off the roof.

 

Water fills the whole pipe: Full Bore

Full Bore Flow

Fully Primed HydroMax System

VERTICAL DOWNPIPES

As the air is removed from the piping system the whole system changes from the empty pipe system to a fully primed system with the downpipes also full.

 A gravity downpipe will run with a core of air (most standards or codes limit water to approximately 30% with air taking up 70% of the pipe capacity!)

A HydroMax downpipe will be full and flowing at high velocities.

Based on a single storey building a HydroMax siphonic flow downpipe pipe will drain 10 to 15 times more flow than you would obtain in the same diameter under traditional gravity flow.

In gravity flow the pipe will be a large diameter to accomodate the air core taking up 70% of the pipe volume.

With HydroMax siphonic 100% full-bore flow the pipes are significantly smaller diameter, with high velocities that self-scour the pipes.

All-in-all a really effecient drainage system maximising the carrying capacity of the pipes.

Downpipe Comparison

SAVING IN PIPE DIAMETERS WHILE INCREASING FLOW
HYDROMAX IS THE SIPHONIC ROOF DRAINAGE SOLUTION

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