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Hydro-Brake Optimum

Hydro-Brake Optimum® is an independently accredited, self-activating vortex flow control with no moving parts and no power requirement.  Hydro-Brake Optimum® is used to control the forward flow of water.

Hydro-Brake Optimum Video

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The Hydro-Brake Optimum® is the only vortex flow control that can truly be designed for “absolute fit” to prevent upstream and downstream flooding with the best-possible hydraulic performance.

Inspired by nature and engineered with a perfect curve Hydro-Brake Optimum® is the latest generation of the Hydro-Brake® Flow Control that offers designers and users the versatility and flexibility to precision-engineer a drainage or sewer design for optimum results on every project.

Rather than having to choose from pre-determined sizes with fixed head/discharge ratios, a Hydro-Brake Optimum® can be sized to achieve the perfect hydraulic performance curve. Unlike other vortex flow controls the inlet, the volute and the outlet of the Hydro-Brake Optimum® are all independently configurable, allowing engineers to have complete freedom in defining the response characteristic to achieve the perfect hydraulic performance curve.

As a result, up to a 15% reduction in stormwater storage volumes and savings of up to 50% on overall project costs can be achieved, compared to other vortex flow controls.

With Hydro’s unique technical support services, online Design Tool and inclusion in MicroDrainage®, engineers can ensure every Hydro-Brake Optimum® is perfectly sized to balance flow rates and attenuation, according to project priorities to:

  • minimise upstream surface water storage
  • maximise outlet clearances to prevent blockages
  • build-in a factor to adjust the flow rate for climate change or urban creep post-installation
  • provide a linear head-discharge relationship.

The online Design Tool also allows engineers to export hydraulic modelling data for use with earlier versions of XP software (eg. WinDes®) or other commercial modelling packages.

Guide to Modelling Hydro-Brake Optimum® using WinDes® 2013 or w12 from XP Solutions

Guide to Modelling Hydro-Brake Optimum® using WinDes® w11 and earlier from XP Solutions

The Hydro-Brake Optimum® has been independently certified by both the BBA and WRc giving engineers, installers and adopting bodies confidence in both the performance characteristics of the device along with the durability/ longevity of the product itself.

Surface Water Applications

  • Stormwater Installation pre-installed in a Hydro-Brake® ChamberStormwater attenuation / storage schemes.  
  • Source Control.
  • Sustainable Drainage Systems (SuDS).
  • Retrofit SuDs applications.
  • Flood prevention.
  • Blue roofs.


Foul / Combined Application

  • Installation within a combined sewer.Wastewater treatment plants.
  • Foul / combined sewer.
  • Sewer risk management.

Careful control of inlet flows at treatment plants prevents hydraulic overload of the treatment plant, enabling the treatment devices to work at their designed efficiency, while control of flows within the sewer network helps to eliminate sewer flooding and CSO spills.

The Hydro-Brake Optimum® can be used to balance flows within a foul / combined sewer system and at treatment plant inlet works to make the best possible use of available capacity within the sewer network.


Key Benefits of the Hydro-Brake Optimum® include:

  • Unique tailoring of the full response characteristics of the devices to give the very best vortex based solution to any flow control requirement.
  • Outperforms other vortex flow controls by offering up to 15% reduction in upstream storage, significantly reducing capital expense.
  • Outlets (clearances) up to 20% larger than other vortex flow controls, minimising the risk of blockage and future maintenance costs.
  • Design and performance independently accredited by both BBA and WRc, giving total confidence in product reliability and operation.
  • Option to include adjustable intake to allow for up to 20% adjustment of the flow, future proofing in case of site modification or climate changes.
  • A range of time saving installation options to simplify construction.
  • Accepted by water companies and local authorities across the UK and Ireland.


Hydro-Brake Optimum™ Showing Adjustable Inlet

The Hydro-Brake Optimum® can be configured with an adjustable inlet to allow future changes to the forward flow.



The Hydro-Brake Optimum® allows engineers to have complete freedom in the response characteristic of the flow control.  For a given maximum design head and flow, the Flush-Flo™ point (the point at which the vortex begins to initiate and have a throttling effect) can now be specified.  The unique ability to specify this point allows additional flexibility to the engineer to solve even the most challenging flow control requirements

The ability to dictate the design point and the Flush-Flo™ point has many advantages:

  • Reduction on onsite storage requirement (green line).  Having the Flush-Flo™ point equal to the design point (green line) means that the device will be as hydraulically efficient as possible leading to more water passing through the unit during the earlier stages of a storm, thus reducing the amount of water that needs to be stored upstream.
  • Limit size of Flow Control (blue line) – The Flush-Flo™ point has a direct relationship on the size of unit required.  Reducing the Flush-Flo™ point also reduces the size of the device therefore, if we know the exact space available, Hydro International can tune down the Flush-Flo™ point to the exact setting that still gives the most hydraulically efficient device within the space available. 
  • Custom Flush-Flo™ Points (orange lines)-  Custom Flush-Flo™ points can be specified by the engineer.  This can be particularly important if designing precise ‘complex flow control’ arrangements where the pre-developed hydrology is aligned to the post-developed site.


Graph Showing Head Versus Flow Characteristic Data

Head versus flow characteristic data.

Careful manipulation of the characteristic curve can assist in achieving the best Hydro-Brake Optimum® solution to meet even the most stringent requirements.  Please refer to the Hydro-Brake Optimum® technical design manual for further information.


Hydro-Brake Optimum® flow controls are self-activating, relying on upstream hydraulic head to generate an air filled vortex within the centre of the casing. This air filled core occupies the majority of the outlet restricting the flow. The vortex generates high peripheral velocities which further restrict the flow and create a back-pressure.  This back-pressure restricts the flow to the periphery of the outlet orifice.

The Hydro-Brake Optimum® moves through three distinct phases of operation:

Low Flow (pre-initiation)

Under low flow conditions (pre-initiation phase), the Hydro-Brake Optimum® behaves like an oversized orifice.  The flow is gentle, with minimal turbulence inside the volute of the Hydro-Brake Optimum® or the outlet pipe.

As the water level starts to increase above the soffit of the outlet, air will become trapped in the volute of the Hydro-Brake Optimum®. This will start to exert a back pressure against the water and will begin to restrict the cross sectional area available for water flow.

The peak flow rate at the end of this phase, defined as the Flush-Flo™ point, is the point at which the vortex begins to form.

Low Flow (Pre-initiation) Phase

Uniquely, the Hydro-Brake Optimum® allows this Flush-Flo™ point to be configured to suit the application.

As the water depth continues to increase, a vortex begins to form within the unit and the entrapped air forms the central core.  At first there is not enough energy in the water flow to sustain a stable vortex, so the vortex will continually start to build and collapse.  

The head at the end of this phase, defined as the Kick-Flo® point, is the point at which there is sufficient energy within the flow to sustain a stable vortex.

Transition Phase
Transition phase.

High Flow (post-initiation)

A stable vortex is maintained within the flow control.  High peripheral velocities around an aerated core create a back pressure, which effectively chokes the flow through the outlet aperture.  Following initiation of the vortex, the Hydro-Brake Optimum® restricts the flow in a similar fashion to an orifice, but with clear openings up to 600% larger, significantly reducing the risk of blockage.

High flow (post-initiation) phase
High flow (post initiation) phase.

Drain Down

As the water level subsides, the energy within the flow reduces and the vortex collapses.  Air is drawn into the volute and the Hydro-Brake Optimum® returns to operating in a similar manner to an oversized orifice.
This drains the system quicker and more effectively, so that the upstream network is ready for the next event.



Frequently Asked Questions

Q.  What is a Hydro-Brake Optimum®?

A. A Hydro-Brake Optimum® is a no-moving parts, self-activating vortex flow control.  When the upstream water level reaches a suitable level the water entering the unit spins within it.  This causes the formation of an air-filled core which takes up a significant proportion of the outlet of the unit.  Water discharges around the periphery of the outlet from the Hydro-Brake Optimum® only which enables the use of a significantly larger outlet than if a simple orifice was used.  The outlet cross-sectional area can be significantly greater than that of other flow controls required to meet the same head / discharge condition.

Q. Are all vortex flow controls the same?

A. NO! The performance characteristics of the Hydro-Brake Optimum® are unique and have been independently accredited by the BBA and WRc.  We pride ourselves on being able to deliver the very best hydraulic performance from our products, the value of which is realised through the efficient design of stormwater and wastewater infrastructure. 


Switching from a Hydro-Brake Optimum®  to an alternative vortex flow control device may remove added value already factored into the design.  This can lead to inadequate storage capacity onsite, resulting in:    

  • Increased flood risk (onsite and downstream).
  • Premature flooding of the storage facility.
  • Unauthorised over discharge from the site

The smaller openings and outlets on other products can lead to an increased risk of blockage, and the inferior materials used by some suppliers can lead to structural failure resulting in installers having to spend a lot of time and money rectifying problems and repairing their damaged reputation


Q. How much maintenance does a Hydro-Brake Optimum® require?

A. Quite simply, this is site-dependent. It depends upon the size of the Hydro-Brake Optimum® itself (the larger the unit the less the likelihood of a blockage occurring), the nature of the influent (for example a unit of a given size would be more susceptible to blockage were it placed on a foul system than on a purely surface water system) and physical characteristics of the control chamber itself (adequate benching is essential).  We have minimum recommended sizes for use within surface and foul water systems (contact Hydro for more information).

Q. Why is there a door on the front of the unit? Can I open this to increase the flow rates?

A. The door is intended to allow an emergency drain down of the manhole chamber or tank in case of a blockage at the inlet of the Hydro-Brake Optimum® unit.  It can be operated from the surface, allowing the chamber to be emptied prior to freeing the blockage from the inlet of the unit.  On release of the pull cable, the door will close under its own weight and does not require any complicated mechanism that may contribute to debris being caught around the unit.

The door should only be opened in the event of a blockage and must be closed following maintenance.  Opening the door during normal operation will prevent the unit from operating as a vortex flow control and will pass more flow than permitted under the unit design.  This could constitute a downstream flood risk.

Q. Do they work under downstream surcharge conditions?

A. Yes, but an air vent pipe may be required to ensure that the air core can form.  The flow through a Hydro-Brake Optimum® is dependent upon the physical size of the unit itself and the differential head of water acting upon it.  Please contact us for further information

Q. How much clearance must I allow downstream before I can fit another valve, control or device, put a bend in the pipe or change pipe diameter?

There is a requirement of all vortex flow controls to maintain a downstream clearance to allow the vortex to fully form.  This clearance is typically around 3m, or 10x the outlet diameter of the unit (whichever is the greater).


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As the first phase of Edinburgh City Council’s 21st Century Homes project for much-needed affordable housing, the Gracemount development is showcasing sustainable construction.

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The Highways Agency’s £375 million upgrade to create 28 kilometres of new dual carriageway on the A46 in Nottinghamshire is using a Sustainable Drainage solution combining natural and engineered techniques to achieve pre-development surface water runoff in a sensitive location.

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A pioneering drainage scheme on a Hampshire housing development, acclaimed as a national example of good practice, was only made possible by 18 of the country’s best-kept SUDS secrets.

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South Lanarkshire College is moving from three separate campuses to one purpose built site on the Scottish Enterprise Technology Park in East Kilbride. Attenuation of stormwater runoff from the new building... 

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As part of the flood alleviation programme for the main street of the pretty Leicestershire village of Worthington, Severn Trent Water designed a 310 m3 stormwater storage facility. 

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Environmental performance is a priority for developers of the prestigious new Meltonwest Business Park on the rural outskirts of Hull, who have used Hydro-Brake® Flow Control technology to engineer a natural solution to surface water drainage.

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Behind the steep, tourist-beloved streets around the cliffs and beaches of St Ives, Cornwall, lies the infrastructure that the town’s residents use all year round.

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General Arrangement of Hydro-Brake Optimum® for Surface Water - CAD Format

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General Arrangement of Hydro-Brake Optimum® with Adjustable Intake, for Surface Water - CAD Format

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General Arrangement of Hydro-Brake Optimum® with Adjustable Intake, for Surface Water - PDF Format

Download File

General Arrangement of Hydro-Brake Optimum® for Surface Water - PDF Format


Guide to Modelling the Hydro-Brake Optimum® using Micro Drainage from XP Solutions


Guide to Modelling Hydro-Brake Optimum® using WinDes® 2013 or w12 from XP Solutions


Guide to Modelling Hydro-Brake Optimum® using WinDes® w11 (and earlier) from XP Solutions


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Pick a flow control to suit your project and budget.



Technical information for design.


Not all vortex flow control systems are the same.

Hydro-Brake Optimum® - There is no equivalent.


Nature's Perfect Curve

Hydro-Brake Optimum®  - There is no equivalent


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