Hydro-Brake® Optimum vortex flow controls
Flow control and flood protection

Hydro-Brake Optimum

Manage low, moderate and high flows to deliver sustainable drainage from single sites to large networks.

The Hydro-Brake® Optimum vortex flow control provides tailored water quantity management for storm, surface, foul or combined water across a wide range of flows and for a variety of applications.

Precision-engineered to meet site-specific flow, head and storage requirements. Only the Hydro-Brake® Optimum leverages more than 40 years of vortex flow control expertise to deliver exceptional flood protection and sustainable drainage.

Design your Hydro-Brake® Optimum online. Log in or sign up to the free online tool: hydro-int.design

The Hydro-Brake® Optimum vortex flow control provides tailored water quantity management for surface, foul or combined water across a wide range of flows and for a variety of applications.

Self-activated and precision-engineered to meet each site or network's specific flow, head and storage requirements. The Hydro-Brake® Optimum delivers effective protection from upstream and downstream flooding as a part of a sustainable drainage system (SuDS).

With no moving parts and no power requirements, the Hydro-Brake® Optimum provides reliable, low-maintenance, and engineered flood management as part of green infrastructure developments.

Our most popular Hydro-Brake Optimum, the Hydraulic Efficient unit incorporates an adjustable inlet as standard.  This will allow engineers to future-proof their drainage designs with up to a plus or minus 20% change in design flow, should additional developments or urban creep cause an increase in flows, saving the cost of a replacement flow control.    Find out more about the adjustable inlet here.

Hydro-Brake Optimum SHE

A range of alternative fittings and installation options to meet most site configurations are available for Hydro-Brake® Optimum.

Learn more: download the Hydro-Brake® flow control series brochure

Independently assessed, approved and certified

For peace of mind, the performance, strength and durability of the Hydro‐Brake® Optimum has been independently assessed, approved and certified by both the BBA (Certification no. 08/4596) and the WRc Certification no. PT/503/0422) to control stormwater or combined flows.

WRc & BBA Logo for Hydro-Brake® Optimum

Only Hydro-Brake® Optimum:

  • Is individually custom-designed to meet specific site and network requirements
  • Draws on a legacy of more than 40 years of vortex flow control technology
  • Is designed and delivered by the leaders in flow control 
Video file


Get custom-designed, precision-engineered flood protection

Every Hydro-Brake® Optimum flow control is individually designed, sized and precision-engineered to meet the specific requirements of the site, network and environment in which it is installed, enabling engineers to deliver tailored protection against upstream and downstream flooding.

Specify SuDS, LID and green infrastructure projects with built-in protection against storm events, management of everyday surface water runoff and capacity for the future effects of climate change.

You can even design your flow control online with our online design tool.

Built-in future proof adjustability

Standard, Hydraulic Efficient, Hydro-Brake® Optimum units are supplied with an adjustable inlet, allowing post-installation flow adjustments without the need to replace the whole device.  Find out more about the adjustable inlet here.

Deliver small, medium or large-scale sustainable drainage

With a maximum flow of up to 550 l/s (8,717.7 gpm) and a maximum storage area of up to 275 ha* the Hydro-Brake® Optimum provides effective, reliable flow control across a wide range of environments and applications, from small individual plots to large sewer networks, giving designers the flexibility to implement a range of sustainable drainage and green infrastructure projects.

Design with complete freedom

The Hydro-Brake® Optimum provides complete freedom in the response characteristic of the flow control. 

For a given maximum design head and flow, the point at which the vortex begins can be specified, enabling engineers to tailor flow controls to solve even the most challenging requirements.

Independently assessed, approved and certified

Having been independently evaluated, tested, approved and certified by the BBA (Certification no. 08/4596) and the WRc (Certification no. PT/503/0422), customers can be confident that every flow control meets rigorous quality, performance and installation standards.

Meet difficult site configurations

Hydro-Brake® Optimum has options for a range of alternative fittings / installation options to meet most site configurations.

Assumes an average of 2 l/s / 31.7 gpm per ha

Hydro-Brake® Optimum flow controls are self-activating, relying on upstream hydraulic head to generate an air-filled vortex within the middle of the casing. The flow control moves through three distinct phases of operation:

Low Flow

Under low flow conditions the flow control behaves like an oversized orifice. The flow is gentle, with minimal turbulence inside the volute of the flow control or the outlet pipe. As the water level starts to increase above the soffit of the outlet, air becomes trapped in the volute. This exerts a back pressure against the water and begins to restrict the cross-sectional area available for water flow.

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 is the point at which there is sufficient energy within the flow to sustain a stable vortex.

High Flow

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 flow control restricts the flow in a similar fashion to an orifice, but with clear openings up to 600% larger, significantly reducing the risk of blockage.

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 flow control returns to operating in a similar manner to an oversized orifice. This drains the system quickly and more effectively, so that the flood storage reservoir is ready for the next event.

See it in action:

Video file

Performance Characteristics

Maximum flow: 550 l/s / 8,717.7 gpm

Maximum head: 4.0 m / 13.12 ft

Approximate maximum storage area: 275 ha*

*Assumes an average of 2 l/s / 31.70 gpm per ha

> Design your Hydro-Brake® Optimum online - try the online design tool at  hydro-int.design


Custom Performance 

Reduce onsite storage

Matching the Flush-Flo™ point equal to the design point 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.

To help engineers be prepared for the effects of urban creep, changes in regulations or changing climate, Hydraulic Efficient S-type units are now supplied with an adjustable inlet as standard.   This future-proof feature allows flow adjustments post installation without the need to replace the whole device.  A unique triple flow head/discharge curve is generated by the Online Design Tool for these units.  Find out more about the adjustable inlet here.

Limit flow control size

Reducing the Flush-Flo™ point reduces the size of the device, so if the exact available space is known then the Flush-Flo™ point may be tuned to give the most hydraulically efficient performance within the space available. 

Design complex systems

Custom Flush-Flo™ points can be specified, enabling the design of precise ‘complex flow control’ arrangements where the pre-developed hydrology is aligned to the post-developed site.

Low Flows

There are now a variety of industry guidance documents applied at national and regional levels and they are not totally consistent in terms of their stance on minimum flow rates or minimum flow control sizes.

The approaches range from BS8582:2013, which states “controls smaller than 25 mm are possible if protected [from blockage]” up to the advice given by water companies, which can set a minimum acceptable opening size for adoptable flow controls for surface water only systems of >50 mm for protected orifices and >100mm for unprotected orifices.


> To find out more download our white paper, Going with the Flow.


UK 3D BIM Models

> Request a UK 3D model of the Hydro-Brake® Optimum for use with UK Building Information Modelling (BIM)


  • Hydro-Brake Optimum 2024
  • Hydro-Brake Optimum hydraulic efficient SHE future-proof design
  • Hydro-Brake® Optimum mounting options
  • Hydro-Brake® Optimum post-initiation phase
  • Installation of an Hydro-Brake® Optimum pre-fitted into a chamber
  • Conical type Hydro-Brake® Optimum with open bypass door.

How much downstream clearance should I allow?


All vortex flow controls need to maintain a downstream clearance in order to allow the vortex to fully form, and within this clearance no valves, controls or other devices should be installed, and no pipe bends or changes to pipe diameters should be made.

This clearance is typically around 3 m / 9.84 ft or ten times the outlet diameter of the unit, whichever is greater.


Does the unit work under downstream surcharge conditions?


Yes, but an air vent pipe may be required to ensure that the air core can form. 

The flow through a Hydro-Brake® Optimum flow control depends on the size of the unit itself and the differential head of water acting upon it. 

Please contact us for further information.


Why is there a door on the front of the unit?


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 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 mechanism that may contribute to debris being caught around the unit.


What type of maintenance does the unit require?


Maintenance will be dependent on the site, the size and characteristics of the flow control, the nature of the influent and any physical characteristics of any control chamber.


How many flow control units will I need?


Each site has different existing and future flood alleviation and protection requirements, so the size, design and number of flow controls will depend on site-specific design parameters.

We are able to provide design, guidance and advisory support in this area - please contact us if you would like support.

Design your Hydro-Brake® Optimum flow control online

Use our Online Design Tool to precisely engineer a Hydro-Brake® Optimum flow control to meet your specific site requirements. 


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