• HydroStyx Discharge Brake
HydroStyx® Discharge Brake

Delays discharge and activates unused sewer volume

The Challenge

Mea­sures to pro­tect prop­er­ties from flood­ing are nec­es­sary but often expen­sive. The com­mon method to atten­u­ate flows is with the con­struc­tion of stor­age tanks to absorb the peak flow. Because of the huge invest­ment costs involved, local drainage under­tak­ers are often unable to realise such con­struc­tion mea­sures. Action is also called for when old sew­ers in an estab­lished urban area are over­bur­dened by con­nec­tion to new devel­op­ment. The pro­vi­sion of large atten­u­a­tion struc­tures with­in old­er parts of the urban area are fre­quent­ly not pos­si­ble due to lack of space.

The Solution 

A sew­er sys­tem usu­al­ly has large amounts of unused stor­age capac­i­ty since it was designed to cope with peak flows. The HydroStyx® dis­charge brake allows this hid­den cap­i­tal to be uti­lized. Dur­ing heavy rain, the HydroStyx® dis­charge brake allows the free sew­er vol­ume to be used as stor­age. The flow in the trunk sew­er is reg­u­lat­ed to enable unused vol­ume to be used as atten­u­a­tion. Hydro-Styx® dis­charge brakes are installed with­in cham­bers along the length of the sew­er to form a cas­cade. A cal­cu­lat­ed Pass For­ward Flow (PFF) is allowed to flow down the sew­er sec­tion. When the storm flow rate increas­es, the brake caus­es the flow to sur­charge upstream. The debris in the water sink and are trans­port­ed to the treat­ment plant. As the stor­age vol­ume is used, the com­bined water flows over the crest of the brakes and the sew­er regains full capac­i­ty. The retained water con­tains few­er pol­lu­tants, the dis­charge hydro­graph shows that the storm peaks are atten­u­at­ed reduc­ing the down­stream flood risk. Expen­sive sew­er enlarge­ment or atten­u­a­tion tank pro­vi­sion may not be nec­es­sary as the exist­ing sew­er vol­ume can now be mobilised.

The design of the HydroStyx® dis­charge brake requires qual­i­fied engi­neer­ing cal­cu­la­tions of the sew­er net­work. We can rec­om­mend use­ful soft­ware and sup­ply you with com­pe­tent personnel.


  • saves on con­struc­tion and invest­ment by acti­vat­ing avail­able stor­age vol­ume in sew­er channels
  • replace­ment of sew­ers no longer necessary
  • few­er basins required
  • main­te­nance-free

The Advantages

  • dis­charge peaks are evened out
  • dis­charge flows are decelerated
  • over­flows are reduced
  • treat­ment plant oper­a­tion is optimised
  • effec­tive use of sew­er net­work volume
  • hydraulic and eco­log­i­cal stress­es are avoided
  • no elec­tric­i­ty required – exter­nal energy-free
  • robust, stain­less steel construction
  • retro­fit in any shaft possible
  • para­me­ters adjustable
Steinhardt HydroStyx