Changes

*proprietary low flow devices.  

*proprietary low flow devices.  

Where either device may be installed, a weir is recommended over an orifice, as they are less susceptible to blockage under freezing conditions.   

Where either device may be installed, a weir is recommended over an orifice, as they are less susceptible to blockage under freezing conditions.   

==Weirs==

==Weirs==

==Low flow devices==

==Low flow devices==

Vortex valves have a unique head/discharge relationship. Flow is directed tangentially into the volute to form a vortex that reduces the design peak discharge flow rate from the Vortex Valve far below an equivalent diameter simple orifice.  

Vortex valves have a unique head/discharge relationship. Flow is directed tangentially into the volute to form a vortex that reduces the design peak discharge flow rate from the Vortex Valve far below an equivalent diameter simple orifice.  

*Under low flow conditions, water passes through the valve with negligible pressure drop.

* Under low flow conditions, water passes through the valve with negligible pressure drop.

* Under high flow conditions, a vortex flow pattern develops within the device creating an air filled core. This phenomenon restricts and throttles flow through the device, creating a back pressure in the device immediately upstream of its discharge. During high flow rates, a vortex valve with a relatively large outlet opening performs similarly to a conventional orifice with a much smaller outlet opening; however, debris that might clog a smaller orifice is able to pass through the Vortex Valve because of the relatively larger flow path opening.

* Under high flow conditions, a vortex flow pattern develops within the device creating an air filled core. This phenomenon restricts and throttles flow through the device, creating a back pressure immediately upstream of its discharge. During high flow rates, a vortex valve with a relatively large outlet opening performs similarly to a conventional orifice with a much smaller outlet opening. However, debris that might clog a smaller orifice is able to pass through the Vortex Valve because of the relatively larger flow path opening. The relatively large opening also makes vortex valves less prone to complete clogging from ice formation compared to an orifice of similar specification.<ref>Contech Engineered Solutions. (2018). Vortex Valves. Retrieved March 15, 2018, from http://www.conteches.com/products/stormwater-management/stormwater-flow-controls/vortex-valves#tools</ref>

==Proprietary links==

==Proprietary links==