The main design parameter for a DRS is flow rate.
Actual flow rate of DRS (SCMH) = (Commercial demand at P1) + (Industrial demand at P2) + (Residential demand at P3)
where, P1-peak hour for the commercial segment,
P2- peak hour for the industrial segment,
P3- peak hour for the residential segment.
All demands are in SCMD.
Designed flow rate of DRS = (Actual flow rate ) * 1.3
Generally, DRS is available in the range of 5000 SCMH to 10000 SCMH. Based upon this flow rate we select the size of pipe, valves and fittings etc. All the DRS should be designed for three-stream (2+1) two active + one standby basis.