Influent Structure

  1. Provide 2.5 ft width inlet and 7 submerged orifices with 1"x1" each and maintain velocity in inlet channel larger than 1.0 fps.

    Figue 13. Influent Structure--Pipe discharging in a channel which has series of opening at the bottom.

    Figure 14. Plan of influent structure (The dimension doesn't represent the design in the example)

    Flow depth of inlet channel is,

    V=1 fps, 1mgd=1.547 ft3/s

    That’s ok for the Design Factors of Vchannel>1.0 fps.

Use V=1fps and width <1/2 of tank width

Qp(gal/day): V(ft/s):

W(ft): No. of Tanks:


Recalculate velocity with actual depth

Qp(gal/day) W(ft):

d(ft): No. of Tanks:


  1. Hydraulic head over orifice:
  2. Consider adverse situation and orifice area(na)

    One tank service at Qp=10mgd

    Two tanks service at Qp=10 mgd or one tank for QA,d=5mgd,

    Use the Design Factors to select your own design parameters

    Qp(gal/day): Area of Each Orifice,a(ft2):

    No. of Orifices, n No. of Tanks


  1. Two tanks service at QA,d=2.5 mgd

Go back to previous dialog boxes to calculate Head loss at average flow.

  1. Full-Width Baffle:
  2. 6 inches below water surface, 2 inches below orifice bottom.


    =3.0' - 0.21' - 0.5' + 1'

    =3.3 ft

    size=LxD=25' x 3.3'

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