If the flow velocity is to be 4 FPS and the demand is 15 GPM, what is the minimum size parallel manifold that should be selected?

To determine the minimum size of a parallel manifold based on the specified flow velocity and demand, it is important to first convert the flow rate from gallons per minute (GPM) to cubic feet per second (CFS) because the flow velocity is given in feet per second (FPS).

1 GPM is approximately equal to 0.002228 CFS. Therefore, to convert 15 GPM to CFS:

15 GPM × 0.002228 CFS/GPM ≈ 0.03342 CFS.

Next, using the formula for calculating the cross-sectional area needed to maintain the required velocity:

Area (A) = Flow Rate (Q) / Velocity (V).

Substituting the flow rate and velocity into the formula:

A = 0.03342 CFS / 4 FPS ≈ 0.008355 square feet.

To find the diameter of the pipe that will provide at least this cross-sectional area, we use the area formula for a circle:

A = π(D/2)², where D is the diameter.

Rearranging this formula gives us:

D = 2 * √(A / π).

Substituting the calculated area:

D = 2 * √(0