Septic LPP Squirt Head for a Target Orifice Flow
The inverse of the septic-lpp-orifice tile: the squirt head (residual pressure) that produces a target per-orifice discharge, h = ( Q / (19.63 Cd d^2) )^2, with squirt pressure = h x 0.433 psi/ft. A 0.25 in orifice at Cd 0.6 delivering 1.28 gpm needs about a 3.0 ft (1.3 psi) squirt head. Flags whether it lands in the LPP 2.5-5 ft band. This is the residual at the orifice; the pump TDH adds friction and lift. The permitted onsite design governs.
Formula and source
h_ft = ( per_orifice_gpm / (19.63 x Cd x d_in^2) )^2, the inverse of Q = 19.63 Cd d^2 sqrt(h); squirt pressure = h x 0.433 psi/ft.
Standard orifice-discharge equation, solved for the head; university onsite-wastewater extension low-pressure-pipe design guidance, by name.
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