Sidestream Fraction of Recirculation

Expresses the sidestream filter flow as a percentage of the system recirculation rate (typically 1 to 5%).

$$f=\frac{Q_{sidestream}}{Q_{recirc}}\times 100\%$$

Variables

Symbol	Meaning	Unit
f	sidestream fraction of recirculation	%
$Q_{sidestream}$	sidestream filter flow	GPM
$Q_{recirc}$	recirculation rate	GPM

Worked example

With a 12.5 GPM sidestream and 800 GPM recirculation, f = 12.5 / 800 = about 1.6% of recirculation.

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Part of The Blueprint of Water