Actually, you are probably better off leaving the filter in place for a longer period of time as it is a depth filter. Depth filters get more efficient with use as the particles start to pile up on the filter media and therefore reduce the porosity of the filter to filter finer and finer particles. Obviously, there is a point in time where the flow, pressure, etc. dictate change, but without a pressure gauge on each side of the filter to give you pressure drop, or a flow meter, you just have to go by instinct. Anybody ever actually instumentate or otherwise run tests on this?

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