The First Draw of the Morning: Overnight Stagnation Inside the Filter Housing, the Spike It Produces, and the Flush Volume That Clears It

SIMULATED, NOT MEASURED. Overnight stagnation in a 0.6 L filter housing raises counts from 3 to 65 CFU/mL in 8 h; the first 250 mL drawn averages 53 CFU/mL and 0.5 L of flushing clears the spike. A passive first-draw divertor design and a printed flush rule are specified. Nothing was built or field-tested.