Septic Tank Pump-Out Interval

Years between tank pump-outs from the working volume, household size, and a per-capita sludge/scum accumulation rate. A planning estimate -- a sludge-judge measurement and any mandatory state interval govern.

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Formula and source

Allowed accumulation = tank volume x fill fraction; years between pump-outs = allowed accumulation / (occupants x accumulation per person per year).

USEPA Onsite Wastewater Treatment Systems Manual (EPA/625/R-00/008); university onsite-wastewater extension pumping-frequency guidance, by name.

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