Construction
Septic Drain Field Calculator
Drain field sizing is dirt math. Faster perc rates mean less trench; slow clay can need 5x the area.
Trench length (ft)
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- GPD
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- Loading rate
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- Area (sq ft)
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FAQ
What is perc? +
Percolation rate — how many minutes for water to drop 1 inch in a saturated test hole. Slow perc means slow drain field.
Engineered system needed? +
If perc is over 60 min/in or there is shallow bedrock/water table, you usually need a mound, aerobic treatment unit, or pressure dose system.