Reference tables
Look-up charts built from stable conventions — minimum tank size by bedrooms, perc-rate → soil-loading bands, trench & lateral conventions, pressure-tank drawdown factors, the water-hardness scale, fixture flow & per-person gpd, and unit conversions.
Minimum septic tank size by bedroomsCommon minimum septic-tank gallons by number of bedrooms (750–1,500+ gal) as labeled planning bands — your local health department sets the required minimum.Percolation rate to soil-loading-rate bandsHow a percolation-test rate (minutes per inch) maps to a drain-field soil loading rate (gpd per sq ft) as labeled planning bands — the local health department table governs.Effective trench width & lateral-length conventionsEffective drain-field trench width (~3 ft), maximum lateral length (~100 ft) and gravel depth as labeled planning conventions behind the trench-length tool.Pressure-tank drawdown / acceptance factorsPressure-tank acceptance (drawdown) factors by pump cut-in/cut-out setting (20/40, 30/50, 40/60 psi) — the labeled convention behind the pressure-tank sizing tool.Water-hardness scale (gpg ↔ ppm)The water-hardness classification (soft → very hard) in grains per gallon, with the stable ppm ÷ 17.1 = gpg conversion — behind the softener sizing tool.Fixture flow (gpm) & per-person gpd conventionsTypical household fixture flow rates (gpm) and per-person daily water use (gpd) as labeled planning conventions behind the pump-GPM and daily-water-use tools.Septic & well unit conversionsThe fixed unit conversions behind the calculators: 7.48 gal per cubic foot, 27 cu ft per cubic yard, 231 cu in per gallon, ppm ÷ 17.1 = gpg, psi × 2.31 = feet of head.