Pennsylvania septic rules
Pennsylvania septic tank size & cost
Pennsylvania has no size table — it has a formula. A typical new 3-bedroom system in Pennsylvania runs about $7,600–$12,100 installed by our line-by-line estimate. Below: the state's actual size rule, the full table, and where every number comes from.
Rule: 25 Pa. Code §73.31(a) (capacity) and §73.31(b)(4) (compartments) · Administered by Pennsylvania Department of Environmental Protection (Act 537) · Read the official text · Checked 2026-11-08
Pennsylvania's rule, in plain words
Pennsylvania has no bedroom table at all. The code assigns a design flow by bedrooms, then converts flow to tank capacity with a formula — the numbers below are worked from the code's own formula, not copied from a chart.
Look for a Pennsylvania bedroom-to-gallons table in the official code and you won't find one, because §73.31 works differently: the code assigns a design flow (400 gpd for up to three bedrooms, +100 gpd per bedroom after that) and converts flow to capacity with a two-part formula, with a 900-gallon floor under everything. The numbers in our table are worked from that formula, and the calculator runs the formula itself.
Two Pennsylvania traps: the design flows already include garbage grinders and laundry, so no disposal add-on exists; and multi-compartment construction is mandatory, with the first compartment between one and two times the second.
The Pennsylvania size table
| Bedrooms | Design flow (gal/day) | Minimum tank (gal) | With garbage disposal |
|---|---|---|---|
| 1 | 400 | 900 | 900 |
| 2 | 400 | 900 | 900 |
| 3 | 400 | 900 | 900 |
| 4 | 500 | 1,250 | 1,250 |
| 5 | 600 | 1,400 | 1,400 |
| 6 | 700 | 1,550 | 1,550 |
Garbage disposal: No add-on: Pennsylvania's design flows already include garbage grinders, laundry, dishwashers and water softeners (§73.31(a)(2)). Anyone who multiplies a Pennsylvania tank by 1.5 is inventing it.
Permits are issued by your township's Sewage Enforcement Officer, not by the state.
DEP has a draft Chapter 73 revision circulating (2025, not yet law) — we re-check this page when it lands.
Check your Pennsylvania home
State minimum — your county can require more. Estimate this system's cost →
What a Pennsylvania system costs
Our estimator prices a conventional 3-bedroom system in Pennsylvania (typical-cost area, 900-gal tank) at $7,600–$12,100 installed, assembled from a soil test, the permit, the tank at published prices, drainfield material, fittings and labor. Build your own estimate →
How Pennsylvania compares (3-bedroom minimum)
Full ten-state chart: septic tank size chart.
Other states we've checked
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