Tank size, drain field length, stone or chambers, and cost from bedrooms and a perc test.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ A percolation test and a permit from your local health department or on-site sewage authority are required before any septic system is designed — this calculator estimates materials from typical code tables, not a site-specific engineered design.
| Drainage | $1,592–$2,155 |
| Plumbing & Heating | $1,279–$1,731 |
| Membrane & Fabric | $204–$276 |
| Total | $3,076–$4,161 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Give the Septic System Builder your bedroom count and the percolation rate from a soil test and it sizes the whole system the way a code table does: the septic tank capacity, the drain field area from your soil's long-term acceptance rate, and how that area splits into trenches or gravelless chambers. It handles both gravity and pump-dosed distribution, since a field sitting uphill of the tank needs a pump chamber and control panel the gravity case never touches.
It also builds the full materials list around that sizing — distribution box, effluent filter, perforated pipe or leaching chambers, drainfield stone, filter fabric, and the access risers and lids needed to reach grade from however deep the tank sits. This is a planning estimate for budgeting and prep, not a substitute for the percolation test and permit review your local health department requires before design.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Have a licensed soil evaluator run a perc test and file for a permit with your local health department before anything else — the test result is what actually sets your drain field size, and most jurisdictions require sign-off before installation.
Convert bedroom count into a design flow in gallons per day, then pick the minimum tank capacity your code table requires for that flow, adding capacity if a garbage disposal is in use.
Divide the design flow by the acceptance rate your perc test result maps to, giving a total absorption area in square feet that becomes trench or chamber footage at your chosen width.
Split the total footage into runs no longer than code's gravity-distribution maximum, keeping every setback — well, property line, surface water, foundation — clear on the site plan.
Dig the tank pit to the required depth, set the tank level on a stable base, and connect the inlet from the house and the outlet toward the distribution box.
Set the D-box level so it splits flow evenly to every trench or chamber run, then lay perforated pipe in stone (or connect chamber sections) at a slight, even grade.
Where the field can't gravity-flow, install the pump chamber, effluent pump, and control panel with a high-water alarm on a dedicated circuit wired by a licensed electrician.
Set risers and lids over the tank and D-box so future pumping doesn't require excavation, then backfill and restore the surface, keeping heavy vehicles off the field permanently.
Equip the job
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Garden & Yard
Answers
Tank size is set primarily by bedroom count, not by how many people actually live there, because bedrooms are the code's stand-in for peak occupancy. Typical minimums run 750 gallons for one or two bedrooms, 1,000 for three, 1,250 for four, and 1,500 for five, stepping up from there — with many codes adding another 250 gallons of capacity if a garbage disposal feeds the system, since it increases the solids load the tank has to settle out before effluent reaches the drain field.
A perc test measures how many minutes it takes water to drop one inch in a test hole, and that rate sets a long-term acceptance rate in gallons per square foot per day — faster-draining soil (a low minutes-per-inch number) accepts more effluent per square foot, so the field can be smaller, while slow, clay-heavy soil needs much more area for the same house. That acceptance rate divides into your design flow (gallons per day, from bedroom count) to get the total absorption area, which then converts into trench feet at whatever width you're digging.
Gravity distribution works whenever the drain field sits below the septic tank outlet with enough fall to flow downhill the whole way, and it's simpler and cheaper since there's nothing electrical to maintain. A pump-dosed system is required when the field is level with or above the tank, when the field is large enough that a single gravity dose wouldn't distribute evenly across it, or when local code mandates timed dosing — it adds a pump chamber, a submersible effluent pump, and an alarmed control panel that needs a dedicated circuit.
Both are sized to the same absorption area and both are code-accepted in most jurisdictions, so the choice usually comes down to local stone cost and installer preference. Pipe-and-stone is the traditional build — perforated pipe bedded in washed drainage stone under a filter fabric cap — and tends to be cheaper where stone is locally abundant. Gravelless chambers skip the stone entirely with arched plastic units that create their own void space, which is faster to install and lighter to haul in areas where stone has to be trucked in.
Most codes require at least 100 feet from a drinking water well, roughly 10 feet from property lines, and 50 feet or more from a pond, stream, or other surface water, plus clearance from the house foundation, a swimming pool, and large trees whose roots can invade pipe joints. These numbers vary by state and by county, and some slow-soil or high-water-table sites need larger setbacks or an entirely different system type — always confirm the exact numbers with your local health department before finalizing a layout.
Most residential tanks need pumping every 3 to 5 years, sooner for smaller tanks serving more people or households running a garbage disposal, which adds solids faster than the tank can digest them. The effluent filter at the tank outlet should be rinsed off roughly once a year between pumpings — a clogged filter is one of the most common causes of a backed-up system, and it's a five-minute job compared to a pump truck visit.