Septic Tank & Drain Field Sizing Calculator
Size septic tanks, absorption fields, and pump chambers based on bedroom count, soil percolation, and local health codes
Source-aware septic planning screen for organizing preliminary onsite wastewater questions. Enter bedroom, flow, soil/perc, water-table, bedrock, trench, and system-type prompts to review local tank, drainfield, pump-chamber, mound, ATU, reserve-area, setback, and cost rows. The output is not a permit design, public-health approval, installer instruction, soil report, product certification, or substitute for state/county health-department and qualified designer review.
Review soil assumptions near the drainfield site
Soil Bearing Calculator →Screen DWV prompts feeding the septic system
Plumbing DWV Sizing Calculator →Screen the well pump serving the home
Well Pump Sizing →Screen pump energy-cost prompts for a lift station
Pump Energy Cost Calculator →How It Works
-
Enter Dwelling Flow Prompts
Enter bedroom count or a manual daily-flow prompt. Replace local 150 GPD/bedroom and garbage-disposal assumptions with the current local design-flow rule, dwelling plan, fixture use, water-use records, and permit basis.
-
Enter Site Evaluation Prompts
Select a soil/perc prompt and enter water-table, bedrock, and trench-width prompts. Actual suitability requires site-specific soil morphology, perc testing, seasonal high-water evidence, slope, floodplain, and replacement-area review.
-
Select System Type Prompt
Choose conventional, pressure, mound, or ATU prompts only to expose source gaps. Product listings, NSF/ANSI or local approval, dose controls, maintenance contracts, inspections, and local rules control final system selection.
-
Review Local Sizing Rows
Review tank, absorption area, trench length, pump chamber, mound fill, reserve area, and cost prompts. Treat high-water, bedrock, fast/slow perc, disposal, and ATU flags as reasons for qualified review.
-
Check Source Warnings
Use the visible EPA/NSF source pointers and unresolved gaps to prepare questions for the designer, sanitarian, soil scientist, installer, and health department.
-
Export a Review Worksheet
Export a source-aware worksheet for internal planning. It is not a permit submittal, stamped design, health-department approval, product certification, or installation instruction.
Built For
- Homeowners organizing septic questions before contacting the local health department
- Designers and installers collecting source gaps before formal site-specific design
- Real estate teams screening rural parcel questions without treating output as buildability proof
- Contractors estimating planning ranges before bids, permits, and inspection requirements
- Owners comparing conventional, mound, pressure, and ATU prompts before qualified review
Assumptions
- Daily wastewater flow uses a local 150 GPD/bedroom prompt unless the user enters a manual planning value.
- Soil and perc rows are source prompts and not a verified site evaluation.
- Water-table, bedrock, setback, slope, reserve-area, and permit requirements remain unresolved.
- System type is a planning prompt for residential domestic wastewater only.
Limitations
- Does not determine local-code compliance, permit approval, system feasibility, repair acceptability, or drinking-water safety.
- Does not model full hydraulics, distribution network, pump controls, dosing frequency, elevations, alarms, or maintenance contracts.
- Does not replace soil morphology, perc testing, hydrogeologic assessment, product listing, or inspection.
References
- EPA Types of Septic Systems source pointer
- EPA Septic Systems and Drinking Water source pointer
- EPA Onsite Wastewater Treatment Systems Manual source pointer
- NSF residential wastewater treatment system certification source pointer