Septic Sizing Plumb
Tank & Drainfield Calc
About
Calculate septic tank size and drain field area based on occupancy, flow, and soil percolation rates. Supports various soil types and provides recommendations for septic system design and permitting. Works offline for on-site use.
What's New in Septic Sizing Plumb
1.0.5
June 12, 2026
What's new: - Safety: percolation slower than 60 min/inch is flagged "not suitable for a standard absorption field" instead of silently sizing at the clay rate - Listing references corrected to the commonly adopted state/private-sewage tables
MoreIn-App Purchases
$2.99
Pro Unlock
No ads, unlimited history, PDF export, dark theme.
Developer apps
FAQ
What is the minimum tank size Septic Sizing Plumb calculates?
Septic Sizing Plumb calculates minimum septic tank sizes starting from 1,000 gallons for up to 3 bedrooms. For 4 bedrooms, it calculates 1,250 gallons, and for 5 bedrooms, 1,500 gallons. Additional bedrooms add 250 gallons each.
How does Septic Sizing Plumb calculate drain field area?
The app calculates drain field area based on the soil percolation rate. It uses application rates per square foot per day for different percolation speeds, flagging rates slower than 60 minutes per inch as unsuitable for standard fields.
Can I use Septic Sizing Plumb without an internet connection?
Yes, Septic Sizing Plumb works 100% offline. This allows you to perform calculations directly on the job site without needing an internet connection.
What soil types does Septic Sizing Plumb support?
Septic Sizing Plumb supports 5 soil types, ranging from gravel/coarse sand and sand to sandy loam, loam, and clay loam. It includes typical percolation rates for these presets.
What are the benefits of the Pro upgrade in Septic Sizing Plumb?
The optional Pro upgrade for $2.99 offers unlimited saved calculation history, PDF export of results, a dark theme, and an ad-free experience. These features are not required for basic calculator use.
Does Septic Sizing Plumb have ads?
The base version of Septic Sizing Plumb contains advertisements. An ad-free experience is available as part of the optional Pro upgrade.
What standards does Septic Sizing Plumb comply with?
Septic Sizing Plumb complies with the International Residential Code (IRC) Tables P2602.1 and P2602.2 for minimum septic tank size and absorption field area requirements, respectively. It also uses a standard residential design flow of 150 gal/bedroom/day.
Is Septic Sizing Plumb suitable for custom percolation tests?
Yes, Septic Sizing Plumb allows you to override the pre-set soil rates. You can enter your site-specific custom percolation test results for more accurate drain field area calculations.