SepticTankLab The homeowner's field guide

Guide hub

Sizing & Installation

A septic tank is sized by bedroom count, not by how many people live in the house. The drain field is sized by the soil. Most sizing mistakes come from mixing those two up.

7 guides

Start with the septic tank size guide for the tables and how states differ. For a typical home, the 3-bedroom page gives the short answer, and how big a drain field needs to be covers the part that takes over the yard.

Before anything is installed, the lot has to pass a perc test, and the result decides which system it can take. Already own a system? See how deep tanks usually sit and how to find a buried tank, cheapest method first. If you are planning something small, read septic options for a tiny house, cabin or ADU.

Minimum sizes come from state and county codes, and they change. Check the current rule with your local health department before you design or buy.