Septic systems installed in Hamilton County are regulated, permitted and inspected by the Health Department. Sizing of septic systems is based on the number of bedrooms and bedroom equivalents multiplied by 150 gallons per day per bedroom and divided by the soil-loading rate as specified in Indiana State Department of Health Rule 410 IAC 6-8.3. The soil-loading rate is determined during a site inspection performed by a Registered Soil Scientist. An update list of soil scientist and registered septic installers is available by contacting the Hamilton County Health Department.


Pressure distribution systems,Gravel-less systems, and Sand Line Systems may have different sizing requirements than provided in the requirement letter issued on a property.

Applications and Documents

The process by which an individual obtains a septic system permit is as follows:

Commercial Permits

Commercial Permits (PDF) - Procedures for any non-residential building served by on-site disposal