Household Sewage Treatment Systems

Household sewage treatment systems are regulated under the authority of Chapter 3718 of the Ohio Revised Code and Chapter 3701-29 of the Ohio Administrative Code.

This program covers septic system siting, building lot approvals, septic system permitting, review of system operation and maintenance, and nuisance investigations. Regulations governing septic systems require soil evaluations on any new building lot, prior to existing system replacement, and at the time of minor subdivision parcel split-offs. Septic system types and sizes are determined by the type and condition of soil found on the individual properties.

Mercer County HSTS rules – effective May 1, 2021

Dwelling Replacement Policy – Board approved 8-12-20

For sewage system contractor information Click Here

For state forms: Sewage Treatment Forms

For general information regarding sewage treatment, visit the Ohio Department of Health Sewage Program home page:ODH Sewage Treatment Homepage
The Mercer County Minor Subdivision Rules / Planning Commission website: Mercer County Planning Commission website 

HSTS Frequently Asked Questions

Soil Evaluator List

2021 Installers

2021 Septage Hauler List

2021 Service Providers List