Ohio · small ground water systems

Ohio chlorine residual requirements

Regulator: Ohio EPA, Division of Drinking and Ground Waters · Reviewed September 28, 2026

Short answer

Ohio requires community water systems to disinfect and to keep at least 0.2 mg/L free chlorine (or 1.0 mg/L combined chlorine) throughout the distribution system. Non-community systems that chlorinate must meet the same residuals. Residuals are checked every day at each entry point and at representative distribution points, and reported on a monthly operating report by the 10th.

Minimum residual: 0.2 mg/L free or 1.0 mg/L combined, throughout distribution
How often: Daily at each entry point and in distribution
Report: Monthly operating report (Form 5002) via eDWR by the 10th

Who has to chlorinate

All community public water systems must install and operate disinfection equipment that meets the rule. Ohio Adm. Code 3745-83-01
Non-community systems serving 1,000 or more people have the same residual requirement. Smaller non-community systems that chlorinate must maintain the same residuals. Ohio Adm. Code 3745-83-01

Minimum residual

At least 0.2 mg/L free chlorine, or 1.0 mg/L combined chlorine, at representative points throughout the distribution system. Ohio Adm. Code 3745-83-01

Maximum

4.0 mg/L total chlorine for community and non-transient non-community systems that use chlorine or chloramines. Ohio Adm. Code 3745-81-10

How often to test

At least once every day that water is available to the public, at each entry point and at a representative distribution point or points. Ohio Adm. Code 3745-83-01
A non-community ground water system that consists of a single building doesn't need the daily entry-point sample. Ohio Adm. Code 3745-83-01
Systems using chlorine only to oxidize iron, manganese or hydrogen sulfide are exempt from this monitoring. Ohio Adm. Code 3745-83-01

Test kits and methods

Ohio EPA recommends checking the calibration of DPD test kits at least once a year, reporting to one decimal place, and reporting the lowest result when several samples are taken in a day. Ohio EPA

Reporting

Systems prepare an operation report for each month, signed by the operator of record and submitted electronically by the 10th of the following month. Ohio Adm. Code 3745-83-01
Non-community systems that feed chlorine for disinfection monitor and report residuals on a monthly operating report. Ohio EPA

How long to keep records

Monthly operation reports: at least 10 years. Ohio Adm. Code 3745-83-01
Operator logbooks hold at least the previous three months of data at all times, and are kept at least 3 years. Ohio Adm. Code 3745-7-09

Parks, campgrounds and seasonal systems

Mobile home parks that are community systems must chlorinate. Campgrounds and other transient systems must chlorinate only at 1,000 or more people, but any that do chlorinate must meet the same residuals. Ohio Adm. Code 3745-83-01

Keeping the log in Ohio

Ohio's daily monitoring and three-year logbook rule make the daily log a required record in its own right, not just the source for the MOR. Keep the lowest reading of each day obvious, and write down calibration checks of your kit alongside the readings.

Print a dated month with the chlorine residual log sheet, or build a sheet for your whole round with the daily water system log sheet.

Other states

For federal rules and every state's program, see chlorine residual requirements.

Sources

Last reviewed September 28, 2026. Rules change and states add their own; confirm with your state drinking water program.