Indiana · small ground water systems
Indiana chlorine residual requirements
Short answer
IDEM's disinfectant residual form sets the figure Indiana systems report against: a monthly distribution average of at least 0.2 mg/L free chlorine (or 0.5 mg/L total chlorine) and no more than 4.0 mg/L. Residuals are measured with every coliform sample, and ground water systems that chlorinate file a monthly report of operation by the 10th.
- Minimum residual
- IDEM form: monthly average ≥0.2 mg/L free or ≥0.5 mg/L total
- How often
- With each coliform sample; daily at peak flow for 4-log systems
- Report
- Monthly Report of Operation (State Form 34609) by the 10th
Who has to chlorinate
- Ground water systems that must provide 4-log virus treatment follow the ground water rule; the residual limits in 327 IAC 8-2-8.6 apply to systems that filter. 327 IAC 8-2.3-5
Minimum residual
- IDEM's residual form: the monthly distribution average must be at least 0.2 mg/L free chlorine or 0.5 mg/L total chlorine, and no more than 4.0 mg/L. IDEM State Form 53296
Maximum
- 4.0 mg/L chlorine (as Cl2). 327 IAC 8-2.5-3
How often to test
- Community and non-transient systems: at the same points and times as total coliform samples. 327 IAC 8-2.5-3
- 4-log systems serving 3,300 or fewer: a daily grab sample during the hour of peak flow, every day water is served from the ground water source. 327 IAC 8-2.3-5
Test kits and methods
- With IDEM approval, free and combined chlorine may be measured with DPD colorimetric test kits. 327 IAC 8-2-8.7
Reporting
- Ground water systems that feed chemicals for disinfection are class WT2 and must submit monthly reports of operation within the first 10 days of the following month. 327 IAC 8-11-1
- The report is State Form 34609, with plant-tap and distribution columns for free and total chlorine. IDEM State Form 34609
- The disinfectant residual form (State Form 53296) is due within 10 days after the monitoring period. IDEM State Form 53296
How long to keep records
- Water systems keep their monthly reports for five years. 327 IAC 8-11-1
Keeping the log in Indiana
Because Indiana's monthly figure is an average, a few low days can hide inside an acceptable month. Keep the daily readings, not just the monthly number, so you can see a feed problem while it's happening.
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
- 327 IAC 8-2.3-5 — Ground water treatment and compliance monitoring
- IDEM State Form 53296 — Disinfectant residual report
- 327 IAC 8-2.5-3 — Maximum residual disinfectant levels
- 327 IAC 8-2-8.7 — Analytical methods for disinfectant residuals
- 327 IAC 8-11-1 — Monthly reports of operation
- IDEM State Form 34609 — Monthly Report of Operation, Water Treatment Plant
Last reviewed September 28, 2026. Rules change and states add their own; confirm with your state drinking water program.