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Disinfectant Residual Reporting for Public Water Systems

Guidance and forms for public water systems to monitor and report disinfectant residuals collected in the distribution system.

All community and nontransient noncommunity public water systems (PWS) that use only purchased water or groundwater must regularly monitor and record the level of disinfectant in the distribution system and use the Disinfectant Level Quarterly Operating Report (DLQOR) to report this information to the TCEQ every quarter. Although transient non-community systems do not have to submit the DLQOR, they must monitor and record disinfectant residuals, complete the DLQOR and keep both records on file. These records and reports must be made available to TCEQ staff during routine inspections and upon request. Systems are required to keep records of disinfectant levels for at least three years. Find more information in Monitoring, Analyzing, and Reporting of Free Chlorine and Chloramines (RG-407).  

If your PWS treats surface water or groundwater under the direct influence of surface water (GUI), do not use the DLQOR form. You must submit the Surface Water Monthly Operating Report (SWMOR).

Disinfectant Residuals - Free and Total Chlorine

Systems are required to maintain a minimum level of disinfectant to kill microbes that can cause acute diarrhea, nausea, or other life-threatening illnesses. The minimum level of free chlorine required in the distribution system is 0.2 milligrams per liter (mg/L), if free chlorine is used. The minimum level of total chlorine (chloramines) required in the distribution is 0.5 mg/L, if chlorine and ammonia are added to the water to form monochloramine.

The maximum level of disinfectant was set by the Environmental Protection Agency (EPA) because of increased risks of cancer to people who drink water with very high levels of free or total chlorine for an extended period of time. The maximum residual disinfectant level (MRDL) is 4.0 mg/L, which is based on a running annual average of all samples in the distribution system. A single high sample will not necessarily put the system in violation, as long as the running annual average is below 4.0 mg/L.

How is the Disinfectant Residual Measured?

Disinfectant residuals within the distribution system must be measured to a minimum accuracy of plus of minus 0.1 mg/L using a colorimeter, spectrophotometer, or color comparator test kit. All test kits must conform to TCEQ and EPA analytical procedures. 

Where can Systems Find a Disinfectant Residual Test Kit?

If you have questions about test kits, contact the manufacturer. 


The DLQOR must be submitted electronically through the Electronic Environmental Reporting (E2) or a paper copy may be mailed to TCEQ. It's suggested that you submit your data early to ensure it is received by the due date. 

The DLQOR (TCEQ-20067) is available as a PDF file. This PDF file:

Reports are required to be submitted quarterly to TCEQ. If you have any questions, please contact DLQOR program staff at or (512) 239-4691.

  • Quarter 1 (data for January 1 to March 31) - DLQOR due April 10
  • Quarter 2 (data for April 1 to June 30) - DLQOR due July 10
  • Quarter 3 (data for July 1 to September 30) - DLQOR due October 10
  • Quarter 4 (data for October 1 to December 31) - DLQOR due January 10

Disinfectant Residual Worksheets

OPTIONAL worksheets are provided for you to keep track of individual disinfectant residual results for your PWS. These worksheets are not required; do not submit them to TCEQ.

  • for a PWS with 750 customers or fewer
    PDF · Word
  • for a PWS with 751 to 4,900 customers
    PDF · Word
  • for a PWS that collects samples daily
    PDF · Word

Public Notice Requirements

All public notices for DLQOR violations can be found at Public Notice Language for Drinking Water Compliance, under Other Drinking Water Rule Violations.

Assistance and Helpful Links

TCEQ's Drinking Water Watch holds the information we have for your public water system and is open to the public. This has contact information, sample sites, sample results, violations, and public notice due dates.

TCEQ's Financial, Managerial, and Technical (FMT) Assistance program offers free financial, managerial, and technical assistance to help public water and wastewater systems comply with regulations.

Temporary Free-Chlorine Conversion can assist PWSs make a temporary switch from chloramine to free chlorine.