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Disinfectant Residual Reporting in Drinking Water

Common regulated disinfectants for public water systems, monitoring and sampling, and using the DLQOR (disinfectant level quarterly operating report).

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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, chlorine or chloramines, in the distribution system. These PWS must use the Disinfectant Level Quarterly Operating Report (DLQOR) to submit a summary of the level of disinfectants, also called disinfectant residual, to TCEQ every quarter. 

Transient noncommunity systems do not have to submit the DLQOR, but 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 upon request. Find more information in Monitoring, Analyzing, and Reporting of Free Chlorine and Chloramines (RG-407). 

Minimum and Maximum Residual Disinfectant Levels

PWS in Texas are required to maintain a minimum level of disinfectant to kill microbes that can cause acute diarrhea, nausea, or other life-threatening illnesses. In addition, PWS must adhere to requirements for maximum residual disinfectant levels (MRDLs). Compliance for the MRDL is based on a running annual average of all samples collected in the distribution system. If that average exceeds the MRDL, a PWS must notify customers as soon as possible but no later than 30 days.

 Equation for Disinfectant Residual Running Annual Average

Table 1 Minimum Residual levels and MRDL by Disinfectant Type

Disinfectant Minimum Residual MRDL
Free Chlorine 0.2 mg/L 4.0 mg/L
Total Chlorine (Chloramines) 0.5 mg/L 4.0 mg/L

Sample Sites, Monitoring, and Sampling

All public water systems must monitor the performance of disinfection facilities to ensure appropriate disinfectant levels are maintained. Unlike sampling for chemical contaminants like minerals, metals, organics and inorganics, the PWS is responsible for collecting disinfectant residual samples. Monitoring must be conducted at sites throughout the distribution system and designated in your monitoring plan.

In addition, PWS that use chloramines must complete chloramine effectiveness sampling. 

Measuring the Disinfectant Residual

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

Disinfectant residual test kits can be found at: Hach, Fisher Scientific, LaMotte Company 

Questions about test kits must be directed to the manufacturer. 

DLQOR Form

The DLQOR Form (TCEQ-20067) must be submitted to TCEQ on a quarterly basis and can be submitted electronically through the Electronic Environmental Reporting (E2) using a State of Texas Environmental Electronic System (STEERS) account, or by mail. The mailing address is at the bottom of the DLQOR. Submit your data early to ensure it is received by the due date, 10 days after the end of the quarter. If you submit through E2, the program will tell you if required fields are missing and automatically calculates percentage of samples with a low residual, percentage of samples with zero residuals, and the quarterly average.

Table 2 Deadline to submit the DLQOR to TCEQ

Quarter First Second Third Fourth
Report data for January 1 to March 31 April 1 to June 30 July 1 to September 30 October 1 to December 31
Must be received by TCEQ April 10 July 10 October 10 January 10

If you have questions, contact DLQOR program staff at DBP@tceq.texas.gov or 512-239-1062.

Optional Disinfectant Residual Worksheets

Worksheets to record disinfectant residual results for your PWS. Do not submit these records to TCEQ unless requested.

Table 3 Worksheets to use based on sampling requirements

Fewer than 750 customers 750 to 4,900 customers Collects samples daily
PDF PDF PDF
Word Word Word

Customer Notification

Public Notice Language for Drinking Water Compliance - If your PWS has an MRDL, monitoring and reporting, or treatment technique violation, you can find required language and certificate of delivery documents by contaminant to use for public notification.

Consumer Confidence Reports - Community water systems must provide the minimum, maximum, and average levels of chlorine or chloramine in their annual Consumer Confidence Report to customers by July 1 of each year. A community water system supplies water to the same population year-round.

Assistance and Helpful Links

Temporary Free-Chlorine Conversion - Assists PWSs when making a temporary switch from chloramine to free chlorine.

TCEQ Drinking Water Viewer - Check the information TCEQ has for your PWS including chemical results, bacteriological results, sample schedules, violations, and contact information. This database is free and open to the public.

Technical Guidance for Public Water System Operators and Engineers - Find information about technical questions, such as submitting plans, exploring treatment options, or requesting exceptions to design or capacity rules.

Financial, Managerial, and Technical Assistance - TCEQ offers FREE financial, managerial, and technical (FMT) assistance to help PWS comply with regulations. Contact FMT for help with issues such as, but not limited to, preventing operational problems, training about how to comply with rule requirements and performing capacity assessments.