DDW-2024-009551

195 North 1950 West • Salt Lake City, UT
Mailing Address: P.O. Box 144830 • Salt Lake City, UT 84114-4830
Telephone [phone] • Fax [phone] • T.D.D. [phone]
www.deq.utah.gov
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State of Utah

Department of
Environmental Quality

Kimberly D. Shelley
Executive Director

DIVISION OF DRINKING WATER
Tim Davis
Director

SPENCER J. COX
Governor

DEIDRE HENDERSON
Lieutenant Governor
POLICY MEMO

DATE: February 13, 2023

TO: All DDW Employees

FROM: Tim Davis, Director

SUBJECT: DDW Plan Review for Dichlor and Trichlor Installations Policy

EFFECTIVE DATE: February 13, 2023

ADOPTED DATE: February 13, 2023

Division of Drinking Water (Division, DDW) Plan Review for Dichlor and Trichlor
Installations Policy

I. Background
Current regulations regarding measurements of chlorine residual concentrations in drinking
water are based on measurements of free chlorine, or total chorine (i.e., free chlorine plus
chloramine chlorine species when chloramines are used). The DPD method, an EPA- approved
analytical method, measures chlorine residuals and can be used to distinguish between free
chlorine and total chlorine.

The Division reviewed the available literature and communicated with U.S. EPA regarding
analytical methods to measure free chlorine concentration in drinking water in the presence of
chlorocyanurate chlorine species (i.e., Dichlor and Trichlor dissolution products). The consensus
is that Dichlor and Trichlor interfere with the EPA-approved analytical method to measure free
chlorine residuals accurately. The interference likely results in erroneously high readings of free
chlorine concentration. Currently, there is no EPA-accepted alternative analytical method to
accurately measure free chlorine concentration in the presence of chlorocyanurates.

DDW Plan Review for Dichlor and Trichlor Installations Policy
Page 2 of 3

Utah Rule R309-520-4 stipulates that the effectiveness of primary disinfection is measured as
CT, a function of disinfectant residual concentration and contact time. The effectiveness of
secondary disinfection in distribution systems usually is measured in terms of C, disinfectant
residual concentration. Public health could be compromised if overestimated CT or C were used
in monitoring and reporting due to overestimation of free chlorine residual concentrations
because of chlorocyanurate presence.
II. Policy

1. Primary Disinfection – The Division will not approve the use of chlorocyanurates
as primary disinfectants if a water system is required to disinfect and meet the
disinfection CT requirements to comply with the surface water treatment or groundwater
disinfection regulations.
2. Secondary Disinfection – The Division will not approve the use of chlorocyanurates to
meet the secondary disinfection requirements if a water system is required to disinfect to
comply with the surface water treatment or groundwater disinfection regulations.
3. Elective Disinfection – The Division will not approve the use of chlorocyanurates if a
water system chooses to electively disinfect to comply with the surface water treatment or
groundwater disinfection regulations.
4. Treatment Other Than Disinfection – The Division may approve the use of ANSI/NSF
60-certified chlorocyanurates (e.g., Dichlor or Trichlor) if a water system proposes using
chlorocyanurates for maintenance of pipes/reservoirs/tanks or for treatment purposes
other than disinfection, unless it interferes with disinfection CT.
a) The approval will not include primary disinfection CT credit nor include
fulfillment of any secondary disinfectant residual (C) requirement.
b) Water systems not already monitoring and reporting regulated disinfection
by-products (DBPs), i.e., TTHMs and HAAs, in the distribution system will
be required to measure the concentrations of DBPs at the sampling
frequency and sampling sites specified per the DBPs regulations, and report
the results to the Division.
c) Water systems not already monitoring and reporting disinfectant residuals will be
required to comply with the monthly monitoring and reporting requirements
related to disinfectant residuals in the distribution system per the DBPs
regulations. The disinfectant residual measurement must be taken at the time of the
coliform sampling with sufficient additional residual samples to equal 3 residual
samples per week.

5. Existing Installation prior to implementation of this Policy – For a water system that
received approval from the Division and installed Dichlor or Trichlor facilities for
disinfection prior to implementation of this policy in August of 2016:
a. The Division will notify these water systems in writing of this policy,
specifically the following requirements in (b) and (c).
DDW Plan Review for Dichlor and Trichlor Installations Policy
Page 3 of 3

b. The water system is required to continue to monitor disinfectant
residuals and DBPs in the distribution system and report them to the
Division to comply with the surface water treatment or groundwater
disinfection regulations.
c. If the water system has a confirmed coliform positive sample when a
detectable disinfectant residual is present and the required RTCR
assessment finds no obvious cause of contamination:
• The use of chlorocyanurates will not be considered acceptable in
meeting the primary, secondary or elective disinfection requirements.
• The water system will be required to seek an alternative disinfection
method that can be verified by an EPA-approved analytical method.

6. In the Division’s SDWIS database, a facility indicator (CDCC) will be added to track
this type of treatment facility. The Division will develop a means of connecting the
water systems with the CDCC indicator to confirmed E. coli positive results in the
database. This tracking will trigger a SDWIS compliance schedule wherein DDW
follows through with the requirements for 4(c) above. The compliance schedule will
give a timeframe for the water system to seek alternative disinfection upon any
confirmed E. coli event. Failure to meet the acceptable time frame for installation of
alternative disinfection will result in a treatment technique violation.
7. This policy may be reevaluated if additional information becomes available, for
example, EPA-approved analytical method for measurement of fr ee chlorine
concentration in the presence of Dichlor or Trichlor, EPA policy or publication of CT
values specific to Dichlor or Trichlor.