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System Sizing and Capacity Evaluation

System Sizing Requirements

Minimum sizing requirements for water sources, storage tanks, and water lines are specified in R309-510. Utah Code 19-4-14 supersedes some of the statewide requirements by directing the Division of Drinking Water to establish system-specific source and storage sizing requirements for public water systems. Until DDW sets system-specific sizing requirements for a water system, the statewide standards of R309-510 apply. The system-specific sizing requirements will be based on water use data that water systems are required to collect and report to the Division of Water Rights.

On June 28, 2023 an update to the DDW Detailed Guidance for Water Use Data Reporting and Setting System-Specific Source and Storage Minimum Sizing Requirements was approved. Here is a list of changes made to that document.

  1. The system-specific variability factor has been removed as a requirement for the calculations. A water system can still choose to use a variability factor if they desire to increase the minimum sizing standards. Language throughout the document was updated to reflect a water system could choose to use a variability factor. 
  2. Additional interpretation was added to section Division of Drinking Water’s Interpretation of Utah Code 19-4 Revisions incorporating the updates to 19-4-114 made during the 2023 legislative session.
  3. A new section, Division Policies to Aid in Finalizing System-Specific Sizing Standards, was added. This section describes methods to determine a safe yield for an existing water source that does not have one. Additionally, a section describes the methodology used by the division when a water system with a treatment plant has a raw water diversion before treatment. 
  4. Appendix A was updated to include the updates to 19-4-114 made during the 2023 legislative session.
  5. Changes for clarity of reading were made throughout the document, changing we to the Division and using consistent terminology for the system-specific variability factor. 

Information about water use data collection and reporting and system-specific sizing requirements can be found below:

The following report provides information about the collection of water use data needed to establish source sizing requirements and identifies metering equipment that may be capable of generating the required data:

If you have questions about the new water use data reporting and minimum sizing requirements,
please contact:

For questions about financial assistance that may be available for compliance with the new water use data collection and reporting requirements, please contact:

Public Water System Capacity Calculations

The following spreadsheets can be used to estimate the minimum capacity requirements for public drinking water systems. The protected spreadsheet is in a format that protects the formulas and links, while the unprotected file is available for individual modifications. These spreadsheets allow the user to enter the number of connections, irrigation and fire flow demands, existing source or storage volume capacities, etc.

  • Capacity Calculations Spreadsheet:
    Estimate the minimum capacity requirements for public drinking water systems

Public Drinking Water System Capacity Calculations—Examples

The following examples are capacity calculations for various water system types, including Community, Transient Non-Community (TNC), and Non-Transient Non-Community (NTNC) water systems.

Scenario 1—Fable Haven Town:

Scenario 2—Copycat Company:

Scenario 3—Papa Bubba Cafe:

Scenario 4—Spirited Away Campground:

Scenario 5—Fast and Furious Rest Stop:

Scenario 6—Sunrise RV Park:

Last Updated:


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