AF Form 1689: Water Tank Calibration Guide & PDF Download

AF Form 1689: Water Tank Calibration Guide & PDF Download – AF Form 1689, officially titled Water Tank Calibration, is a critical Department of the Air Force form used to document the calibration of cathodic protection (CP) systems inside water storage tanks. This process ensures the integrity of tank interiors, prevents corrosion, and maintains the reliability of potable and non-potable water systems on Air Force installations across the United States.

Civil Engineer (CE) squadrons, particularly those responsible for infrastructure corrosion control and water systems, rely on this form as part of routine preventive maintenance. Proper use of AF Form 1689 helps comply with Air Force instructions, extends asset life, and supports mission readiness by safeguarding water storage infrastructure.

What Is AF Form 1689 and Its Purpose?

AF Form 1689 records measurements taken during water tank calibration surveys. These surveys verify that cathodic protection systems—whether impressed current (ICCP) or galvanic anode (GACP)—effectively protect the tank’s interior surfaces from corrosion.

Key purposes include:

  • Documenting potential measurements at specific locations (tank walls at surface, mid-depth, and bottom levels near and between anodes).
  • Recording anode-to-structure currents and rectifier performance (for ICCP systems).
  • Confirming that protective criteria are met and identifying any adjustments needed.
  • Providing a standardized, auditable record for annual performance reporting and compliance.

The form is referenced in corrosion control programs under DAFI 32-1001 (Operations Management) and older AFI 32-1054 guidance on cathodic protection systems. It supports broader infrastructure maintenance, including integration with forms like AF Form 1688 (Annual Cathodic Protection Performance Survey) and AF Form 1686/1687 for related systems.

Official Download: Access the current fillable PDF directly from Air Force e-Publishing:
https://static.e-publishing.af.mil/production/1/af_a4/form/af1689/af1689.pdf

Why Water Tank Calibration Matters for Air Force Installations?

Water storage tanks are vital assets for fire protection, potable water supply, and mission operations. Interior corrosion can lead to leaks, contamination risks, coating damage, and structural degradation—issues that are costly to remediate and can impact water quality compliance.

Cathodic protection calibration:

  • Measures structure-to-electrolyte potentials to ensure adequate protection (typically per criteria in Unified Facilities Criteria or UFC documents).
  • Uses reference electrodes placed at strategic points: near the water surface, mid-depth, and bottom, adjacent to anode strings and midway between them.
  • For tank bottoms, measurements are taken approximately 2 inches above the floor directly beneath anodes.
  • Includes rectifier operational checks, efficiency calculations, and current output verification for ICCP systems.

Calibration prevents excessive voltages that could damage coatings while confirming uniform protection across the tank interior.

When Is AF Form 1689 Required?

According to Air Force guidance (e.g., AFI 32-1054 and related UFC 3-570-06 updates):

  • Annually — as part of the scheduled preventive maintenance cycle.
  • 30 days after installation, modification, or adjustment of a cathodic protection system.
  • One year after the previous calibration (to re-baseline if needed).

These intervals ensure ongoing effectiveness, especially after system changes. Document all results on AF Form 1689.

Additional triggers may include post-maintenance reviews or as directed by the Base Civil Engineer (BCE) or corrosion control program manager.

How to Perform and Document Water Tank Calibration

  1. Preparation:
    • Review the tank’s cathodic protection design drawings and previous AF Form 1689 records.
    • Ensure safety protocols are followed (confined space entry if required, electrical safety near rectifiers).
    • Gather tools: reference electrodes, multimeter or CP-specific meter, clamp-on ammeter (for current measurements), and interruption equipment for ICCP surveys.
  2. Survey Procedure (simplified from UFC guidance):
    • For ICCP systems: Perform interrupted potential surveys (ON/OFF cycle with OFF typically 1 second; ON at least 4x longer). Measure potentials and rectifier output.
    • For GACP systems: Conduct non-interrupted surveys, accounting for measurement errors.
    • Take readings at required locations on walls and bottom.
    • Compare to previous data and protection criteria. Adjust system (current output, anodes, etc.) if criteria are not met.
  3. Filling Out AF Form 1689:
    • Complete header information: installation, tank identifier, date, personnel performing the calibration.
    • Record potential measurements, current values, rectifier data, and any remarks or corrective actions.
    • Include signatures and dates for accountability.
    • Retain the form in maintenance records or upload to approved systems (e.g., ACES, BUILDER, or government databases).

Always follow the latest version of the form and associated technical guidance. Training for CE personnel typically covers these procedures as part of corrosion control programs.

Integration with Broader Corrosion Control and Water System Management

AF Form 1689 fits into the Air Force’s comprehensive corrosion prevention and control (CPC) efforts. It complements:

  • Annual anode bed surveys (AF Form 1688).
  • Operating logs for sacrificial anode systems.
  • Leak/failure tracking (AF Form 1687).
  • Overall infrastructure management under DAFI 32-1001 and DAFMAN 32-1067 (Water and Fuel Systems).

Base Civil Engineers and utility system managers use these records to develop FYDP+3 infrastructure plans, prioritize repairs, and ensure compliance with environmental and safety standards.

Proper calibration reduces long-term costs by extending tank service life and minimizing unplanned outages or water quality issues.

Best Practices and Compliance Tips for U.S. Air Force Users

  • Maintain Records: Keep historical AF Form 1689 copies for trend analysis and audits.
  • Safety First: Adhere to confined space, electrical, and fall protection requirements when accessing tanks.
  • Coordinate with BE: Bioenvironmental Engineering may be involved for water quality aspects.
  • Use Official Sources: Always reference e-Publishing.af.mil for the latest form and instructions. Supplement with current UFC 3-570-06 (Operation and Maintenance: Cathodic Protection Systems) for detailed procedures.
  • Training: Ensure personnel are qualified in cathodic protection testing and Air Force-specific requirements.
  • Contractor Oversight: When using contractors, verify they document on AF Form 1689 and meet DAF standards.

For questions on implementation, consult your MAJCOM civil engineer or the installation BCE.

Download AF Form 1689 Today

Click here for the official fillable PDF:
https://static.e-publishing.af.mil/production/1/af_a4/form/af1689/af1689.pdf

Stay compliant and protect critical water infrastructure with accurate, timely water tank calibrations using AF Form 1689.

This article is for informational purposes and is based on publicly available Department of the Air Force publications and Unified Facilities Criteria as of 2026. Always verify the latest guidance on e-publishing.af.mil and consult your local CE authority for site-specific requirements.