From The Editor | August 8, 2014

Water Quality Issues? It Might Be A Storage Tank Maintenance Problem


By Kevin Westerling

water tower

Throughout the treatment process, every drinking water utility works to avoid disinfection byproducts (DBPs), discoloration, and taste and odor issues. But often, those problems occur outside of the treatment scheme entirely.

Storage tanks are a prime setting for sediment buildup and bacterial growth, which can result in discolored and even potentially unsafe water.  Tanks can develop layers of cooler “heavier water” and warmer “lighter water,” which can create barriers in the water level that inhibit mixing. When water isn’t mixed properly, it can result in extended water age in the tank as “older” water continually stays in the tank, while the “newer” water is distributed out.

Tanks can also be the site of problematic chemical reactions. Reactions between disinfectants like chlorine and organic matter can occur inside the tank and cause acids that reduce the pH in the water and decrease the effectiveness of the chlorine. This results in DBPs and taste and odor issues.  Tanks can also present a major security risk if they are accessed by unauthorized individuals.

All of these issues can be avoided if storage tanks are properly maintained and monitored, explains Frank Houston of DN Tanks.  But many utilities are falling behind.  Houston shares his maintenance schedule recommendations that will keep any water storage tank, and as a result overall water quality, in tip-top shape. 

Tank Inspection On A Daily And Weekly Basis

  • Check to make sure all screens are intact and tight and inspect all vents and overflows.
  • Look for cracks or corrosion in the tank’s structure, coating failure, and wet or damp areas.
  • Make sure all ladders are safe and secure, and all hatches, locks, and hinges are functioning properly.
  • Identify any other potential issues before they become major problems.

Tank Inspection On A Monthly And Quarterly Basis

  • Perform a visual inspection of the tank’s interior and a limited visual inspection of its exterior.
  • Determine the cause of any recurring water quality problems.
  • Inspect corrosion areas, concrete, operating systems, exterior paint,  coatings, and sealants, and document acute changes.

Tank Inspection Every 3 to 5 Years

At this period, a complete inspection and evaluation of the tank interior and exterior should be performed. This should include an inspection of:

  • Sanitary conditions
  •  Structural conditions
  • Safety equipment conditions
  • Coating systems conditions
  •  Security conditions
  • Mechanical conditions
  •  General details
  • Interior tank deterioration

It is important that utilities don’t just inspect their tanks for issues, but take immediate action to fix those issues when they are found.  Tank rehabilitations, retrofits, and enhancements should not be put off or water quality will suffer, says Houston.  When a utility takes care of its tanks, it ensures that the water system is safe and reliable, and in compliance with all state and federal requirements.

Image credit: "Raleigh Watertower" Donald Lee Pardue © 2011, used under an Attribution 2.0 Generic license: