The Maguire Iron Podcast: 5: American Water Works Association
August 5, 2019
The Maguire Iron Podcast: 6: Water Systems Engineering
September 5, 2019
Water Tank Interior Inspection

The interior of a water storage tank is one of the most important parts of water distribution as the tank holds treated potable water for end-users within the system. Organic and inorganic residues can collect on surfaces inside water storage tanks and can lead to taste and odor issues, problems with regulatory compliance and can cause other complications within the distribution system.

Not all water tanks or water systems are the same and choosing the best type of interior water tank inspection can be difficult based on your systems unique needs and the amount of time the tank can be offline.

This article will explain the four different water storage tank inspection options along with the advantages and disadvantages of each. Water storage tank inspections should be conducted on a yearly basis. The goal of the inspection is to monitor the interior steel and coatings to minimize downtime and maximize water quality. All water tank inspections should be done in compliance with all American Water Works Association and Occupational Safety and Health Administration standards.

Water Tank Interior Inspection
A Maguire Iron N.A.C.E Level 3 Coatings Inspector climbs to the top of an elevated water storage tank to conduct an interior inspection.
The American Water Works Association recommends: “Tanks should be washed out and inspected at least once every 3 years, and where water supplies have sediment problems, annual washouts are recommended.”

(AWWA Manual M42, ch. 8, paragraph “Tank Washouts,” p.88)

When conducting a water tank interior inspection, one of the following four inspection types should be chosen based on your systems unique needs to determine the interior condition of the water storage tank to properly plan for long-term maintenance of the asset:

Interior Inspection Types

    1. Visual Inspection

    2. Remote Operated Vehicle Inspection

    3. Dive Inspection

    4. Washout Inspection

Visual Inspection

A visual inspection is the simplest form of inspection that can be performed on a water storage tank. This type of inspection is as easy as climbing or accessing the water storage tanks manway, opening it and recording what is seen. Capturing pictures of the roof, walls, and bottom of the tank are recommended to document the tanks structural material and the coating systems performance.

  • Advantages
    • Tank remains in service
    • Inexpensive

 

  • Disadvantages
    • Interior conditions cannot be fully inspected
    • Coating touchup cannot be performed
    • Sediment cannot be removed
    • Chemical cleaning cannot be done
    • Inorganic materials are difficult to detect

 

*Maguire Iron does not provide dive inspections

Water Tank Interior Inspection
A visual inspection photo of the bottom and walls of the tank taken from the roof manway of an elevated steel water storage tank while it the tank is still full of water and in service.
Water Tank Interior Inspection
A visual inspection photo of the roof structure taken from the roof manway of an elevated steel water storage tank while it the tank is still full of water and in service.

Remote Operated Vehicle Inspection

A remote operated vehicle inspection is performed when an unmanned submersible is placed in a water tank while it is full of water. The ROV is then flown in the water capturing pictures and video of the walls and bottom of the tank to document the tanks structural material and the coating systems performance.

  • Advantages
    • Tank remains full of water
    • Almost all areas can be inspected

 

  • Disadvantages
    • Some interior conditions (blistering) cannot be fully inspected due to water in the tank
    • Coating touchup cannot be performed
    • Sediment cannot be removed
    • Chemical cleaning cannot be done
    • Inorganic materials are difficult to detect

Dive Inspection

A dive inspection is performed when a diver dives in a water storage tank while it is full of water. The diver captures pictures of the roof, walls and bottom of the tank to document the tanks structural material and the coating systems performance.

  • Advantages
    • Tank remains full of water
    • Almost all areas can be inspected
    • Sediment can be removed

 

  • Disadvantages
    • Some interior conditions (blistering) cannot be fully inspected due to water in the tank
    • Coating touchup cannot be performed
    • Chemical cleaning cannot be done
    • Inorganic materials are difficult to detect
Water Tank Interior Inspection
A diver preparing to conduct an underwater inspection.

Washout Inspection

A washout inspection is performed when a water storage tank is drained and an individual or crew enters the tank to conduct the inspection. The individual or crew captures pictures of the roof, walls, bottom and all other structures inside of the tank to document the tanks structural material and the coating systems performance.

The crew can then power wash all surfaces of the interior of the tank to remove any sediment and organic materials.

  • Advantages
    • Most complete condition assessment can be accomplished
    • Sediments can be removed
    • Full preventative coatings maintenance can be accomplished at the same time
    • Coating touchup can be performed
    • Chemical cleaning can be done
    • Inorganic materials can be detected

 

  • Disadvantages
    • Tank must be drained and taken out of service
Water Tank Interior Inspection
Sediment left over after tank is drained. This sediment will be removed prior to tank being filled.

In Summary

Safe potable water delivery is the number one purpose of a water storage tank. Proper interior inspections will help you document and determine the condition of your water storage tank to help you properly plan for long-term maintenance. Inspections on the water tank need to be done every year for maintaining the sanitary, safety, structural and coatings. So setting a schedule and then determining when and what type of inspection you require and in what years helps monitor the tank condition.

At Maguire Iron, we provide a full range of interior inspection services including:

  • Visual Inspections
  • Remote Operated Vehicle Inspections
  • Washout Inspections

We also offer maintenance plans tailored to your water tanks specific needs and budget. Call us today at 605-334-9749 to schedule an appointment with one of our water tower experts to determine your tanks interior condition and the best way to manage one of your most important pieces of infrastructure.