Old and new methods

Tank inspections can be accomplished by one of three methods: draining, dropping in a Remotely Operated Vehicle (ROV), or sending in a diver.

Draining

The oldest method of inspecting water reservoirs is to drain them. The reservoir is taken off-line and emptied, wasting valuable water and disinfectant. Workers then enter the reservoir to clean the floor and perform maintenance by hand. For steel tanks, draining can lead to damage of the interior coating. Walking around the inside of an empty reservoir can cut small scratches in the floor coating, causing the underlying metal to rust after the reservoir is refilled. Workers walking inside a tank generate a substantial risk of contamination and are subject to confined space regulations. Concrete reservoirs often suffer structural damage from the expansion and contraction that occurs from moving large quantities of water. This method requires extended down time, and is the most expensive.

ROV inspection

Remotely operated vehicles (ROV) are useful for assessing the condition of a reservoir's interior without contamination, downtime, or confined space concerns. However, ROVs cannot effectively clean, remove debris, or perform repairs.

Commercial Hard Hat Divers

"A competent commercial diver, experienced in water tank design and rehabilitation, may perform the inspection without draining the tank..."

Commercial divers that use the proper equipment are the best choice for overall tank maintenance. Divers perform the work while the tank remains in service and full of water, eliminating the high cost and dangers associated with normal tank maintenance. A diver can do what ROVs cannot, like repairing cracks or coating failure, cleaning the reservoir, or replacing corroded fixtures.