The magnificent structure designed to protect and provide water for the people requires more attention than some water tank owners are aware is needed. Not only does a water tank demand routine inspections and regular cleanings but also routine maintenance.
A full bound report containing photographs and recommendations should be provided shortly after performing each yearly inspection and it is the tank owner’s responsibility to review the inspection report in a timely manner and address any maintenance issues found during the inspection. Emergency repairs and structural concerns should be addressed first, but all issues should be corrected to avoid more emergency repairs and fines in the future.
Emergency repairs can vary depending on the tank’s design and needs. A leak in the tank is obviously an emergency repair, but many may not realize a defective vent could also be an emergency repair. Improper ventilation and pressure buildup can actually cause a tank to rupture.
Therefore, vents, overflow pipes, drain valves and vortex plates should be carefully monitored for obstructions or defects that could lead to a blockage or pressure buildup. A defective vent could also allow birds to enter the tank, contaminating the water with feces and decomposing birds, insects or other animals. Several waterborne diseases could result from the contaminants, causing obstructions in the pipes and even clogging up the sprinkler heads hindering the effectiveness of the entire fire protection system.
It is important to remember the main purpose of a water tank is to protect and provide for the people, not endanger their lives or well-being.
In order to protect and provide for the people, it is mandatory a water tank maintain its structural integrity as the back bone of an entire water system. If the structural integrity is lost, then the distribution system could be considered a liability.
Each tank, depending on its design, has specific areas to be monitored more regularly than others for structural integrity. The foundation on all tanks is the obvious place to monitor for structural integrity, but there are other places as well.
For example, ground storage tanks without self-supporting roofs rely on the center column and roof rafters for structural stability. In some cases, the center column should not be completely welded to the floor because if the foundation settles and the floor sinks, it could pull the roof down with it. Instead, the center column should float with gussets added to the floor to prevent extreme movement of the center column, and the roof rafters should be welded to the center column to maintain the original designed strength.
With elevated water tanks, the riser pipe should be monitored closely for structural stability; if the elevated water tank has legs, then the legs, struts, windage rods and catwalk also contribute to the stability. To maintain that structural stability, the struts should be welded and the windage rods tightened regularly. The catwalk, which acts as a structural girder, should be securely attached to the shell of the tank. Standpipes and ground storage tanks with self-supporting roofs rely on the anchor chairs, bolts and shell for its structural stability.
The proper amount of anchor bolts and chairs should be spaced to meet design requirements. The shell thickness is another important issue for stability.
Most water tanks are made of steel, and if the thickness of the steel deteriorates to unsafe levels, the tank could spring leaks. Leaks are often the result of a cracked weld, which can occur from a frozen tank, pressure build up or excessive loading. Leaks can occur anywhere, but when a ground storage tank springs a leak in the floor it is usually the result of floor settling.
Most fire protection tank floors are lap welded on the top side only and sit on a ring-wall foundation with compacted sand placed in the middle. This compacted sand is a cushion to the tank floor, but over time the compacted sand can settle or wash out from under the tank.
When this occurs, a trained professional should pressure grout sand under the tank to maintain the cushion and stabilize the floor. If there is too much space between the compacted sand and the floor, the floor weld seams can crack. If the tank is an elevated tank, observing where the riser meets the bowl is recommended. The majority of the water weight settles in this area and often leaks appear at this connection. A saucer plate overlay can repair this, but it should be done by a reputable tank maintenance company that guarantees its work for at least ten years.
Pits can also create leaks if left unrepaired. Pits can appear anywhere in the tank and may need to be filled with a seam sealer or pit filler. Streamer pits are continuous pits that have formed in a vertical or horizontal line along the interior of a carbon steel storage tank.
These types of pits may need to be filled with weld or overlaid with steel plate. Some do not realize that maintaining the interior of a tank is more important than coating the exterior. The interior of a tank deteriorates faster than the exterior because it is in constant contact with water and chlorine, which causes the steel to erode faster. Maintaining the interior coating of a tank can prevent major renovations in the future.
Maintenance issues can also include insulation. Tanks for fire protection must be heated in areas that may produce freezing temperatures. They can be heated by steam, hot water, or immersion heaters. If a boiler system is already in place, heating the tank by steam may be desirable.
Hot water may also be used to heat a tank when an open circulating system is desired. For systems not already set up for steam or hot water, insulation and standby electric heaters can protect the tank from freezing. Insulation minimizes or eliminates the need for heating energy to provide freeze protection. Spray insulation and panel insulation are two forms that may be used to protect a water tank from the destructive outside elements.
When heating is required, energy costs can be reduced by as much as 90 percent by insulating the tank. Fire protection tanks are to be kept in perfect operation year round to be effectively used in case of an emergency situation. Fighting a fire with ice is difficult and impossible when ice must travel through pumps, valves, piping and sprinkler nozzles. Just one obstruction of ice in any of these fittings could result in a failed fire protection system. A false sense of security can be life threatening, and a fire protection tank containing ice is a greater liability than no tank.
Managing and maintaining a water storage tank can be costly, time consuming and a headache for most owners and operators. However, all of these issues can be avoided by enrolling each tank into a yearly maintenance program, often referred to as an extended warranty. With this type of program, the water tank will be inspected, cleaned and maintained regularly for a set fee. Having a professional tank company with the qualifications necessary to perform any and all issues that may occur with the tank is the way to insure the tank is given the attention required.
Erika Henderson is the director of research for Pittsburg Tank & Tower.