Keeping fire protection tanks in tip-top shape is crucial to maintaining a functional fire protection system. Fire protection is needed year-round without any interruptions in service. Tanks must have an adequate water supply and be properly maintained so that they are working during emergencies.
Tanks can be made of steel, wood, fiberglass or concrete. Steel is the material of choice for most fire protection tanks. It can be used to erect elevated tanks that are fed by gravity or for ground storage tanks. Both elevated and ground storage require similar maintenance, though elevated tanks are more expensive to upkeep.
They are also harder to heat, but they don’t require a pump system like ground storage tanks since they are pressured-based. Pump systems are necessary on ground storage tanks to boost water pressure.
The National Fire Protection Association recommends that tanks be cleaned and disinfected on a three-year cycle if they lack cathodic protection or on a five-year cycle if they have cathodic protection.
A mixture of dirt, sand, mud, and muck can settle at the bottom of tanks. Several inches or even a foot or more of mud and dirt can gather along a tank bottom. The sediment can then, in turn, clog up pipes and prevent the fire protection system from functioning properly. That’s why it’s important to clean out tanks at recommended intervals. Keeping the tank clean helps protect the owners’ assets and investments.
Cleaning can help prolong the life of the tank, and specifically the protective coating. Maintaining the tank regularly also keeps it running longer than it would if no repairs were made.
Remotely operated underwater vehicles controlled by qualified inspectors can clean most tanks without taking it out of service. Cameras attached to the ROV record video of the cleanouts. Trained divers can also clean out tanks without taking it out of service. The diver can also have a camera on their gear to record. Both ROVs and divers use trash pumps to suck the sediment out of the tank.
If a tank must be taken out of service during cleanouts, and it’s the only source of fire protection water storage for your facility, it is imperative that a reliable alternate or temporary tank be made available.
In regions with freezing temperatures, it’s extremely vital for fire protection tanks to have freeze protection. If a fire protection water tank isn’t properly heated to prevent ice from forming, it will jeopardize its serviceability. After all, it’s hard to put out a fire if the water has turned into ice cubes – especially if the ice becomes lodged in pumps, valves, the piping or the sprinkler system.
Tanks located in climates that produce freezing temperatures should be heated in accordance with the recommended practices of AWWA, M42, and NFPA. Following these basic guidelines should ensure the tank is ready to serve its intended purpose, but we ultimately hope the tank is never needed to respond to a fire.
Utilizing a combination of insulation and electric immersion heaters provides a very cost-effective method of keeping ambient water temperature above the 42° F. Fire protection tanks should always be heated and insulated. Electric immersion heaters alone are often not an economical option. They are big and require a lot of power, which can be costly. Small backup heaters are usually paired with insulation to keep expenses down.
Insulation is one way to prevent a ground storage tank from freezing. Elevated tanks are generally not insulated because the water typically circulates enough so that it is not normally susceptible to freezing.
Spray-applied urethane and panel are two types of insulation that tank owners can consider. The former is cheaper, but it has a few drawbacks. Overspray can be an issue, with the spray coating objects down below the tank like parked cars. One major drawback to spray-applied insulation is it is not susceptible to application in cold temperatures.
On the flip side, panel insulation, while more expensive, can be applied during the winter and there is no overspray issue. Once a tank is panel insulated, there is little to no maintenance required on the tank’s exterior. The interior will still need regular maintenance.
Cathodic protection can be added to a steel tank at any time. Older tanks are less likely to have cathodic protection. The prevailing belief, which still holds true for some people, was that a fine paint job and good workmanship make cathodic protection unnecessary. Unforeseen events, like bubbles in the paint, for example, can cause rust to form and eat through the steel. Cathodic protection provides another layer of protection.
An ultrasonic testing machine can scan tanks to determine steel thickness. Comparing the original tank drawings to the scans can help determine if the steel has experienced corrosion that results in metal loss or thickness has been reduced by corrosion that can lead to failure.
Updating Codes and Keeping Records
To keep in compliance with continuously changing standards and codes, fire protection tanks may need to be updated or modified from time to time.
Missing screens on vents and overflow pipes are examples of improper ventilation, which are some of the most commonly found code violations (Henderson). In a worst-case scenario, if a tank isn’t properly ventilated, pressure can build up over time and cause the tank to rupture.
Over the years, inspectors with Pittsburg Tank & Tower Group have found birds, squirrels, rats and other animals that have entered through an opening left due to a defective or missing screen. Secure screens keep out these critters.
Hatch covers on the roof should remain fastened to keep the tank secure. On welded steel tanks, a minimum two roof openings are required for personnel and ventilation during maintenance and rehabilitation activities (M42, p. 57).
Routine inspections can help identify problems that can then be addressed before they snowball into bigger issues. Records of inspections, maintenance, and any testing should be documented according to NFPA 25 standards. It’s beneficial to the owners and to anyone who performs inspections and maintenance on fire protection tanks to be able to refer to a written record.
Maintaining a tank requires time and attention, but the effort is well worth having functional fire protection. Don’t let something as basic as not securing a hatch cover or keeping adequate freeze protection cause your tank to malfunction when you really need it to work.
Erin Schmitt is the media director and technical writer for Pittsburg Tank & Tower Group, which was founded in 1919. Schmitt also has a bachelor’s degree in journalism from the University of Kentucky.