The need for water tanks with a long service life in a time of aging infrastructure has become an increasingly critical issue. Additionally, that issue is being compounded by continued development and drought. And whether a conveyance provider is constructing a new tank or replacing an old one, there are many choices to fit the need.
The Problem of Aging Infrastructure
Bill Neighbors, president of Tank Connection, says that water storage issues are being compounded by North America’s aging water infrastructure, “which is out of control and money is not being spent on it. We have a long list of issues that are colliding with water. Not only that, but water is not going to be cheap in the future. There is not going to be technology that keeps it cheap. We’re running out of it. We’re overexploiting it.”
While those issues may present a lot of business opportunities for those manufacturing tanks and pumps, “it also says a lot about what isn’t being done today to prevent an infrastructure in the future that isn’t all of a sudden going to need trillions of dollars pumped into it–right now, it’s tens of billions,” he points out.
In addition to what he calls an “overexploited water supply”, Neighbors says factors such as climate change are “colliding to make water one of the most important priorities going forward.”
Neighbors says while water storage products of varying qualities can be purchased and installed for about the same price, the life-cycle costs add to the equation. The average service life of a storage tank use to be considered 40 years, says Neighbors.
“In today’s storage industry, there are tank/containment products being introduced into the market that will provide less than a 10- to 20-year service life, and other products that will provide service in excess of 60 to 80 years.”
“It becomes an expensive lesson for the client when marginal and poor quality tank construction is specified and procured for a project,” he says. “The construction of a storage tank system should always be reviewed as a major infrastructure project. Never assume a vendor will provide you with the right type of storage tank construction for an application.
“Always cover the specifications on tank construction, coating systems, and field construction processes in detail. Then you can specify and procure a premier quality storage system with confidence.”
Steel for Large Capacity
A steel tank is the most economical tank to purchase for aboveground storage, says Neighbors. Tank Connection designs, fabricates, and installs four types of steel storage tanks, including bolted RTP (rolled tapered panel), field-weld, shop-weld, and hybrid tank construction.
“In a small capacity, the most economical product is the shop-welded tank,” he says. “When you get into large capacities for municipal water storage, you’re going to either be looking at a bolted steel tank–ours is a rolled tapered panel–a bolted flange panel tank, which is an older technology; or a bolted flat panel tank, which doesn’t have a taper.
Tank Connection ships water tanks worldwide. Neighbors notes that there are different international standards and products are being manufactured that are cheaper and lighter.
“We counter that,” he says. “A good counter to that is a code to keep everyone on the same page, which are tanks built by ANSI/AWWA D103 for bolted and ANSI/AWWA D100 for welded. Anything else is really unacceptable in the marketplace.”
CB&I manufactures ground level welded steel reservoirs and standpipes in nearly any capacity and dimension to meet design, economic, or aesthetic needs. The company introduced welded steel tanks in the 1930s. The company has built the tanks from one million gallons or less to as large as 34 million gallons. Reservoirs have a greater diameter than height. They offer economical and effective storage, especially when located on high ground. They can take on a lower profile by being hidden by foliage.
The primary advantage to welded steel tanks is zero leakage tolerance as required by AWWA D100, says Rich Horn, regional sales manager for CB&I. With proper maintenance and operation, steel tanks can exceed 100 years of service, he says, while also pointing out that they are often favored in high seismic zones or high wind load applications.
American Structures designs and manufactures stainless steel bolted storage tanks.
“Stainless steel has a residual value,” points out Rosemarie Bristol, marketing and sales manager for American Structures. “It can be torn down and relocated. It’s food-safe. They are expandable. We can make them smaller or larger as the needs of our customers dictate. We can make some large in diameter and shorter, and we can make them like stand pipes where they’re taller and have a more minimal diameter.”
Bristol says while stainless steel has a reputation of being more expensive, its built-in residual value offers more worth in the long run. One of steel’s main benefits is that it doesn’t have to be painted, says Bristol.
“It’s environmentally friendly and blends in nicely with the environment,” she adds. “It generally doesn’t have to have maintenance–it doesn’t have to be cleaned or scraped out. It has a long life expectancy.”
Steel tanks have “residual value.”
There are overlapping panels in the tanks with epoxy applied at the bolt-holes. The adhesive–as well as the bolting compression–keeps them watertight, says Bristol.
“They weather variances in temperature very well,” she adds. “It’s not like you have a lot of expanding and contraction where come spring you’re going to have leaks.”
Standards and Regulations
Steel tanks do require maintenance, Horn says.
“We recommend they have an inspection of their tank every three to five years,” he says. “If they do that and touch up areas of paint they’re constantly having problems with, they can extend that particular paint coating even longer. With some of these new high-tech coatings, I don’t envision some of them having to be repainted for 25-plus years.”
Additionally, in that 25 years, all that’s required is to brush-blast the coatings and apply a topcoat rather than a “full blast down to bare metal”, says Horn.
It’s a “myth” that some tanks are maintenance-free, declares Horn, adding that all tanks require maintenance to achieve their design life. It’s also a “myth” that steel tanks must be blasted down to bare metal every eight to 10 years, he adds.
“Industry research and testing data actually show complete renovation intervals of 20 to 30 years,” says Horn.
Some states like California have special requirements for tanks, including those of concrete construction. California regulations require tanks to be of impervious construction to prevent the movement of water into or out of the tank.
AWWA standards for concrete tanks–AWWA D110-04 for wrapped pre-stressed and D115-06 for tendon prestressed–have an allowable leakage rate for the tank as constructed. Tank construction must be specified in excess of AWWA standards to achieve a tank in compliance with the regulations, says Horn.
California regulations also require that all potable water contact materials–materials of construction such as concrete or coatings, linings, gaskets, and sealants–must be certified in accordance with ANSI/NSF Standard 61. Although the California Code of Regulations requires the water system operator to only use materials and products certified for compliance with NSF Standard 61, the AWWA standards for concrete tanks do not require the use of NSF 61 certified products.
Therefore, for construction of new tanks, the tank owner must specify that compliance with NSF Standard 61 is required in order to ensure that the tank will comply with California code requirements, Horn says. A benefit of an aboveground storage elevated tank is in the water-energy nexus, Horn points out.
Storage As an Energy Saver
“Municipalities save a lot of money because, with their peak water period or demand period that they are going to pump with using an underground storage tank, there also is a peak demand for electricity,” explains Horn.
Utility companies can make more money during that time period as they maximize their equipment and thus charge more per kilowatt-hour to pump through that peak time demand of water as well as electricity, Horn adds.
“On elevated tanks, or even with a ground storage tank, you’re able to put on the side of a hill on gravity flow, if you pump the water up at night when the rates are less expensive per kilowatt-hour, you can save a lot of money during that demand period by gravity flowing,” he says. “One of the main advantages of having aboveground versus belowground is saving that peak demand cost.”
Aesthetics and Function
One of CB&I’s many water tank structures that dot the US landscape can be found in Darien, IL. There, the company built a standpipe water tank that resembles a lighthouse, with 3-D windows and a spiral staircase going up the pilasters.
“It’s got some very nice aesthetics,” says Horn. “Having that above ground adds to community pride.”
The Steel Tank Institute/Steel Place Fabricators named the 1.5-million gallon standpipe water tank “Tank of the Year” in 2007. The water tower is actually a response to the need for adequate water supply and storage for Darien, says Daniel Gombac, director of Municipal Services.
One challenge: the tower was to be located near a residential and retail area.
“The old tower that was up was a water tower that had served its time and did not function very well from an aesthetic standpoint, as well as a mechanical standpoint,” notes Gombac.
Gombac says instead of putting up a “Thermos” bottle with a “nice” color on it, he conceived something more attractive and talked to engineers about incorporating windows with trim on the outside.
“During my preliminary conversations with our engineer, he basically looked at me and said, “˜You’ve got to be kidding me.’ The windows were to be orientated in a finishing where it appeared you’d be walking up a spiral staircase–a window spiral staircase either on the tank or inside the tank to create that illusion of it.”
After several renderings and CB&I agreeing to meet the design challenge, the design started to take shape. Another creative touch addressed the issue of cell phone companies using water towers for their equipment.
“One of the things you always see on water towers is all of these wires,” notes Gombac. “We decided to use the pilasters for the tank as a cable shield, and around the perimeter of the top of the tank we created another illusion as well to hide all of the wire and antennas–mounting them in a low-profile way off of the catwalks and handrails. You can’t even tell it’s being utilized as a cell site of any sort.”
The “lighthouse” water tower
blends in with the environment, Gombac points out.
“The colors blend in with everything around with the retailers and for the residential area, there’s a tank in the “˜backyard’ that at least has some character and style, versus “˜here’s a piece of steel up in the air’,” he says.
His one issue of concern for the future is repainting it. “We anticipate it should last up to about 15 years,” he says of the original paint job.
Gombac says welded steel allowed the city maximum storage with structural stability. The storage encompasses projected future development.
“The tank was a challenge to everyone involved, from the engineers to the guys building it,” says Gombac. “I think it was a well-thought-out project, and by winning tank of the year, that’s an accolade in itself.”
When Concrete Is Called For
Concrete tanks require the least maintenance of all choices, says Eric McGee, regional manager of business development for DN Tanks.
“Because they’re low maintenance, they’re popular as clear wells, which means they can be continuously operated without any downtime to recoat,” he says, adding that because of that factor, concrete tanks can be placed at remote sites.
Concrete tanks are durable, McGee points out.
“Concrete tanks are bulletproof,” he says. “Most tanks are pretty remote out in the middle of nowhere, and people like to take shots at them.”
The seismic reliability of the concrete tanks–especially the prestressed tanks with anchored flexible connections–is greatly enhanced, McGee says. The tanks can be painted any color, with anti-graffiti coatings applied. Any graffiti that does make it onto a tank can be removed with a solution, he adds.
One of the challenges of concrete tanks is they have a higher upfront capital cost over steel. Also, because the tanks are aboveground, they do have a visual impact, and as such, “if you want to site one in a neighborhood, there are groups that are against that,” points out McGee.
Constructing them on a steep mountaintop can be a challenge in getting the concrete trucks up steep slopes.
“A lot of sites are pushed into the hillside or on top of a hill,” says McGee. “There are challenges with a real small footprint.”
Stephen Cesar of SBC Consulting Engineers–a municipal and rural water engineering firm in Altus, OK–says his firm is engaged mostly in upgrading and maintenance issues and once a year may be involved with a new tank construction. For ground storage tanks, he favors prestressed reinforced concrete, although he points out that the tanks can have cracking and leaking problems.
Cesar favors steel for elevated tanks. His company will design for standpipes up to 150 feet, and beyond that, “you’re going to have to go to a real elevated tank,” he says.
Maintenance after installation requires a visual inspection from the outside and, following the American Water Works Association guidelines, sending a diver or floating a boat inside the tank and doing a visual inspection from the inside once every five years, McGee says.
The tank also can be vacuum serviced. Generally, a prestressed concrete tank is crack-free, McGee says.
“There usually shouldn’t be any repairs,” he says. “If a crack shows up, it’s generally epoxy-injected or cap-sealed.”
When Fiberglass is What You Need
While the bulk of its tank storage market is in underground tanks and is primarily for the petroleum industry, fiberglass tank manufacturer Xerxes finds
Aboveground storage offers flexibility and adaptability.
itself doing a significant volume in water applications as well, notes Tom Tietjen, vice president of sales and marketing.
“Water, unlike some of the petroleum products, is perfectly suited for aboveground or underground use,” he says.
Typical aboveground applications include rainwater harvesting, potable water, and fire protection tanks. While his company does not advocate for one type of tank over another and instead responds to the needs of a designer, engineer, or end user, there are some drawbacks to underground storage that should be taken into account, Tietjen says.
“If it’s going to be outdoors, which oftentimes these tanks are, it’s the climate,” he says. “If you’re storing water above ground outdoors for whatever purpose, you have to protect that vessel from freezing.
“There are certain applications or a desired temperature range that the water needs to be maintained at, but folks don’t want their water freezing in an aboveground application, so they either have to insulate it or heat it–do something to prevent freezing.”
If the choice is to put the tank in an indoor setting, there’s an expense associated with that, Tietjen says, adding that there’s a footprint issue in the amount of square footage inside of a building being dedicated to storage.
Tanks are installed above ground in either a horizontal or vertical configuration.
“If you’re going to go horizontal on saddles, it takes up an even greater footprint inside a building,” says Tietjen. “Another downside to aboveground is the aesthetics. This is site-specific. If you are a manufacturing facility out in the suburbs somewhere and you have enough property, the appearance of a series of storage tanks may not be a consideration. If you’re in an urban environment, it’s certainly a consideration.”
That also is the case with the increasingly popular application of rainwater collection.
“For the kinds of buildings collecting rainwater, aesthetics or visibility of storage tanks is an issue,” says Tietjen. “It might be a school or an office building–those are kinds of facilities typically where owners don’t want visible storage tanks.”
Repair should not be a concern for fiberglass tanks, Tietjen says. If the tank is specified and designed properly in the first place, a fiberglass tank is non-corrosive, he adds.
“It’s immune to rust and corrosion for water storage and if it’s designed correctly and is constructed with the right surface coating, it shouldn’t have UV damage or require painting or coating in the future,” says Tietjen.
Still, most of the company’s end users opt for underground storage.
“In talking with design engineers, civil engineers, and folks who are involved in project work for water storage, we frequently find as we talk about the options of underground or aboveground storage, that they hadn’t really considered underground,” says Tietjen.
“The tendency is to think about aboveground storage for water, and when we mention the underground option, it’s a “˜out-of-sight, out-of-mind’ issue for a lot of folks,” he adds. “They don’t think about large capacity tanks being underground. When you talk about that option, it’s sort of a revelation that maybe that makes sense.”
Containment Solutions (CSI) manufactures a variety of fiberglass water storage products, including aboveground applications.
For residential markets, CSI manufactures the Water Geek line of tanks ranging from 300 to 1,050 gallons. Each tank is 6 feet in height to stay within fence line restrictions.
“This is an excellent entry level tank for homeowners interested in rain harvesting,” says David Heiman, CSI’s marketing director.
Installation ease is the primary benefit of aboveground storage water storage tanks, Heiman points out.
“A fiberglass aboveground tank is easy to ship and easy to install,” he says. “Fiberglass tanks arrive to the job site fully assembled–you simply offload and connect piping. Underground installations are typically preferred for large volume tanks–especially where usable real estate is limited or expensive–but in rural or mountainous areas, aboveground tanks can be a perfect solution.”
While aboveground tanks are more accessible than a buried tank, one of the biggest challenges is exposure, says Heiman.
“Sunlight, wind, and water can be detrimental to an aboveground system,” he says. “Years of exposure to the elements cause rust, degradation, and leaks. Choosing the right tank manufacturer is just as important as choosing the right system design. Fiberglass is non-corrosive so unlike steel tanks a fiberglass tank will not rust even after decades of use.”
Space can be a challenge for aboveground tanks, he points out.
“In many areas, property is either too expensive or too scarce to justify a large diameter aboveground tank,” he says. “Often underground tanks, despite the higher installation expense, are preferred so the land above is still usable for open structures such as parking lots or green belts. Aboveground tanks might not be the best solution for everyone.”
Aesthetics and tank visibility impact aboveground storage decisions.
Some maintenance can be expected on any system, especially when PVC piping is used in areas that can freeze, Heiman points out.
“Some tank options have inherently more expected maintenance than others,” he says, adding that, in contrast to other tank materials, fiberglass tanks neither rust nor depend on a bladder with a finite shelf life.
“Fiberglass tanks will remain in service for decades, with virtually no direct maintenance or repairs,” he adds. “In the case of repairs or modifications, fiberglass is a product that can be permanently altered after being installed.”
Other Options
Composite tank, a new field for American Structures, is viable option when installation or other needs are trickier than typical water storage scenarios.
“Most people who have wanted composite tanks for water towers wanted the welded tanks, and we do minimal field welding on our tanks,” says Bristol. “There would be nothing stopping someone from putting bolted stainless steel on top a concrete pier and make it an elevated tank.”
Snyder Industries offers a variety of water storage tanks molded out of polyethylene with capacities of up to 15,000 gallons.
“It’s a less expensive alternative to other materials,” says Dave Kelley, director of sales and marketing for the septic and water tank division of Snyder Industries. “It’s not a corrosive, and, with the variety of uses of the tank, it also can be NSF-approved and is FDA-compliant.”
The tanks also are lightweight and UV-resistant and are not susceptible to degradation under sunlight.
“They’re corrosion-resistant and can be easily cleaned,” says Kelley. “It can be made either translucent so you can see the water level inside, or we can make them opaque to block out UV to inhibit the growth of algae inside the tank.”
The tanks can be outfitted for a variety of packages for standard or engineered applications. Kelley says the tanks are widely used on the West Coast where there are a lot of fire protection codes.
Shipping can be a challenge, says Kelley.
“It’s not a product that’s assembled onsite, and you’re shipping a lot of air,” he says. “It’s not a heavy product, but it’s a bulky product.”
Kelley is starting to hear more talk with respect to water storage as it relates to drought and future growth. Snyder Industries’ tanks are often used for rainwater collection, with rainwater being used instead of drinking water for irrigation.
“There are certain areas of the country where we see more activity for tanks used for that purpose and it’s usually areas of the country that have experienced a severe drought or periodically dry climates, like the desert Southwest,” he says. “We’ve seen other areas like North Carolina and Georgia that have experienced severe drought.”
With municipal water “still an inexpensive source of water in most parts of the United States, that probably holds it back from a product that’s actually going to have a return on investment for someone,” says Kelley.
While many seek to make water tanks aesthetically pleasing, one recent application of a Snyder Industry tank focused only on that aspect.
The company constructed a bank of six 10,500-gallon aboveground water storage tanks that collect rainwater at the Bemis Center for Contemporary Arts in Omaha, NE. The water is then sprayed from jet nozzles mounted on the roof and during certain times of the day on sunny days, it creates a rainbow over the building–a living piece of art.