9 minute read
Protecting Your Tanks
By Erin Schmitt, Technical Writer/Media Director for Pittsburg Tank & Tower Group, originally run as separate articles.
Windage Rods Provide Stability
With so many components on an elevated legged tank, it can be easy to overlook windage rods. These are rods that provide bracing and stability to a water tower. They are not nearly as large or eye-catching as the tank shell – the part where a city’s logo is often emblazoned. They are also not the sturdy legs that are fixed in concrete and easy to see.
A fresh coat of paint helps prevent corrosion, which weakens steel’s integrity. Rusted windage rods are more likely to bend or break.
Windage rods should appear taut and without any sag or sway. If a windage rod is curved too much, that’s a telltale sign that it is too slack. If an inspector can grab a windage rod from the ground and it then wiggles or shakes – it’s too loose and needs to be tightened.
Windage rods can be judged on three points of observation:
1. Visual Inspection
A visual inspection can be performed to determine if windage rods are showing any signs of sagging, bowing, or movement that would indicate the rods are loose.
2. Touch and Feel
You can shake, knock or push on the rods to observe how much sway they have, and thus judge the rods’ tightness.
If the rod moves easily, it means the rods are loose and need adjustment.
3. Sound
Inspectors use a tool to knock on the windage rods and listen to their reverberations. Similar to a guitar string, the looser the windage rods, the deeper and longer the sound will reverberate. The tighter the windage rods, the higher and shorter the sound will be. When a tank is being professionally inspected, it’s best to use all three points of observation because one or two points might not provide the whole picture. Also, each method builds on the previous inspection check. However, if a rod passes the visual test, there’s typically no need to move on to the next observation point.
Visual inspections can be conducted from the ground or off the tower access ladder. However, if a rod appears loose, then a closer inspection is needed.
There’s no set timetable for when windage rods should be adjusted. There are several factors to consider. Did a strong windstorm, tornado, or hurricane recently hit the water tower? High winds can damage windage rods and other components, so the tank should be inspected immediately. If a severe storm struck the water tower, it’s very likely the windage rods need to be adjusted.
Saltwater is highly corrosive to metal. Storage tanks located along coastal areas typically begin showing rust much quicker than their landlocked counterparts. Elevated tanks along coastal areas will also likely need their windage rods inspected and recoated more regularly.
Otherwise, it’s not uncommon to see the need arise after a few inspection cycles – which is typically three to five years – depending on whether the tank has cathodic protection or not.
An elevated tank is designed to handle most natural disasters. Engineers factor strong wind speeds into the design and make it so the structures can withstand most high winds.
Of course, there are exceptions. An EF4 tornado with winds just shy of 200 mph (which would have made it EF5) barreled into an elevated legged tank in Mayfield, KY, and reduced it to rubble in December 2021. The tank was built in the early 1950s but had undergone significant maintenance work in the past five years. That still wasn’t strong enough to withstand a historic tornado.
But there have also been elevated tanks that have withstood direct hits from hurricanes with little to no damage. Regardless of whether you can see damage or not, it’s always best to have your tank professionally inspected after a natural disaster. After all, smaller elements or ones lofted higher in the air like a windage rod are easy to overlook.
professional inspections, tank owners should make a point to visually inspect their storage tank weekly. That could be as simple as taking a few minutes to walk around the tank and make sure there are no breaks in screens or holes.
Be mindful of other openings too. Cathodic protection holes should be fitted with covers to block access. If a tank’s rusted through, it’s susceptible to holes. Aside from being at greater
Keeping the Birds and the Bees Out of Storage Tanks
Birds and insects have a knack for finding a way into places they shouldn’t be. Birds, insects, snakes, and some animals can squeeze themselves into the smallest openings. Openings in and around water towers and tanks should be sealed off to prevent unwanted critters from entering.
The American Water Works Association recommends that tanks be inspected every three years. In between
risk for structure failure, a holy tank is open to contaminants and animals.
Ideally, a tank should have properly designed and fitted screens or patches covering any potential openings. Improperly designed or installed roof hatches and vents are entry points for birds and bees.
If a screen is improperly fitted, it can be difficult to get off. That may cause inspection or repair delays and could even result in remobilization costs if work is supposed to be done but cannot be performed because the contractors can’t access the tank.
Overflow pipes should be covered with a coarse, corrosionresistant screen and a flap valve, according to AWWA D100-11. Vents should be designed to prevent birds, insects, and animals from entering a tank, according to AWWA D100-11. The codes recommend installing a pressure-vacuum screened vent or a separate pressure-vacuum relief mechanism that works if the screen frosts over or clogs. Similarly, NFPA also calls for screens on vents and overflows to prevent animals from gaining entry.
Stub overflows are more likely to be infiltrated by critters because it’s easier to access. Extending an overflow down to grade and adding a flapper valve and screen helps prevent unwanted intrusions.
Hornets, wasps, and bees are drawn to cool and dry places like overflow pipes or inside the concrete shaft of a composite tank. Enter an area where hornets and wasps like to nest at your own risk.
Don’t kick the hornet’s nest is an idiom that means, don’t start trouble in a hazardous situation. If you literally kick a hornet’s nest, you might expect angry hornets to fly out at you, ready to sting.
However, sometimes you need to kick the hornet’s nest. That’s what inspectors do when they hit an overflow pipe to see if wasps or hornets have taken residence. It’s more like knocking to gauge the threat level. If there are hornets or wasps, the inspectors might not be able to finish their inspection until the pests are removed.
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Snakes can also crawl up pipes, though they are more likely to be found in valve pits. During a routine inspection in rural New York, an inspector came across hundreds of snakes at the bottom of a dark valve pit. He was unaware that the snakes were present until halfway down the ladder. By then, a few of the snakes were already slithering toward him. The inspection was not completed that day.
Birds like to make nests up high – away from predators. Water towers are naturally an attractive home for birds. If there are birds around a water source, there’s a greater chance that bird droppings or feathers, or even the whole bird might find itself inside the tank. To deter birds from nesting, tank owners might try putting up stuffed vultures, stuffed owls, or tube men – the flappy inflatables most often spotted at car dealerships.
It would be ill-advised to shoot birds because any pellets or bullets that miss could puncture the water tank or surrounding structures. Besides, many birds are protected by federal laws, so they can’t be harmed.
During one inspection, dozens of large turkey vultures circled an old tinman-style tank on a college campus. A college maintenance official knew just the trick to make the birds scatter – use a fishing pole to float a black helium balloon toward the birds.
Code Updates
In-Service Cleaning
NEW TANKS — Rick DiZinno (270) 826-9000 ext. 2601 EXISTING TANKS — Jordan Pyles (270) 826-9000 ext. 4601
Bird droppings have been known to contaminate water supplies. A 1993 incident in a small Midwestern town resulted in seven deaths and multiple hospitalizations for gastroenteritis. The town’s water tower had an improper roof vent and an uncovered hatch – allowing birds, bird droppings, and other contaminants to foul up the water.
It’s not uncommon to find dead birds in or around water tanks. If a screen is missing or broken or there’s a hole big enough for birds to fly through, a bird will likely become caught in the tank and eventually die. Once inside a tank, animals have a difficult time finding their way out. Tanks are confined spaces, and above the water line can hold toxic gases, fatal to humans and animals if there’s prolonged exposure.
Dead birds were found in a pair of Ohio water tanks five years after city officials received a report that the tanks needed repairs due to metal corrosion and evidence of animal intrusion, according to a Cincinnati ABC affiliate. Residents didn’t find out until the Ohio EPA temporarily shut down the tanks after finding issues.
Inspect tanks regularly to check for any unwanted visitors. If any problem areas crop up, it’s better to address them early on before there’s an even bigger issue with contaminated water. •
