Liquid containment applications could all benefit from a little research, here are a few questions from professionals and DIY installers.
Please send us your questions, they help us all grow and create and "get it right the first time". Suggestions by Gene Vincent....
- What to Consider, Metal, Fiberglass, Bolted, Welded? - 500,000 gallon Drinking Water Tank; Potable Water Storage
- How do I determine the right material for the chemical I need to store... ?
- Where can I find chemical resistance data... ?
- Why don't tank manufacturers provide chemical resistance data... ?
- Who can you depend on ... ?
- What is a tank adapter... ?
- When is it time to retire a tank... ?
- Are fiberglass tanks are safe for drinking water?
- How do I keep the water fresh in plastic tanks, and not go green?
- Does the gasket material on the compression vary with application?
Is the contents of
your tank flamable? if so what are legal requirements
What to Consider, Metal, Fiberglass, Bolted, Welded? - 500,000 gallon Drinking Water Tank; Potable Water Storage?
Thanks for the opportunity, I am very pleased to respond to request for information
a) Which is less costly, steel or fiberglass or
Fiberglass in this size is not available in technology that I consider viable. (cable wrap and an interlock plate style have not proved durable over the long term and have considerable drawbacks) 100,000 gallons in fiberglass is about the max, one piece tank)
b) Which type of interior and exterior coatings are less costly: Epoxy, or other? If the tank is epoxy construction, than an epoxy paint coating would be unnecessary, right?
To my knowledge there are no tanks made entirely of epoxy. However I have heard a few people refer to fiberglass as epoxy. Two part epoxy is better a better paint system (it has a hardener) than regular paint for interior on water tanks; interior coatings require a lot of surface preparations, and can be quite expensive to do correctly in the field.
c) Of steel construction. Is welded construction less costly that bolted construction?
Bolted has advantages over welded, but does have a drawback of requiring periodic gasket replacements. Bolted tank staves have the advantage of being pre-coated inside and out, really great for water. But I think you installed cost will be more with bolted.
d) Which type of tank lends itself to the least costly Non destructive testing?
Metal tanks and coatings on same can be tested, but you should expect many years of maintenance free service in either welded or bolted.
e) Which type of tank overhead cover is least costly: Fixed, floating, any type of flexible floating heavy duty tarps, similar to a swimming pool cover? Would such a cover satisfy AWWA requirements for potable water?
Closed top tanks are definitely less problematic that floating roof tanks, which are a constant maintenance issue. I know AWWA approves closed top tanks, but have no knowledge of their acceptance of floating roof tanks.
f) Do the corrugated style tanks satisfy AWWA requirements for potable water?
Corrugated stops at 150,000 gallons and while it is galvanized steel, the galvanized part is not acceptable to FDA, so it is necessary to coat the inside with and epoxy NSF approved. Corrugated is a bolted steel style tank.
My vote would go to bolted steel tanks...
Stephen, thanks for the questions, let me know if we can help you and please let us know what you need a price for and where the tank would be installed.
Chemical resistance charts confirm compatibility of tank material to chemical, to some extent.
a. higher temperature reduces a materials chemical resistance
b. chemical compounds are not discrete and may reduce a materials chemical resistance
c. a discrete chemical may start out resistant, degrade and become less resistant
1. The best source of information on the correct storage container comes from the equipment manufacturer and their MSDS, Material Safety Data Sheet, produced by the chemical manufacturer.
2. NACE, National Association of Corrosion Engineers, has many resources available. http://www.nace.org/
3. American Institute of Chemical Engineers, http://www.aiche.org/ chemical engineering and chemical resistance resource.
a. The responsibility for tank material selection must rest with the client, as only through the process of 'due diligence' research and awareness of the chemical potential for cause and effect on materials can the correct material be selected.
Yourself, we can help, but you have to make the final decision.
Any tank fitting that allows for the piping, plumbing or process connection, this could be NPT (national pipe threads), ANSI Flanges, Tri clover (food grade special fitting)
Depends on the application, the more aggressive the liquid being stored the more consideration to tank life span, inspection cycles and replacement consideration.
I was wondering if fiberglass tanks are safe for drinking water. Any info on this would be appreciated.
Hugh Mc Guigan - June 2008
Hello Hugh, the answer is some of them, a fiberglass tank need to be specifically designed for drinking water from the beginning.
The correct resin should be selected, a resin that has FDA or NSF certificates
Once the tank is built, it needs to be steam cured for 24 hours with the correct volume of steam, at a correct temperature and the steam exhausted from the tank. This procedure seals the interior of the tank by off gassing styrene.
Again a ASTM, FDA, NSF certified procedure.
How do I keep the water fresh in plastic tanks, and not go green?
Wilton Jackson - June 2008
White plastic tanks are the perfect container to grow algae, however algae is very hard on the human digestive system.
If you want to stop Algae, Black plastic tanks are opaque and keep algae from growing by keeping the suns rays from making contact with your water.
Placing white tanks indoors will also vastly reduce algae growth, artificial light will grow algae at a slower rate, but it will grow indoors in a white tank.
Treating the water with a small amount of chlorine will also keep algae from growing, but adds a little something to the taste.
Algae is a plant and will begin to grow in untreated water within 72 hours of exposure to direct sunlight.
Does the gasket material on the compression vary with application?
Chemicals and petroleum products have a vary different effect on gasket materials, always check with your chemical manufacturer to confirm viability of the proposed gasket material.
COMMON DO'S AND DON'TS WITH POLY TANKS:
Do not over-tighten tie down straps or bands which may cause excessive stress on the tank. A "snug" fit is best.
Do not attach heavy valve and plumbing fittings on a bulkhead fitting without proper support. Always use flexible connections to allow the tank to expand and contract.
Always water test the tank before using to be sure fittings are sealed tight.
Do not over-tighten the bulkhead fitting. Fittings are installed to proper torque ratings at the time of manufacturing but may become loose through movement in shipping. When you get your tank, hand-tighten the fitting and then give it 1/4 of a turn to make sure it's tight.
WHAT MATERIAL IS USED TO MAKE YOUR TANKS?
A linear, high-density polyethylene resin provides outstanding environmental stress crack resistance. The resin is UV stabilized but by keeping the tank sheltered or indoors you will prolong the life of your tank. Click on the following link for specific information regarding the resin used to manufacture above ground tanks. Resin Information
ARE YOUR TANKS FDA APPROVED AND IS IT SAFE TO STORE WATER IN AN ABOVE GROUND TANK?
Yes, it is safe to store water in our above ground tanks and below ground cistern tanks shown on our website. The resin used to manufacture these tanks meets FDA specifications for safe storage of potable water. Click on the following link for specific information regarding the FDA status of the resin.
ARE YOUR ABOVE GROUND TANKS NSF APPROVED?
NSF International, founded in 1944 as the National Sanitation Foundation, is known for the development of standards, product testing and certification services in the areas of public health, safety and protection of the environment. We have the NSF certification, from specific plants, for our potable water tanks.
The NSF certification process is done on a plant by plant basis. We currently have select tanks that are certified NSF approved in our Tooele, UT; Washougal, WA and Hanford, CA manufacturing plants. For further details, please give us a call.
The resin that we use to manufacture our above ground tanks is considered an NSF approved resin. Click on the following link for information regarding the NSF status of the resin. NSF status of resin
DOES THE COLOR OF A TANK HAVE ANY SIGNIFICANCE?
Generally, colors are used to designate one grade of tank from another and is for production identification only except for Water Only tanks. Our standard color for premium weight tanks is a natural or white and for heavy duty tanks is it light blue. Do not be misled into thinking that a color increases the life expectancy or UV resistance of a tank.
CHEMICALS CAN I STORE IN THE TANKS?
Several fertilizers and chemicals can be stored in our above ground tanks. We strongly recommend that you contact the chemical manufacturer to see if their product is compatible with high density, linear polyethylene. If they cannot answer your question, call our Customer Service department and they will be happy to research it for you. Try to have as much information available as possible such as the temperature of the product, the percentage of product (Ex: Hydrochloric Acid, 50%) etc. We have a link for our chemical resistance guide due to the infinite range of chemical combinations, concentrations and temperatures.
ATTENTION: THIS GUIDE IS GENERAL ONLY, FINAL APPROVAL SHOULD BE OBTAINED FROM YOUR CHEMICAL PROVIDER!!!
STORAGE PETROLEUM PRODUCTS IN THE TANKS?
We recommend that you do not store petroleum products in our tanks because they will soften the tank walls.
STORAGE OF CHEMICALS OR FERTILIZERS IN THE BLACK OR DARK GREEN WATER STORAGE TANKS?
No, these tanks are designed for water storage only. They are rated at 8 pounds per gallon.
CAN I USE AN ABOVE GROUND TANK FOR THE STORAGE OF BIODIESEL?
Biodiesel is approved on a case by case basis, B100 may be stored with stainless steel fittings and viton gaskets... please contact us to discuss this application.
SPECIFIC GRAVITY, HOW MANY POUNDS PER GALLON WILL YOUR TANK HOLD?
There are two grades of polyethylene tanks - premium and heavy duty. The premium weight tank has been designed and is manufactured to meet a specific gravity of 1.5, equaling 12.5 pounds per gallon at 73 degrees F. The heavy-duty tank has been designed and is manufactured to meet a specific gravity of 1.9, equaling 15.75 pounds per gallon at 73 degrees F. (An increase in liquid temperature will substantially decrease the specific gravity rating!)
WHAT IS THE WALL THICKNESS OF YOUR TANKS?
We refer you to the paragraph above that relates to specific gravity/pounds per gallon. Because the wall thickness varies from top to bottom on a tank, it is not the best gauge for determining the quality of a tank. The very bottom of the tank is the thinnest part of the tank and is made that way to flex when the tank is empty or full. Generally the wall becomes thicker as you go from the top to the bottom of a vertical tank. This is done to increase resistance to head pressure created by the height of the liquid in the tank. The radius of the tank is thicker to increase strength where it is most critical. The actual weight of the tank is also not a good comparison when shopping for tanks. Just because a competitor may use more material in the tank does not make it a better tank. That is determined by the resin, mold design and the steps taken during the rotomolding process.
MAXIMUM TEMPERATURE THAT YOUR TANKS WILL WITHSTAND?
Polyethylene storage tanks have a maximum storage temperature of 140 degrees F. Contents with a temperature in excess of 140 degrees F-even for a short period of time-can weaken the tank's structural integrity and make it susceptible to deformation and failure.
WHAT WILL HAPPEN TO MY TANK IF I LEAVE IT OUTSIDE IN FREEZING TEMPERATURES?
The tank itself does not have a minimum temperature rating. If you plan to keep the liquid in the tank and you know that it will freeze, make sure that you leave room for expansion. The most likely part to crack on the tank is the bulkhead fitting which can be easily replaced.
HOW MANY YEARS WILL MY TANK LAST?
There is no good way to determine the life span of a polyethylene tank. Many variables can have an effect on the tank - what type of material is being stored in the tank? Is the tank used indoors or outdoors? If the tank is outdoors, what part of the country are you located in? Tanks used outdoors in Arizona or Florida are subjected to more intense sunshine than in Minnesota for example. UV rays will have a detrimental effect on the life span of any poly tank. Is the tank being used strictly for stationary storage or for transport? Each of these factors will have an effect on a polyethylene tank.
I HAVE A TANK THAT IS SEVERAL YEARS OLD. HOW CAN I DETERMINE IF IT IS STILL SAFE FOR USE?
If a tank is beginning to show its age, you will be able to see fine fissures or hairline cracks referred to as crazing. Look for crazing on the dome of a vertical tank in the area where sunlight is most intense. The top of a transport tank, which has been allowed to set outside all year, is a good place to look as well. These fine cracks will become more intense and visible as time goes on and will become stress cracks. Giving the tank a good hit with a baseball bat is as good a test as any. The resilience of a good tank will be obvious. A tank beyond its life expectancy will sound dull when struck and could crack as a result. It is better to check early and be safe versus losing valuable chemicals and incurring cleanup expense. When a tank is determined to be unsafe or you know it is getting old, it is best to make it a non-drinking water only tank.
HOW SHOULD I PLUMB MY TANK?
Rigid piping must not be connected directly to a tank. Flexible connections are required between the tank fitting and the pump to allow for expansion and contraction of the tank as it is filled and as liquid is withdrawn. A good quality flexible hose is best. We also recommend proper support under heavy valves and fittings that may be attached to the tank fitting. Please refer to the warning labels on our tanks for details. These plumbing recommendations will also extend the life of the tank by reducing stress on the tank. Please consult us for valves and fittings are recommendations for all compatible plumbing requirements.
Take a look at our pictures section for suggestions
HOW TIGHT CAN I TIGHTEN A BULKHEAD FITTING?
When bulkhead fittings are installed at the factory, a torque wrench with a special adapter is used to tighten them. Sometimes the fittings loosen and it may be necessary to tighten them. Without a torque wrench, our recommendation is to hand tighten the nut and then give it another 1/4 to 1/2 turn. Do not over tighten as this may pinch the gasket and cause the fitting to leak. Some fittings are turn right to tighten and some are turn left, please note and adjust as needed.
CAN YOUR TANKS BE PRESSURIZED?
No, our tanks cannot be pressurized.
CAN YOUR TANKS BE BURIED?
Tanks specifically designed for above ground use cannot be put underground. If it is put below ground, the weight of the earth around the tank will cause the walls to collapse. We do make septic and cistern tanks that are designed to be buried. See "Water & Waste Tanks" under Main Links.
WHAT TYPE OF SURFACE IS REQUIRED FOR PLACEMENT OF A VERTICAL TANK?
Inspect the surface to ensure a smooth, level area that will supply full bottom support. A properly constructed concrete pad that is capable of supporting the contents of the tank is the best support and is recommended above 2,000 gallons. Other materials such as very flat blacktop, or contained, packed sand or pea gravel have been used successfully. All surfaces must maintain uniform support through freeze/thaw, erosion and other disturbances.
CAN I PAINT MY TANK?
Painting a tank is not something that we recommend but we know that it is frequently done. Once painted, the tank would not be covered under our normal warranty. Based on what distributors and customers have told us, to prepare the tank for painting, wipe it down with a paint thinner to remove any oily residue. The paint that seems to adhere the best is an automotive urethane which is commonly used to paint car bumpers. Keep in mind that over time, as a tank expands and contracts, the paint will usually crack and will need to be reapplied.
DO I NEED TO CLEAN MY TANK BEFORE USE AND IF SO, HOW DO I CLEAN IT?
If you are planning on using your tank for potable water storage, you may want to rinse it with a very mild bleach solution to sanitize the tank and then rinse it again with clean water following the bleach solution rinse.
DO YOUR PRODUCTS REQUIRE A MATERIAL SAFETY DATA SHEET (MSDS)?
No, our products are exempt from the MSDS requirements established in the Hazard Communication section (29 CFR 1910.1200) of the Occupational Safety and Health Administration (OSHA) regulations. Our products are classified as articles as referred to in 1910.1200(b)(6)(v) and as defined in 1910.1200(c).
1910.1200(c) Definitions"Article" means a manufactured item other than a fluid or particle: (i) which is formed to a specific shape or design during manufacture; (ii) which has end use function(s) dependent in whole or in part upon its shape or design during end use; and (iii) which under normal conditions of use does not release more than very small quantities, e.g., minute or trace amounts of a hazardous chemical (as determined under paragraph (d) of this section), and does not pose a physical hazard or health risk to employees.
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