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Liquid containment applications could all benefit from a little research, here are a few questions from professionals and DIY installers. Frequently Asked Questions about plastic tanks.

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Table of Contents

  1. What to Consider, Metal, Fiberglass, Bolted, Welded? - 500,000 gallon Drinking Water Tank; Potable Water Storage
  2. How do I determine the right material for the chemical I need to store... ?
  3. Where can I find chemical resistance data... ?
  4. Why don't tank manufacturers provide chemical resistance data... ?
  5. Who can you depend on ... ?
  6. What is a tank adapter... ?
  7. When is it time to retire a tank... ?
  8. Are fiberglass tanks are safe for drinking water?
  9. How do I keep the water fresh in plastic tanks, and not go green?
  10. Does the gasket material on the compression vary with application?
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

  Bolted Steel tank for Potable   (Drinking water storage)        frp tank - blue.jpg (11072 bytes)Fiberglass Tank for drinking water storage to NSF requirements.

 

a)       Which is less costly, steel or fiberglass or other.

 
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.
 

How do I determine the right material for the chemical I need to store... ?

Chemical resistance charts confirm compatibility of tank material to chemical, to some extent.

Caveats:

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

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Where can I find chemical resistance information on chemicals... ?

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.

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Why don't tank manufacturers distribute chemical resistance charts... ?

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.

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Who can you depend on... ?

Yourself, we can help, but you have to make the final decision.

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What is a tank adapter...

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)

 

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When is it time to retire a tank ... ?

Depends on the application, the more aggressive the  liquid being stored the more consideration to tank life span, inspection cycles and replacement consideration.

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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.

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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.

 

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Alltankscom LLC, ask for Art Snow at 800 537 9444  or  

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01/17/2012