When it comes to the storage of water
in tanks up to about 15,000 gallons, plastic tanks have just
about become the default selection. Other types of tanks
such as fiberglass, metal and concrete are bypassed more every
day due to the reliability of plastic tanks and their relatively
Algae growth in stored water can be a
problem if the UV rays from sunlight can access the water.
The 'natural' color of many plastics including polyethylene is a
translucent milky white. Most plastic tanks are produced
in this natural color because it allows the level of the liquid
to be seen. The translucent tanks are not the best for
water storage. When selecting a tank for water storage,
choose one that has opaque colors. The most common colors
for plastic storage tanks are a forest green and black.
Each of these does a good job of blocking out the UV rays from
Unless you have an unusual application
that requires the use of high temperatures or another special
property, polyethylene is a natural choice. Be sure to
select a polyethyelene that is not XLPE (crosslink polyethylene)
since crosslink polyethylene is not FDA approved for potable
water. HDPE or any linear polyethylene is appropriate.
Plastic tanks are rated by the specific
gravity of the liquids they are rated to hold. That
basically translates as 'tanks with thicker walls can hold
heavier liquids'. Common tank ratings are 'water only'
(1.2 SG), 1.5 SG and 1.9 SG. When you are storing water,
you can use the 'water only' tanks. They are usually rated
at 1.2 specific gravity but may not actually state that.
'Water only' tanks are made for storing water and usually do it
well and for a long time.