The Life Expectancy of a Polyethylene Storage Tank

Polyethylene tanks are excellent for many environments and applications with a need to store a very wide variety oils and automotive style fluids.

Poly tanks can handle extreme temperatures below zero. They show minimal distress in most air temperatures up to 120 degrees F. However, temperatures over 120 degrees F will begin to soften the tank walls and may compromise the integrity of the tank.

Rotationally molded poly tanks ranging from 6.5 to 12,500 gallon capacities. They can accomodate small fluid storage needs, to bulk fluids in a cylindrical vertical tank or square storage tanks. Typically, poly tanks are single walled, and offer many benefits in comparison to steel tanks. We'll discuss the benefits in another post, but overall, poly tanks often have a less expensive price tag and have a longer life expectancy. Depending upon the shape, the tank may offer additional benefits, such as being manufactured with extra strength corrugated tank walls, or may be configured into a stackable system that can store multiple fluids in a single footprint. For example, the Tote-A-Lube poly tanks are available in several capacities and are stackable up to 4 tanks in a single system depending upon the tank capacity. Here at Proformance Supply, we believe the 130 gallon Tote-A-Lube Tank system features the most benefits when stacking fluids. 

Life Expectancy of Plastic Tanks:
There is not an overall proven way to determine the life span of a polyethylene tank. Many variables will effect a tank's lifespan, as the list below illustrates. It is wise to discuss your expectations and intended use with the tank manufacture, and ask any questions you believe may impact the service life of the tank.

• Are chemicals being mixed in the tank?
• What is the temperature of the fluid or oil stored in the tank?
• What is the specific gravity of the chemical being stored in the tank?
• Were extra fittings added to the tank? If yes, are the fittings large or small?
• Are there accessories attached to the tank walls?
• Is there any external fill or vibration on the tank?

We should also address the mobility of a tank upfront. Do you needs depend on a stationary fluid storage tank system, or is tank mobility an attractive fluid dispense feature? Mobile tanks can feature caster wheels or fork lift pockets, and in addition, dispense equipment is sometimes attached directly to the tank via steel brackets located on top of a tank. However, the more often a tank is moved around the shop, the more physical strain the tank is exposed to, from lifting, loading and from the physical movement of the tank.

Another factor that weighs on on a tank's overall life expectance are weather attributes. Is the tank being stored outdoors? Generally, tanks that are used outdoors in southern climates are subjected to more intense sunshine than they are in northern climates. Even though the polyethylene resins used in most roto-molded poly storage tanks have UV inhibitors in them, UV rays will still have a negative effect on the life span of any polyethylene tank.

Roto molded tanks have been on the market for quite some time, at least for nearly 40 years. We have gained a good general insight into what the average life span of a roto molded polyethylene tank will be. But due to many unknown factors to each environment and fluid application as outlined above, a tank's life span can vary. Many storage and dispense applications are very tank friendly, and therefore the tanks have an unusually long service life. Other applications can be very demanding, limiting the tanks to a short service life as a result. On rare occasion, we have seen tanks fail in less than two years and we have seen others well over 30 years.

Although a guarantee cannot be made on how long a polyethylene tank will actually last, we know from experience, that the average storage tank will last around 20 years, depending on some of the above factors.

General Tank Warranties:
Warranties on storage tanks will vary from manufacture to manufacturer. Each tank warranty can very from 3 years to a lifetime. It is best to consult each manufacture on what their warranty is and what it covers.

How Do You Determine If A Tank Is Still Safe For Use?
As a fluid storage tank is begins to show its age, you will be able to see fine fissures or hairline cracks. Inspect each tank for any cracks or wear marks. These fine cracks will become more intense and visible as time goes on and will become stress cracks. Dropping a light inside the tank can be helpful in visual examinations, because a stress crack will be easier to spot with an internal light source in place. A tank beyond its life expectancy will also sound dull when struck and could crack on impact as a result. Regular, annual documented tank inspections should be a normal part of your shop safety and maintenance program. When a tank is showing signs of wear or is otherwise determined to be unsafe, it is best to replace it.