Ethanol -UST
Ethanol Compatibility with Fiberglass UST Systems

E-10 Compatibility
Due to state bans on methyl tertiary butyl ether (MTBE), notably in California and New York, the use of ethanol motor fuel (i.e., a maximum of 10 percent ethyl alcohol in gasoline) has expanded. However, other states, particularly in the Midwest, have used ethanol fuel for many years. The market share of ethanol motor fuel has grown from virtually zero in 1978 to 7 percent in 1986, and is approaching 100 percent today. Although this represents a significant volume of ethanol stored and dispensed through the pre-1978 population of underground storage tanks (USTs), it is comforting to know that fiberglass USTs and piping that store conventional gasoline or MTBE added gasoline should perform equally well when handling gasohol.

While it is natural for those of us in the petroleum marketing industry to focus on UST compatibility with ethanol, the introduction of ethanol into the marketplace raises many other considerations. First, with vehicle turnover averaging 20 years or more, there are both old and new automobile fuel handling systems that must be compatible with oxygenated motor fuels and additives. For this reason, the U.S. Environmental Protection Agency (EPA) provides consumer protection by limiting the amount of ethyl alcohol in motor fuel to 10 percent. If this EPA limit is exceeded, automobile manufacturers will void their warranties for non-flexible fuel vehicles.

Second, the elastomers in fuel dispensing equipment, other than tanks and piping, are often more vulnerable to fuel base-stock and additive changes. This includes Buna-N gaskets and “O” rings, and submerged metals such as aluminum, copper, and black or cast iron. Thus, for older equipment it is prudent to consult the manufacturer of dispensers, pumps, monitoring systems, nozzles and swivels when making changes in stored fuels.

Finally, EPA requires that methanol blends exceeding 5 percent methyl alcohol meet hazardous substance storage and piping requirements and be secondarily contained. Thus, all double-wall fiberglass tanks and piping have been manufactured for storage of 100 percent ethyl and methyl alcohol since 1988 for piping and 1990 for tanks.

Ethyl alcohol, because of its affinity for water, is not blended into gasoline until it is loaded into the delivery tank truck. American Petroleum Institute (API) member companies address the need to control the ethanol blend component in API Recommended Practice (RP) 1626 that states: “In-truck blending is not recommended since complete blending may not occur.” Thus, so-called “splash-blending” ethanol in tank trucks is not recommended since the ethyl/gasoline components tend to stratify and remain stratified after delivery to the refueling facility. As a result, the pump may pick up a high concentration of stratified ethyl alcohol, damage the automobile engine and not be covered under warranty.

This affinity of ethyl alcohol for water is a strong reason to follow API RP 1621 and remove water from tank bottoms when the water exceeds one inch. While ethanol can safely absorb 0.5 percent ethyl alcohol into a solution, the water reduces the motor fuel BTU content and octane rating, again affecting the consumer. When ethanol absorbs more than 0.5 percent of alcohol, a “phase-separation” will occur as the alcohol begins to drop out of the gasohol solution into the water bottom of the tank. This phase-separated alcohol/water bottom encourages the growth of aerobic bacteria colonies, which are detrimental to petroleum fuels and certain fuel handling components. Experience has shown that this is not a problem with fiberglass tanks and piping.

While gasohol entered the marketplace in 1978, UL did not include gasohol and methanol fuels in material compatibility testing protocol, until later. As a result, the UL listing for fiberglass tanks and piping included ethanol in 1981 and 1988 respectively (i.e., UL 1316 and UL 971). Thus in 1978, when gasohol was first introduced, there were some 100,000 fiberglass USTs in conventional gasoline service before the UL listing process included gasohol in their compatibility testing protocol. Therefore, the early users of fiberglass tanks and piping (i.e., major oil companies) and fiberglass tank and pipe manufacturers conducted independent studies to determine the effect of gasohol on the fiberglass material used for in-service USTs. It was determined that the fiberglass components used in pre-1981 tanks and pre-1988 piping were essentially the same as those subjected to UL compatibility testing and there was no technical reason to believe that the older USTs were not gasohol compatible. In 1992, Owens Corning, the manufacturer of the oldest fiberglass tanks, advised certain major oil companies that some tanks were approaching 30-years-old and the warranties have expired. As a result, the affected companies conducted surveys of these older tanks, including tanks in alcohol service (e.g., in the Midwest) and confirmed that the tanks were satisfactory for continued service. In summary, technical evaluations and historical experience demonstrate that there is no material or technical reason why properly installed pre-1988 piping and tanks in conventional or MTBE service should not perform equally as well when handling 10 percent ethanol blends.

E-85 Compatibility

Fiberglass piping:
    Underground fiberglass piping and fittings installed in service stations have been compatible with up to 100%-percent ethanol for over 40 years.
Fiberglass tanks:
  1. 1983 - The September 1983 issue of the Underwriters Laboratories (UL) Gas & Oil Equipment Directory includes multiple manufacturers with listings for fiberglass “non-metallic tanks for petroleum products, alcohol’s and alcohol-gasoline mixtures.” The UL use of the term “alcohol’s and alcohol-gasoline mixtures” is defined in UL standard 1316 to include fuels with any level of ethanol or methanol up to and including 100%.

  2. 1988 - In 1988, UL began listing underground fiberglass piping and tanks for 100% ethanol and methanol.

  3. 1990 – By 1990, Institute member fiberglass tank manufacturers had modified their tanks constructions to handle gasoline with any level of ethanol or methanol up to 100% for all double-wall fiberglass tanks and in some cases single wall fiberglass tanks.

  4. 2004 - UL did not include fiberglass piping or tanks in the 2004 suspension of UL markings for fuel dispensing
    devices that reference compatibility with alcohol-blended fuels containing greater than 15-percent alcohol.
Sullivan (Sully) Curran P. E., Executive Director
Fiberglass Tank & Pipe Institute

Sullivan D. Curran, P.E., is the Executive Director of the Fiberglass Tank and Pipe Institute.

  1. This paper discusses the compatibility of gasoline-alcohol blends with fiberglass storage tanks and piping systems manufactured by current members of the Institute, namely Ameron International - Fiberglass Composite Pipe Group, Containment Solutions Inc., Fiber Glass Systems and Xerxes Corporation. While this paper includes the Institute’s understanding on products from former members, it is not an analysis of products by other manufacturers.

  2. Institute tank company plants may have changed manufacturing specifications at different times within a given year listed above. In addition, certain tanks were manufactured according to customer specifications. Thus, tank owners needing specific production information, will need to provide the manufacturer with delivery date and delivery location.

  3. Nothing in this paper alters the given piping or tank manufacturer’s warranty for the product at the time of sale.

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