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1. What does ASTM stand for?
2. ASTM F2160 vs. D3035, D2239 or D2447?
3. What is the difference between UL certified resin and ASTM F2160 resin?
4. Why can't I get SDR 11, UL listed conduit?

ASTM is the American Society for Testing and Materials. It is an association of manufacturers, engineers, consultants and governmental officials who write standards for all sorts of building materials, from cement, to steel and plastic pipe. Other important specification writing bodies are NEMA (National Electrical Manufacturers Association), UL (Underwriters Laboratories) and NEC/NFPA (National Electric Code/National Fire Protection Association).
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ASTM F2160 and D3485 are ASTM standards specifically written for conduit products. ASTM D3035, ASTM D2447, ASTM F714 and ASTM D2239 are ASTM water pipe specifications often referred to in conduit specifications. Dimensionally pipes conforming to ASTM F2160 and the various water pipe ASTM standards are the same, but the material specification for water pipes is much more stringent because it is for pipes under pressure vs. conduit pipes that are not under pressure. Using water pipe ASTM's for conduit can raise the price significantly because pressure rated resin is more expensive than conduit non-pressure rated resins. See the PPI Technical Note explaining the differences in specifications and the Flow Chart to choose the proper specification for power or telecom conduit.
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Not much in reality. Resins can have either or both classifications. Both are quality resins and the properties are very similar. However, a manufacturer is bound to run the particular resin that was tested and certified by UL. Blending or mixing is not allowed by UL standards.
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UL, Underwriters Laboratories, has strict guidelines that require pipe manufacturers to exactly manufacture according to the UL specifications. UL 651A*, Continuous Length HDPE Conduit, and UL 1990, Nonmetallic Underground Conduit with Conductors, have four categories of pipe thickness: EPEC A, EPEC B, Schedule 40 and Schedule 80. SDR11 is not a wall thickness dimension ratio listed and therefore not allowed within the UL listing.

When HDPE conduit is used in directional drilling, a heavier pipe is required. In 1¼" diameter through 3" diameter, a schedule 80 pipe will match up very closely to SDR 11 wall thickness and provide the extra pull strength required.

*In early 2012, UL has changed the standard numbers for plastic electrical conduit. Previously UL 651B was the standard for Continuous Length HDPE conduit. UL 651A was the standard for PVC and HDPE stick conduit. NOW:

1. UL 651 A is for continuous length AND stick HDPE conduit
2. UL 651 is for PVC conduit

NEMA revised their Polyethylene Conduit Specification NEMA TC7 in 2011. NEMA TC7 has SDR 11 in the specification as well as new standards for pipe stiffness and compression. ASTM F2160 for power and communication conduit as well as ASTM D3485 for Cable in Conduit (CIC) both have SDR 11 specifications.
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