Permeation of gasoline through DI pipe gaskets in water mains

Sorption tests and pipe-drum experiments were conducted to study permeation of monoaromatic compounds in gasoline through five types of ductile-iron (DI) pipe gaskets. Among the materials tested, ethylene propylene diene monomer (EPDM) had the highest sorption of premium gasoline, and fluoroelastomer rubber had the lowest. The gasket-heel portion sorbed less gasoline than the bulb portion, indicating that the heel portion was more resistant to permeation. For gaskets exposed to premium gasoline, pipe-drum experiments showed the breakthrough order of benzene toluene ethylbenzene xylene compounds was EPDM > chloroprene rubber congruent to styrene butadiene rubber (SBR) > nitrile rubber (NBR). For DI pipes with SBR gaskets exposed to premium gasoline, the benzene concentration after 8 h of stagnation exceeded the maximum contaminant level (MCL). With typical water flow rates in pipes, the estimated benzene concentration did not exceed the MCL. If pipes are to be installed in gasoline-saturated groundwater, NBR gaskets are preferred over SBR gaskets.