Permeation of Petroleum-Based Hydrocarbons through PVC Pipe Joints with Rieber Gasket Systems

There is significant concern in water utilities regarding the permeation of petroleum-based hydrocarbons from contaminated sites through potable drinking-water pipes made of polyvinyl chloride (PVC). Previous studies have addressed the impacts of hydrocarbons on the pipe materials, but the impacts of the hydrocarbons on gasket materials joining and sealing the pipes have not been investigated. This study investigated the permeation of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds through PVC pipe joints equipped with 50-mm styrene-butadiene rubber (SBR) and nitrile-butadiene rubber (NBR) Rieber gaskets exposed to various levels of gasoline contamination. Results of permeation experiments with premium gasoline indicated that permeation occurred only through the gaskets and not through the intact pipe materials. For experiments with premium gasoline, benzene was the first compound detected with a breakthrough time of approximately 21 days. However, for experiments with various gasoline concentrations in water, including water saturated with gasoline, no significant amounts of BTEX compounds were detected in the pipe water after 9 months of exposure. The steady-state permeation rates of benzene when exposed to premium gasoline were found to be $0.73\pm 0.29$ and $0.38\pm 0.32\mathrm{mg}/\mathrm{joint}/\mathrm{day}$ for SBR and NBR gaskets, respectively. The corresponding diffusion coefficients of benzene in SBR and NBR gaskets (which have not been reported before) were determined to be $1.1\times {10}^{-7}$ and $6.0\times {10}^{-8}{\mathrm{cm}}^2/\mathrm{s}$, respectively, by curve fitting the permeation data with a diffusion model. Although PVC pipe joints were found to be permeated by free-product gasoline, water flow in pipes would dilute the benzene in drinking water to below the maximum contamination level (MCL) of $5\mu \mathrm{g}/\mathrm{L}$.