Assessing Water Quality Impacts of Wildfire-Induced Depressurization in Water Systems: VOC Analysis Results

Wildfire can cause localized depressurization in water distribution systems (WDS), introducing combustion gases that can contribute to volatile organic compound (VOC) contamination. This study evaluated VOC transfer into high-density polyethylene (HDPE), polyvinyl chloride (PVC), and galvanized steel pipes during controlled compartment fire exposures. VOCs were detected in both liquid-phase condensate and pipe leachate samples, confirming that back-siphoning of combustion gases can cause contamination regardless of pipe material. In some cases, pipes that appeared visibly undamaged leached VOCs exceeding federal maximum contaminant levels (MCLs). Polymer pipes yielded higher VOC concentrations than the galvanized steel, suggesting that multiple mechanisms (including adsorption, deposition, and thermal material degradation) contributed to VOCs detected, as metal materials are largely inert at the temperatures reached. Polymer pipes close to the compartment deformed before reaching critical threshold temperatures for VOC leaching indicating that when VOC concentrations in the pipe leachate exceeded federal MCLs multiple mechanisms, not just contaminant release from material degradation, were contributing. Post-exposure flushing reduced but did not eliminate VOCs in polymer pipe leachate samples. Subsequent stagnation significantly increased VOC leaching, emphasizing the risks of incomplete system recovery. These findings demonstrate that back-siphoning during depressurization can compromise WDS safety and that post-fire systems may retain VOCs when no damage is visible.