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GMC made a motorhome that pumped sewage through its exhaust on purpose

The classic 1973 GMC Motorhome had a gross, little-known option that let it spray sewage out the exhaust as you drove.

One of the options available for the GMC Motorhome was a system called Thermasan, which promised to improve on one of the worst parts of RV ownership: Black water. Helmut Reiss/United Archives, GMC via CarsWP.com The premise of the Thermasan “waste destruction system” was simple: Dump black water through the hot exhaust to sanitize and dispose of it. According to a maintenance manual for the 1973 model, this was done using a wiper motor-powered pump connecting the black water tank to the exhaust, where it was plumbed in just upstream of the muffler.

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