The 1973 GMC Motorhome was—and still is—a sight on the road today. This groundbreaking RV was just as interesting as its sleek body, with a V8 powering the front wheels and a spectacularly 1970s interior. And because it was the early ’70s, we had a different notion of what was okay to spray into the atmosphere as you drive. Like sewage, which an obscure option allowed this GMC to do.
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. That’s a euphemism for the raw sewage, which accumulates in an onboard tank and has to be disposed of at dumping stations. It’s as gross as it sounds, and it’s why someone at RV accessory manufacturer Thetford Corporation thought there had to be a better way. And so, the Thermasan was born.
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. A screen prevented solid waste from entering and clogging the system, which would’ve been hellacious to fix. Amusingly, Thetford called the exit an “ejection orifice.” The jokes write themselves.