Most modern RV's have separate grey and blackwater tanks, but many older units (including the 1973 GMC RV) had a single combined tank. You sometimes still stil

Most modern RV's have separate grey and blackwater tanks, but many older units (including the 1973 GMC RV) had a single combined tank. You sometimes still still a combined tank on modern units, usually smaller ones. I don't know what you mean by "chemical toilets", I put digesting/deodorizing chemicals in my RV's black tank, does that make it a "chemical toilet"? Either way, the liquid I drain from the black tank is definitely what I would call "sewage".