From Tim Heintz – posted in the Tin Can Tourists Facebook group:
Sometimes even I find interesting tidbits of trailer history in various magazines hidden in the smallest little articles. Here we find in a 1956 Magazine the earliest known mention of a complete ‘Black Tank‘ system for travel trailers. Believe it or not it was legal before (and a bit after) this time period to dump black water straight on the ground, it was recommended and sometimes required by the ‘best’ parks to at least dig a hole under your trailer first. There are few records of very crude custom built metal tanks for black water that predate this 1956 article but even those being factory built options were less than desirable to use as there was no smell-less venting, low water usage toilets, leak proof valves or even dump hose attachments.