The Overland Mark 2 (Mark 2) was designed to support a crew of six and operate unsupported for a short period of time. The Mark 2 had a cold and hot water system that supplied water to the kitchen and a lavatory for washing hands and meal preparation. However, the water was not used for flushing the toilet. I’ll talk more in-depth about that in my book.
The Mark 2 contained 2*100 gallon water tanks. These tanks provided water under gravity to the hot water heater and the rest of the system. Water lines traveled underneath the insulated flooring. The drawing below shows that only one tank fed the hot water heater. Depending on the line pressure, it may be possible that the second 100-gallon tank could have also provided supply too. There is no mention or diagram of a wastewater system. It is entirely likely that the greywater from lavatory hand washing and the kitchen sink was drained outside as it was used.