As an owner of a 2016 Fleetwood Expedition 38K, I have two toilets in the bath and a half layout. Both are porcelain. Without additional input from the OP on their unit, I'll offer the following:Mid toilet is a Dometic 311 Toilet. This is the low ...
Here is a great webpage that explains the components of an RV mountedpropane tank:RV Tank InnardsSeeing what is inside, can help you to determine what you are seeingoutside, and how to judge the gauges.