The top of the bag is shown as a dotted line and the fluid level is a thin line (I forgot to add the areas!)
Dimensions from Sasse, given by Philippe Vandevivere
The square box is the gas meter, filled via the funnel (gas bubbles up through water, as in a flame arrester, and causes a "wheel" to rotate which is detected by a reed switch). The loop of clear tube at the bucket is the gas takeoff, which is teed off the "safety valve" in the bucket below water surface so the gas cuts off at a given pressure for the burner (this will also give some burn back protection as the flame will be under water).
Gas Receiver (11.2/10-24 tractor front tyre)
The poly pipe fits over the valve stem (with a bit of insulating tape and a hose clip)