1. Those are HORIZONTAL tanks.
2. The level gauge is a FLOAT designed Gauge
3. Makes NO difference if tank on or off.
4. REGULATOR REPLACEMENT???????????????????????????????? WHY
5. Yes, if OVERFULL the gauge may do that
6. If tank upside down it will do that Rotate 180 degrees and see what happens
7. Sometimes a float can get "stuck" inside the cylinder. Remove the cylinders MAKE SURE they are really full. Then lay down or rotate 360 degrees a few times to free up stuck float.
8. This is the BEST and ONLY type level gauge system that always works, as it uses a inside float to gauge fluid level. It is the same design used on ASME motorhome tanks. Doug