Q. Can you use the Water Flow Meter on a gravity fed tank?

A. If your tank is mounted high and you have good water pressure, yes. However if the pressure is low then it is not recommended. 

Q. Can I use the Water Flow Meter at the end of my hose?

A. Yes you can, it is possible to install the Water Flow Meter at the end of the hose under the spray gun. However it will need to be installed upside down.