Thinking about how to know the quantity left in the fresh water tank and I came up a couple of flow meters that should keep track of the water used and water remaining. I'm thinking that as long as the tank is filled and the system reset, this would be an accurate way to keep track. I don't know if the alarms integrated into these would be useful, since they work with large volumes.
Question: Which flow numbers would be best? Both of these are under $40 and are self powered.
FM-2
Min 0.08 g/min max 1.58 g/min
This has only 1/4" fittings but that might be enough.
or
DigiFlow Meter 6000R
Min 0.45 gpm Max 4.10 gpm
This one has 3/8" fittings.

Question: Which flow numbers would be best? Both of these are under $40 and are self powered.
FM-2
Min 0.08 g/min max 1.58 g/min
This has only 1/4" fittings but that might be enough.

or
DigiFlow Meter 6000R
Min 0.45 gpm Max 4.10 gpm
This one has 3/8" fittings.
