Every once in awhile you stumble across a gadget that is more useful; than you imagined.
A bit ago I was looking at my FW tank trying to figure out if it was really full when the autofill shut off and than do a calibration if needed. The problem was I had no idea how much water was going into the tank from empty. I starting looking around for some sort of water flow meter/totalizer that wasn't of the commercial grade I've used in the past. Found this item on Amazon"
https://www.amazon.com/gp/product/B0058EOC5M/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1so I grabbed it figuring at that price how could one go wrong. It has two totalizators, one of which automatically resets to zero after a period of no activity and the other must be reset manually. I did find out the tank takes 88 gallons before shut off but now I use it all the time for flushing the BW tank, looking at the water softener volume before regen (if you know you incoming grains the cycle can be calculated).
Since I eliminated the standard kinky water hoses I now use the tank exclusively and this help keeps track of how much FW I have on board, subtract out the GW tank level and viola you know just how much went into the BW tank (that level sensor has never been accurate).
Anyway, it's a handy gadget and has been a lot of fun just gathering information.
