@Colin_T … I had left water on a couple times last year, so I’m really losing my mind, or doing too many things at the same time… I have thought about some sort of float valve, but would have to change a few things… I currently fill at my filter barrel, closest to the water source, and it would be tight to fit a mechanical float valve in it, with a full sized cast iron sump pump, that I use to pump water around, and a 6 gallon bucket, that I used as a filter media container, suspended inside the barrel, above the pump… the pump pumps water faster than what comes out of the hose… if I added some hose length, and filled at the highest tank, there would be plenty of room for a mechanical valve… but I would probably have to reduce the outlet some to unbalance the flow… I have everything balanced right now, so there really isn’t a spot that fills up 1st… each tank drains into the next lower one, through a hole above the water line… these aren’t sealed, as they are above the normal water line, and when I forget about the fill, water, it just leaks around those drain holes, in the lower tank, inches below the actual top of the tank, so no fish get washed out…
I have a blended hot / cold water spigot, but we developed a leak in the shower upstairs, that we only use for company, so I have a hot water line valve shut off there, but that also feeds my outside spigot, so this year I only have cold fill, until I get the upstairs leak fixed ( it’s actually a drip, inside the shower, the faucet won’t shut off completely ) and since it’s only for company use, and we rarely have company, I just haven’t gotten it fixed yet… I didn’t remember that it also fed my outside line…
Having blended water, doesn’t fix my mental deficiency, but does keep the tanks from getting so cold, so quickly… but I did run the house out of hot water, a couple times last year, which prompts Mrs to yell at me ( as my alarm )