1,000 upon 1,000 of 12v on demand pumps out there. every 4 wheeler utv/ atv, to pull behind sprays for riding lawn mowers. have these 12v on demand pumps. so when you pull trigger on the wand pump turns on and it sprays. let off trigger, pump turns off and no water is sprayed.
the tire filler tool. close valve on unit = 12v on demand pump shuts off. undo air bleed valve. wait a few seconds. close bleed valve. open fluid valve. pump turns on automatically.
turning the pump off. while air is being bleed = keeping the fluid from coming and spraying all over, when you bleed the air out.
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i have seen one better "fluid filler tool" out there. it might be common thing folks are buying now.
the standard remove the core of the tire nipple. then screw in the fluid tool. the fluid tool has a longer pipe that sticks up into the tire to bleed out air. and then around this longer tube. fluid comes in. ""kinda 1 pipe inside of another pipe thing"". so you can fill tire with fluid at same time you bleed the air out. going through the same tire nipple. and you just run the bleeder air hose back to container you are pumping from. so end of hose hangs above the fluid surface. so you pretty much attach and forget for a few minutes. and never needing to bleed air / turn on/off pump.
p.s. i think there was an on/off valve for the fluid hose. so you could back the off the fluid. and give the air a chance to escape the closer tire got to being 75% or so filled.