//Mods please feel free to move this to the appropriate sub-forum, if "project guidance" is not correct.
So I have a gravity fed humidifier. I tapped into the 1/4" Ice Maker water line and created a simple circuit with a flow meter and solenoid valve to automatically refill the tank. That all works great when the tank isn't installed onto the unit (tank is removable for refilling using regular tap).
JUST ONE LITTLE PROBLEM: the tank feeds/operates on a vacuum/gravity principle. Normally the tank maintains a vacuum, and only allows water to flow when the level gets low enough in the water reservoir underneath the tank that air is allowed to backflow into the tank, releasing some of the pressure and allowing the humidifier to feed.
To accommodate automatic refilling, I drilled a hole in the tank to feed my 1/4" line in, as well as two vent holes at the top.
THAT WAS A BAD IDEA.
As soon as there is no vacuum the tank will flood the humidifier reservoir. So the tank must maintain a vacuum at all times to avoid this problem. So I tried adding one way check valves and sealing the tank again. That stopped the humidifier from flooding. Then I realized that even if I release the pressure and maintain a vacuum while filling using one way check valves, because the tank's valve at the bottom is open while the tank is installed in the unit, water will just run out and overflow anyways, and the water level in the tank will never rise to full, instead it will just overflow.
Cap with valve automatically opens when placed onto unit, allowing water to feed from tank into reservoir well during normal operation:
So now I need to seal off the tank from the rest of the unit while refilling.
Whatever I do, it's going to have to be done inside the tank itself. I am thinking of sealing off the tanks feed valve at the bottom and then using a float valve that would cut off the flow from the tank to the reservoir when the water level in the tank gets low, and only open it again when the tank's water level is topped off. That seems to be the easiest solution.