[ryeguyy84]

Avast marine makes a normally closed solenoid valve that you plug into an apex outlet. from there you could use a float switch wired to the apex breakout box that would trigger the solenoid valve to open and fill your holding tank. I would use 3 float switches one for low level, one for filled level and one mounted slightly higher as an emergency shut off.

this way your RODI isn't filling small amounts so your DI resin will last longer and the emergency float will at least stop the flow if the high switch gets stuck.