Ok, here is what I am working on ...

RO/DI has a pressure type auto shutoff solenoid (non-electric). If the RO/DI water output is restricted (float valve, ball valve, whatever) presure builds up on the output side of the RO/DI and shuts off the input side. However, I think these pressure type shutoff solenoids are only good for 90gpd and less?

My RO/DI output goes to multiple sources (e.g. water change barrels), but all but the topoff are usually closed off with a simple ball valve.

I have a Reef Fanatic Level controller which switches on a 110v plug when the water is low.

I will be conecting an electric solenoid (normally closed) to the output side of the RO/DI with the solenoid plugged into the topoff controller.

When the controller senses that water is needed for topoff, the elecric solenoid will open releasing pressure on the RO/DI output side, which will release the pressure solenoid and input to the RO/DI will open. When the water level is back to normal, the controller will close the electric solenoid, causing pressure in the RO/DI output line and thus shutting off the input side to the RO/DI.

Now, a little more complexity. The output from the RO/DI will feed the input side of a sealed Kalk Reactor. Water flow into the Kalk reactor will force water through and out the reactor to top off the tank. With a DPDT relay, Kalk mixing will be turned on, via a small powerhead on the kalk reactor, whenever the electric solenoid is off/closed.

I am going to have Pete build the Kalk Reactor big enough for my system.

Make sense???

You are welcome to come se it once I get it all working.