Auto Top Off
Not to dissapoint, here are the details of my auto top off system:
The first problem to overcome when using an RODI unit in an auto-top off system is that an RODI unit is not electronic in any way. There is a hydraulic way to control an RODI unit, with the use of a float VALVE, and a hydraulic valve. When the float valve in your water container or tank closes, pressure builds up in the line, the hydraulic valve closes, and this shuts off production of both waste and good water from the RODI. the hydraulic valve is spliced into the plumbing of the RODI unit with quick disconnects. This system is commonly used for RO drinking water units. The problem with using it for a reef though, is that the line between the storage container and RODI can be quite long, and not enough pressure builds up to trigger the hydraulic valve consistantly. No flooding happens, but your RODI unit keeps pumping out waste water forever, no good. You can solve this by installing a bladder right after the RODI unit to build up the required pressure.
BUT, there is an alternative way that I prefer, or even better, use both systems for redundancy. Everyone knows what a float switch is, it turns on and off with changing water levels. I setup 4 float switches for redundancy purposes. This goes to a 12v relay switch (to limit the voltage to the switches or they will blow) which is connected to a sprinkler solenoid. The sprinkler solenoid is perfect because it attaches to your water system in the house, same as your RODI unit does. So, when the float switches call for water, the sprinkler solenoid opens, and allows water to go to the RODI. The RODI then fills the resevoir or your sump, the float switches turn off, sprinkler solenoid closes, and no more water to your RODI. The sprinkler solenoid also defaults to OFF without any power, so if your power goes out, no worries of a flood. 4 float switches are not necessary, 2 is probably good enough, one higher than the other so that if one gets stuck, the other is a backup. Mine are setup so that they are in pairs, and one from each pair has to be activated, or the relay and sprinkler solenoid do not get triggered. This protects me against multiple failures in the on or off position.
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