More complexity, but couldn't you just use a small pump, and a float switch? As long as the feed line goes up before it goes down you avoid an accidental gravity feed, and if the end of the feed line doesn't sit in the sump water you avoid an accidental siphon feed.
both of you are right, but the problems that Im running into is this.
one tank is 400 gallons and the other is 200 gallons, so I dont think an aqualifter could keep up, maybe wrong though. Also, the sumps are about 4 inches off the floor, and the freshwater storage is in the same room several feet higher than the sumps. Actually it is on a stand almost touching the ceiling (about 10 feet) to save on floor space. Not sure I would have enough room to put a siphon break.
use the float valve and have the feed line higher in the storage tank. put in a powerhead or something else to agitate the feed water if you worry about something settling or getting stagnant. even if the valve sticks (mine never has in 3 years) you'll only get the top off water to the output line level, and then only what the RO/DI system can make. You could still have issues, but it would be a lot better than your entire tank of RO/DI water emptying in to your system.
<a href=showthread.php?s=&postid=12851100#post12851100 target=_blank>Originally posted</a> by areze I dont see the difference between a float valve operating a pump, or operating a valve... if it gets stuck open, the pump will pump it dry just as fast as a syphon...
either way your trusting the float valve. im struggling with the same thing myself, trying to figure out how to get redundancy in the system.
Well, with the pump you're using a float switch, not a float valve, which IMO are more reliable. Float valves can leak, even if they are closed. Switches are either on or off, and they can be guarded from snails and such much easier than valves. Also, you should use 2 switches together: the regular switch and then a second switch above that that will turn the pump off if the level gets too high. Because the second switch is normally dry, the chances of it failing and/or getting fouled by a snail or something are very slim.