<a href=showthread.php?s=&postid=6253097#post6253097 target=_blank>Originally posted</a> by calvin415
Exactly! The switch is for running an electric top off, which to me means that it's guaranteed to fail.
I prefer the gravity fed/mechanical method.
Okay, so I had a really long post typed up and then my computer crashed. These work computers really suck (and if anyone from my IT department is reading this, I'm sure you'll agree

). Anyhow, I'm going to now paraphrase what I typed...
I can hook up multiple float switches in series which requires that ALL switches (2, 3, 7, 29, etc...) fail before my ATO pumps too much fresh water into my system.
Gravity does NOT fail, therefore, gravity fed systems have a higher likelyhood of adding too much fresh water.
Basically, I agree that a float switch is more likely to fail, but it is much harder to add redundancy to a float valve system as opposed to a float switch system.
I guess another way to say it is, if (when) a float switch system fails, the system will be under-topped-off (must be manually to topped-off). If a gravity-fed float valve system fails, it will empty your water resivour, lowering the SG/salinity of the entire system.
Just my 2Ã"šÃ‚¢.
-Scott