Auto Top Off

This is exactly the same design i decided to go for,  i think its much simpler than some out there but provides at least one level of redundancy for flooding which was a requirement.

I went one step further even and drilled and plumbed overflow lines from the very top edge of my sump down and to a floor drain.  this way if the sump ever gets up that high it will start autodraining.  yes this will lower the salinity over time i figured 1.5 days would lower it to a point where it would start becoming real trouble for tank inhabitants but it will prevent potentially 100+gpd of water ending up on my floor.  a small price to pay if you ask me.

the only downside to this system is something john pointed out, in theory r/o systems produce "better" water on their 10th+ cup than their 1st.  to test it out i  used my tds meter on the 1st cup as well as after letting 2 gallons come out.  both readings were well below safety margins and insignificant between the two.  so maybe in practice its not such a big deal....

I thought I was quite tricky about doing this =)

I ended up buying 4 1/2 inch bulkheads from erik at marine aquatics.  they are threaded so you can then go to home depot and get "rainbird" threaded to barbed connectors, and then put some 20 foot hoses and routed them behind the workbench to the nearest floor drain.  i even "tested" to make sure that they would flow faster than the autotop off and obviously it was no problem at all.  but a nerve racking "test" =p

i only used 2 of the bulkheads for the drain.  the other two i used for plumbing automatic water changes =)  so now i only have to add salt to a 30 gallon container once a week and i get automatic water changes as well!  now THAT is a pleasure...