Automatic top-off
Automatic top-off
I'm not sure if it's a temporary or permanent special, but my system included an ATO that was backlogged and just arrived.
The ATO includes the mount and the switch - the water is up to you.
The hose connection is a little unusual - a plastic compression fitting. Just push the hose straight through the nut so that it sticks out the back a little, and then screw the nut on.
To install the ATO correctly, you need to have 1/8" hose and a water source with the hose running down in to it.
Consider the volume of your freshwater reservoir. ATOs are notorious for getting stuck in the ON position. Giant snail crawls onto float and weights it down, salt creep, hinge pinches your gem tang's head... So it is probably safer to assume that the whole reservoir will be released at once some day. If you keep the volume less than the air space in the sump, then you won't get a flood or reduce salinity so much that your livestock suffers.
If you want to plumb ATO directly to an RO, I don't think this swithc was made for that kind of pressure. In any case you should have a secondary safety system to keep a stuck switch from pumping 50 gallons of fresh water into your 39g tank. Plenty of options described elsewhere in ReefCentral.
Install mount, connect water, run return pump into a bucket until you find it sucking air. Set float level and let it run until level comes back up and that ATO shuts off at the right point. Repeat as needed. If you already have life in your tank, make sure to do this experiment with a saltwater supply rather than fresh.
If you set the hose to siphon, you'll need to prime the siphon.
Install the ATO in the front of the pump chamber - that is where the level changes when water evaporates from the system.
Figure out where the pump starts sucking air - you want the ATO
to kick in just before the level drops to there. So slide the float switch along the mount until the flow starts there.