osmollator pumping in reverse

[JohnSiesta]

Just hooked up my Tunze Osmollator top-off last night and ran it for a day. It seemed to work fine. I added 1o gallons to the sump-refuge up to the top range of the top-off and went out to a meeting. I came back 2 hours later to see that the pump had gone in reverse (if that's possible?) and pumped 5+ gallons back into the freshwater resevoir and that had then spilled all over the floor.
Any feedback on how this happened and how I can avoid it in the future?

 

[Phyxius]

I`m sure Roger will be along to help shortly. The pump running in reverse I think could only do that if you have the outlet tube(top off water coming out) actually under water in your sump/tank where you have it mounted to. It would need to be able to pull the water out of the sump or tank and would have to be under water on the other end to do that.
It should also have a the anti-back flow valve included installed in line to help prevent that scenario. Is your top off container below the level of your sump/fuge area?

I have 2 of these set up on 2 tanks and never had a back flow problem. My top off ends are above water level in the tank and higher then the top off container.

 

[rvitko]

It likely siphoned the water out, the hose cannot touch the surface of the water or this will happen. I have never seen a pump run in reverse.