Bad experience so far today

lol thats totally understandable and makes good sense. I hate hearing about this stuff happening to other reefers

 

I think I get what your saying. You were relying on a check valve rather than space in your sump in the event of the return shutting off. the pump stopped and the check valve failed making your sump overflow more water from your system than your ato holds. when the return pump kicked back on the ato drained trying to fill what was lost in the overflow. The ato didn't hold enough water so the return ran dry.

Are your sure you didn't have a power outtage?

 

That's what I think basically happened, except that the DT tank never overflow. I think the pump while still on, stopped pumping, resulting in water coming from the DT to the sump through the return. The check valve didn't work, and while there was some room in the sump for extra water, there was too much. The sump overflowed, causing the skimmer to overflow. Then the return pump started pumping again at some point, this stopped the water overflowing the sump, but b/c the water overflowed the sump there was too much gone for the ATO to replenish causing the pump to run dry, the ATO to run dry and my skimmer to overflow. If you can understand that, K+. This is the only scenario I can think of that would have caused everything to have happened the way it did. You guys have come up with some good alternate ideas, but the facts and my setup can prove them wrong.

 

To remedy this, I have already drilled a small hole in the return nozzle just below the water line to the DT to act as a siphon break, so at least the sump won't overflow again.

 

Could have been worse I guess...looks like you got a good size sump, why do you need a check valve on your return pump? The overflow and sump should have been designed to handle whatever overflows from the DT should the return go out, without the need of check valves....this is the main reason I don't like the check-valve idea, you have to constantly clean them or this is the result. you drilling a small hole in the return line just below the water line was a good idea, just make sure it doesn't get clogged up....you might want to drill 2 holes. Does that mean you could remove the check-valve now?

 

It was designed to hold all of the excess water and did before. But about a week ago, I cleaned the pump and when I put it back, the return nozzle dipped lower at an angle, effectively allowing more water to siphon back, I didn't think much of it at the time, but now know better.

 

Well the good news is that my sump wasn't leaking. I've had it back up and running for the past day, no problems so far. I pretty what I described earlier was what happened, as I can't think of any other explanation. What I'm surprised at is that the return pump was operating dry for a couple of hours, and it still works. Thanks for all of your input.