I am sorry but a picture of your overflow system would help me greatly.
Note:
If your system is new I would recommend start over. Drill your tank!!! Remove HOT overflow. I have one and it sucks.
All overflows
cannot be trusted.
A backup if you will...
Make sure the area where your return pump is will run out of water before your tank overflows. You may burn up a pump but you will not have to replace your floor. Add a baffel to your sump to ensure your return area is not attached to your main sump. I am glad I designed mine that way. (thanks Otty). My ATO will keep supplying water but...my ATO will run out of water.
Look into a desing for your overflow water/air pump so it pumps to an open area before it reaches your pump. Removes all the crap before reaching your pump. Something like: CD-18881 from the previous link I sent. This one is an air protection but one for sediment is good too. (sorry no pic there)
Zak