How do you prevent backflow?

So I just installed a CS90 Siphon Overflow with a RIO 1700 return pump. The issue is when power is lost the return U tube creates a siphon and will flood the sump pretty quickly. How can you prevent this from occuring? Basicaly the Rio 1700 has a 5/8" tube (3.5 ft) and then into the return u tube and into the tank.

I appreciate any advice

 

are you sure it's the u tube and not your returns siphoning? if it is the u tube then you could run your sump level lower,adjust overflow box height or you need a bigger sump.

 

Do you have syphon breaks on your return lines??

 

It is definately the return that is siphoning. I cannot fit a larger sump under the stand, 5.5 is the largest that can fit.

 

How do the siphon breaks work? No I do not have these in place currently.

 

A siphon break is just a hole in the return that allow air to ''break" the siphon.
I hope that helps i can't really think of another way to put it

 

Wouldn't water shoot out if you made a hole in the return tube? I am assuming it would be above the water line?

 

design your sump to accept the power outage situation or change the way its setup to allow oxygen to break the siphon

 

Yes it will but the hole is small and the water will go into the dt.