over flow box questions

[vanillaprice]

I recently bought an overflow box used. I was told it was only 300 gph. It has a 1" drain on it. I have seen 600 gph boxes with only 1" drains. My question is what is the factor that makes it 300 vs. 600. Also what pump would you recomend for this size overflow box. This will be my first using one and I don't want water all over the place.

 

[fishfarmer]

What brand of overflow box is it?

 

[vanillaprice]

it does not have a name on it.

 

[fishfarmer]

Does it have u tubes or is it a square siphon with a little hole at the top of the siphon chamber?

Usually the flow rate is based on the size of the siphon tubes.

 

[vanillaprice]

It has a U tube. Both the U tube and the drain have a 1 1/4 inside diameter. Hope this helps

 

[fishfarmer]

Sounds like an Amiracle or Lifereef not a CPR overflow which I was fearing. I would get a pump that would push slightly more than 300 gph maybe a 400 gph, because you will probably lose some gph by pumping up from your sump to tank. Most pumps should have a flow rate vs. head chart listed on the box. You don't want to get a pump that will overwhelm the overflow, you will probably still have to install a ball valve from the pump to the tank to be able to regulate the flow so you don't run your sump dry. I've heard it's best not to valve back the flow more than 45% because of excessive wear to the pump.