Sump Return Pump

I have a 36 gallon bowfront and i have decided to put in a 10 gallon sump. I have a 300 gph overflow box and am wondering what size return pump I should go with. I know that it has to be larger than 300 but I'm not sure HOW much larger. The pump will be around 4 ft below the top of my display tank and i plan on using 3/4" PVC. It's pretty much a straight shot to the top of my tank, only 1 or 2 slight turns. Any suggestions?

 

The pump actually needs to be less gph than the overflow, if it is more, it will pump all the water out of the sump and run dry.

 

I thought it had to be more to make up for the height. But i guess having less coming up is better anyhow. Thanks

 

With the height you will get less out of the pump. If you can figure out exactly how many gph you will get at 4', they you can get a bigger pump, as long as the gph going into your tank is less than your overflow. I wouldn't do that because I don't want to walk that line, you risk burning the pump and overflowing your sump. Basically, you need a net gph into your tank that is < 300gph.

 

The drain and return needs to match. Get an over-sized pump (not overkill, just account for loss of flow due to height) and dial down with a valve until everything flows smoothly. Look at a chart for the pump you plan to buy to match the drain of your tank at the right height.

If you buy too small the sump will fill too quickly and you'll need to get a new pump. If you go large you can adjust to the right amount of flow and everything will run smoothly.

 

Okay I'm looking at the Rio 1700. Base is 642 gph and it says at 4' it will pump 352 gph. The next step down pumps 243 gph at 4' so I think I'm just going to go with the 1700 and turn it down at little.

 

That's not entirely true, the sump will fill a little more, but it will find a balance. It's kind of hard to explain, but if the pump pumps 300 gph into the tank, then the overflow will only drain 300 gph, even if its an 800 gph overflow.

 

It's easy to explain..conservation of mass! In=Out