pump to overflow ratio ?

[roricaja]

I know there are a hundred posts on sumps but i have yet to find one that specifically answers my concern. I have a 125 gal tank. I intend on setting up a sump. i have found a overflow box rated for 700 gph. i intend to buy a Eheim sub. return pump. if i buy the 1260 which is rated for 635 gph, will i be ok? if i put valves in line of the overflow and one on the output of the pump, i should be able to get equilibrium correct? Please let me know if i need a smaller overflow or bigger return pump. Thanks in advance.

 

[roricaja]

the one thread i read said that the guy should have a pump rated lower than his overflow. that doesnt seem to make alot of sense.

 

[fsn77]

The key is to not have a pump that, with head loss, exceeds the maximum flow rate of your overflow. For example, if your overflow is rated for 700 gph, you would want a pump that can return the water to your tank at a rate in the 650 - 675 gph range (after head loss is factored in). Your overflow will only drain water to your sump as quickly as your return pump can put it back into your tank. There's a head loss calculator link on the home page that should be able to help you calculate the actual gph of your return pump after factoring in head loss.

If your return pump's gph after factoring in head loss is greater than your overflow's gph rating, you will be pumping water back into your main tank faster than it can drain into your sump. That means you'll flood your tank (and floor) and face the possiblity of pumping your sump dry.

 

[exacta123]

you never want to restrict the water flow comming out of your overflow into your sump

 

[Pete1399]

Use the head loss calculator on the home page and match up the brand pump you want with the total footage of return pipe (with 90s and such). Once you have done this your overflow and return will run properly.

 

[lvpd186]

I agree with fsn77, you really want your pump to be a little less then your overflow (after head loss). If you think about it, your overflow will only go as fast as your return pump, but if your return pump is too strong you can have problems. That being said it should be pointed out that if you want a bigger pump you can, you just need to make some adjustments. Like having it branch off through a gate valve to either something like a canister filter or whatever.