Plumbing question: flow reduction via pipe size

[FlashJordan]

I'm in the process of a new 120g build, my first ground-up system, and in thinking about plumbing, I'm looking at external return pumps from my sump. My tank is 48x24x25, peninsula style with an 18" trapezoidal overflow on the one side. I have 1-1/2" Drain and a 3/4" return, which is proving to be an interesting combination.

Here's the issue: I want to have somewhere in the neighborhood of 1200gph turnover in the tank, but the pumps that I'm looking at (Iwaki MD40RLXT or maybe a Gen-X) have 1" outlets.

My question, I guess, has to do with what will happen if I reduced the outlet on the pump from 1" to 3/4"? Will it only reduce the flow rate, or will this be detrimental to the pump as well? Maybe I haven't looked hard enough for a pump that will fit, but I really like what I hear about Iwaki's and I'd like to make it work. Is there another option that I'm not looking at?

For what it's worth, I'm also considering a Durso standpipe for the drain, though I don't know this has any bearing on the situation, as their 1-1/2" drains are supposed to accommodate a 1200gph turnover.

Thanks, and happy Friday!

-J

 

[loscaer]

Reducing the pipe will just make your pump work harder, witch is fine. Get a pump that is over 1200 gph to make you get the turnover rate you want.

 

[sirreal63]

Forgetting the issue with downsizing the return, are you aware of what 1200 gph will be like flowing through the sump? That is a tremendous amount of water to move through the sump on a 4' tank, bubbles that will be created will not have a chance to dissipate, and debris that is sent to the overflow will not settle there, but instead be swept back to the display and the Durso will be very noisy. Most people shoot for 3 to 5 times the display size for flow through the sump, any more than that is just a waste of electricity and hampers the efficiency of the sump.

 

[FlashJordan]

Forgetting the issue with downsizing the return, are you aware of what 1200 gph will be like flowing through the sump? That is a tremendous amount of water to move through the sump on a 4' tank, bubbles that will be created will not have a chance to dissipate, and debris that is sent to the overflow will not settle there, but instead be swept back to the display and the Durso will be very noisy. Most people shoot for 3 to 5 times the display size for flow through the sump, any more than that is just a waste of electricity and hampers the efficiency of the sump.

Ah. I think I see where I was misunderstood. I guess there are different calculations for flow through the sump and flow in the tank. I think the 1200gph I was getting was for the tank.

So, now I've heard 10-30x in the display, and 3-5x for the sump. Is this correct?

That may solve the connection issue as well, thanks!

 

[billdogg]

the general rule of thumb for sump flow is to match the turnover rate to whatever your skimmer can handle. You will be better served by increasing flow in the DT by using well placed powerheads.