Overflow issues

[wonderbassist]

I have a 125g display which I have drilled a 1in overflow into, my return pump can get 1350gph and at 30% (lowest setting) on a 3/4in pipe is too much for my overflow. I added a 75g sump recently so I would like to be using the return at higher speeds anyway. Will I need to drill another overflow to do this, or can I get more flow from the original? Tank is full so I’ll probably need to do a siphoned flow.

 

[T-J]

The maximum flow through 3/4" schedule 40 pipe (using gravity) is about 660gph. Here's a great chart that can help you decide how you want to proceed:

 

[DavidinGA]

Clarify...you have a drain with a single 1" pvc?

Your return line is 3/4"?

 

[wonderbassist]

Yes, single overflow with 1” pvc there are 4 elbows on that which I don’t think affects gravity drains. 3/4” pvc for the return with 7ft of head pressure

 

[T-J]

Yes, single overflow with 1” pvc there are 4 elbows on that which I don’t think affects gravity drains. 3/4” pvc for the return with 7ft of head pressure

Ok, so with 1" PVC, the max gravity rate would be just under 1000gph. The elbows do affect the drain rate, and will slow it down.

 

[DavidinGA]

Add a line off your return (use it for a reactor or something) to further reduce your return pumps gph rate accordingly til you get a balance that works for your drain.

 

[wonderbassist]

Ok, so with 1" PVC, the max gravity rate would be just under 1000gph. The elbows do affect the drain rate, and will slow it down.

If my pump is running at 30% that’s only 400gph, Do the elbows slow it that much?

 

[wonderbassist]

Add a line off your return (use it for a reactor or something) to further reduce your return pumps gph rate accordingly til you get a balance that works for your drain.

Smart, I still want higher turn over for my system volume but that will work until I can figure out another overflow!

 

[DavidinGA]

If my pump is running at 30% that’s only 400gph, Do the elbows slow it that much?

It should not slow it down that much.

Are you running only that one single 1" drain for your system? No secondary backup/emergency drain? You definitely need an emergency drain if you don't have one, or else your going to have a flood at some point!