View Full Version : dual 2 inch overflow: What return

11/10/2007, 12:24 PM
on my 90 gallon i have dual 2 inch over flows going in to s 30 gallon sump/refugium. and I am starting to think my little old mag 7 will not do the job.
what return pump do you think I should have. I need the pump to be quiet also and push a lot of water and the is easily to find here on the rc used.


11/10/2007, 12:34 PM
Mag7 is fine. I have found them to be on the noisy side, but if it is working OK, use it. Use 1" plumbing for the return.

11/10/2007, 12:50 PM
well the plumbing is already done and the mag 7 has a 3/4 inch outlet so i stuck with that.
isnt each 2 inch overflow 1200 gph of overflow so i will have 2400 gph and with the mag7 after head loss is going to be around 450-500 gph.

11/10/2007, 12:57 PM
You dont need to and dont want to match the overflows maximum capacity. 2400 GPH would be a terrible idea. Generally, 3 -5x display size from the return. 270 - 450 GPH in your case.

11/10/2007, 02:24 PM
I think a 2" bulkhead can do a lot more than 1200 gph. CPR's 1.5" overflow box is rated for 1600 gph.

Heck, I have a sequence barracuda hooked up to my oceanic 75 and that only has a 3/4" and 1" bulkhead, both used as drains. I added a 600 ph overflow box to feed the skimmer, but I'm probably doing 3000 gph in my setup.

2400 gph might not be too much for the overflows, but I think it might be a bit much for a 30 gallon sump (mine is 150 gallons :smokin: )


11/10/2007, 02:48 PM
well i tested it and had to cut the ball valve down to barely nothing

11/10/2007, 03:02 PM
You had to almost close the ball valve on a mag 24?

You have 2 2" overflows or 2 1" overflows? What size is the plumbing on the drains?


11/10/2007, 03:21 PM
2 2" overflows to 2" pvc pipe
Mag 7 3/4 inch pvc pip return

11/10/2007, 03:28 PM
Wow! So the system isn't even doing 500 gph or so? Where are the bulkhead fittings? On the back of the tank or in an overflow box?


11/10/2007, 03:31 PM
Post some pics or a diagram. A Mag7 can barely do 400 GPH with 3/4" plumbing.

11/10/2007, 07:19 PM
my 120 AGA has 2 1" overflows, and my Mag 12 can run wide open. I have the return setup expanded from 3/4" off the pump to 1 1/4" to a T after the T it goes down to 1" flex PVC to 3/4 inch returns. I have another T going back to the sump to control the flow.