How many gph for 2 1" overflow drains?

[desertfish]

gkrane, I have 2 1" holes drilled in the back of my 80 gal, about 3 inches from the top of the tank, with 6"Hx5"Dx7"L skimmer boxes glued over the bulkheads. I'm using 1 1/2" flexable PVC pipe plumbed to the sump. I have a Magdrive18 pumping the water from the sump back to the tank via 1" pipe. I figured about 9 feet of headlose on my return pump, that breaks down to about 425 gph per return (two returns). So I figure I'm getting 425 gph per overflow. If your tank is drilled from the bottom I'm sure you'll get a higher gph rating.
David

 

[twarren]

When I tried two pumps with 1000 GPH ( after head Loss Calculation ) returns from the sump on my 125 AGA tank the tank would overflow after a couple of minutes. A safe bet would less than 1000 GPH per overflow.

 

[gkrane]

How many gph do i need for a return on 2 !' overflow drains? I know i have to calculate for head loss, but what is the gph of drainage for each 1" drain?

 

[Seize-Er]

I believe a 1" hole is good for up to ~600 gph each.

keith

 

[ZeroMaintenance]

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Seize-Er I believe a 1" hole is good for up to ~600 gph each.
keith <HR></BLOCKQUOTE>

I agree, I have a 180 with 2 corner boxes and 2 1". My pump does about 1100GPH after head loss and it keeps my corner boxes busy not much more and it would be a mess. The biggest limiting factor for most people ususally is noise. The more watter you try to put into the hole the louder it gets. If you have a sponge in there it tends to clog up when you max out the hole. I almost had a big mess from that 2 weeks ago.