Necsones

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Yonkers, NY
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how do you know what your overflow box can handle? I want to get a new return pump and thinking about the Mag Drive ones. I have about 4 feet of head so would a mag Drive 9.5 be to much? i have a 55 gallon tank.
 

BZOFIQ

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overflow boxes are know to fail and then you flod the floors with whatever you have in your refugium. Not recommended. General consesus is that 1" bulkhead can handle up to 600 GPH.
 

KathyC

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Barnum Island
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If it has a single 1" hole at the bottom, it will move 600gph. A Mag 9.5 should be fine as over time it will pump a lower amount of water due to build up within the piping. Remember that you want to put a gate valve (way easier to adjust than a ball valve) on the OUTPUT side of the pump, so that you can balance the flow between your OFB and your return ..and do add some Unions so that it if you have to change the pump at some point or disconnect something, your life will be waaaay easier :)

btw for the naysayers....I have been running an OFB on one of my tanks for a couple of years now and have never had an issue -if it is installed properly and has a siphon break. It is NO LESS RELIABLE than my RR tank.
 

Necsones

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Yonkers, NY
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so i did some searching around and think im going to go with the Mag Drive 7.. with the head loss it should pump about 420 - 500 gph. i read some where that the slower the movement in the sump/fuge is good for the skimmer to work with the water alot better.

Think thats a good idea??
 

KathyC

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Barnum Island
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so i did some searching around and think im going to go with the Mag Drive 7.. with the head loss it should pump about 420 - 500 gph. i read some where that the slower the movement in the sump/fuge is good for the skimmer to work with the water alot better.

Think thats a good idea??

Not necessarily. If you tank is draining at 600gph and you are only returning an average of 460gph to the display tank, you will be in trouble within the first few minutes and your sump will overflow.
To use a smaller return pump you'd need to reduce the size of the drain hole on the OFB.

A spihon break is usually 2 small holes (in case a snail is sitting over one of them or it gets clogged) drilled slightly below the water line in whatever contraption that will be on the end of your return line that puts the water back into the DT.
This will stop any water from draining from your DT back to the sump (and possibly overflowing it, which is the reason people freak over OFB's) if the pwer goes out on your return pump. Once the water level drops to the pount of the 2 holes NO water will continue back to your sump beacuse the siphon is broken..hence the name :)

Hope I explained that correctly!
I'm certain that if I didn't many people will jump on & say so!!
 

Keith P

Mr. No-Show
Location
Great Neck, NY
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Kathy are you sure? I thought it was UPTO 600gph. The siphon just goes over the tank, not all the way down to the sump. So it should only overflow as much as you pump into the DT.
 

Necsones

Experienced Reefer
Location
Yonkers, NY
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Kathy are you sure? I thought it was UPTO 600gph. The siphon just goes over the tank, not all the way down to the sump. So it should only overflow as much as you pump into the DT.
thats what i was thinking.. heres my ovb
MVC-012F-2.jpg
 

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