over flow how to make it work.

[reefcrazy]

ok i bought a over flow at lfs and when i got home it didn't have instructions. i called lfs and they told me it was rated at 500gph. i bought a mag7 that pumps water up 4 1/2 feet up, that would be like 450 gph. i get the pump going but over doesn't work. any suggestions also the u tube on my over flow is 1in.

 

[wickedwes]

If you are just asking how to get the water to move from the overflow box, up & through the "u" tubes and down to the sump (basically just starting the syphon) then take some airline tubing and put it inside one side of the "u" tube until it is at the middle of the bend. make sure that you have a couple of feet of airling tubing. next put the "u"tube in position. next just suck on the other end of the tube to remove the air. Hold your tongue on the end of the airling tubing until you remove the other end from the u tube. the syphon should now be started.
Do not do this unless the overflow box is installed already. If you have questions regarding installing the oveflow box then respond back.

 

[johnnysalt]

A "less salty tasting" way of doing this is to connect the other end of the airline tubing to a nearby powerhead (with a venturi) instead of your mouth!

Again, another idea I wish I came up with on my own!
Another PLUS with this setup is that if (and WHEN!) your power goes out and your siphon stops....if you have an overflow box that does NOT hold the siphon, then:
1. the ph comes back on
2. it sucks air out of the box
3. that creates the siphon again
4. return pump is not burned up!
HTH,

 

[broomer5]

What would happen if you've lost power, lost siphon, you regain power, the powerhead fails to restart but the return pump does start up at power up.
Messy I bet.
LifeReef external overflows, or any properly designed external overflow - will not lose siphon if you have enough selected the right return pump, provide for enough water flow to force out entrapped air bubbles, and do lift the U tube.