please help me understand plumbing

[Reef-Geek]

Hi, I bought the aqueon plumbing kit and the return pipe makes random air bubbles, I think I can solve the problem in 2 ways
1. turn the return valve half way, I am using eheim 1262 which maybe too strong for the 72 gal but turn it half way is just reduce too much flow
2. like the picture shows, there is a hole as marked, if I use finger to cover the hole the bubble's gone, what is that hole for? is it needed?
http://i43.tinypic.com/351wr37.jpg
so what can I do to reduce the bubbles? thanks
ps. the I don't think they are microbubles.

[Cal_stir]

the hole is the break the siphon if the pump stops and reduces the amount of drain back to the sump, the hole is usually just below the water level, sounds like you are getting a venturi effect drawing air into the pipe

[coolhandgoose]

The hole is there to act as a siphon break. If you didn't have it and turned off your return pump, your display tank will start to drain into your sump via the return line. Not sure why it would be producing bubbles, is it underwater? How deep is it?

[Reef-Geek]

the hole is the break the siphon if the pump stops and reduces the amount of drain back to the sump, the hole is usually just below the water level, sounds like you are getting a venturi effect drawing air into the pipe

no wonder, it should be below the water level

http://i43.tinypic.com/35hfsqe.jpg

what should I do to fix it? I can raise the water level in overflow by adjust the drain pipe's height, but I cannot raise it too much...

[Cal_stir]

if you can remove the pipe you could plug the hole with epoxy and drill a new hole a little lower
if you can't remove the pipe you might be able to drill a new hole, make sure u use a cordless drill and underwater epoxy

[coolhandgoose]

You could plug that hole and make like a U shape with plumbing so the U saddles over the overflow box, then drill a hole just below the water line on the display tank side. Hopefully that makes sense.

[coolhandgoose]

Cals idea is probably easier :lol:

[Bblinks]

Plug it up or wrap some teflon around the joint.

[Reef-Geek]

thanks guys, if I stick in a small piece of air hose and submerge the hose in the water, will it work?

[Cal_stir]

yep

[Reef-Geek]

yep

thanks, but the problem is why they make it this way, obviously the hole won't below the water line, did they do it on purpose?

[Cal_stir]

i don't think they made it that way on purpose, maybe your overflow is a little short or the fittings didn't push all the way in when glued, or some other glitch but i think the hole should be just below the water