# PVC overflow problems



## HiReZ (Jul 19, 2011)

I am trying to setup a overflow for my 75g. its 1-1/4 in PVC. flow is good (keeps up with my return pump), but is gurgles and sucks air like crazy! I have looked at many similar projects on forums all indicate that this should work. I have sucked out the air from the top. I can shut off the return (simulate a power failure) and it drains down to the intake, and upon restart continues siphoning. although it does oscillate a bit; it will flow a bit more steady and full up my refugium about a half inch... then big gurgle and the pump will pull out about a half inch, then it stays about steady for a bit but with constant gurgling.

and thought on what i should change? pics attached.


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## Deeda (Oct 12, 2012)

The problem I see with your DIY PVC overflow is that the in-the-tank bottom 'U' is not even with the out-of the tank bottom 'U'. These two pieces must be the same length to function properly. Also, the tee that drains the water to the sump must be above the bottom 'U''s.

Check out THIS link, there is an animation at the bottom of post #2 that shows how the overflow is supposed to be made.


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## joescaper1 (Feb 14, 2013)

The fix is pretty easy. Just cut a section from the outside drop that will allow you to equalize the inside and outside lengths, then cement it back together with a coupling.

Joe


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## HiReZ (Jul 19, 2011)

Thanks for the info. I had not come across that site yet. though it is very similar to a youtube video i saw.

however, I had my original design based on this (outside and inside U tubes at same level) and I could never get it to flow. after a few hours of resetting and repriming and only getting a trickle out I gave up to go do some more research. That's when I came across this thread:http://forums.saltwaterfish.com/t/297623/pics-diy-pvc-overflow
the improved design has the outside tube LOWER than the inside tube. My understanding was that just like a lowering a siphon tube further below water level increases flow that is what lowering the outside down tube in the pvc overflow.

so I'll give it another go with your advice. perhaps should I make the inside U lower in the tank? and the outside loop even with that of course.


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