[ksreefbuilder]

Ok, I have what may be a dumb question, but this is driving me crazy. My new drilled 125 tank return pipe has the standard size little hole in the 90 elbow for air or whatever, but instead of it being on the top underside of the elbow, it is on the top side of the elbow pointing out into the tank, and is causing lots of noise and micro bubbles. My old tank had the same setup, but the drilled hole in the elbow pointed down back into the overflow and the new one points straight out into the tank... My question is can I just replace the elbow, and if so why is the hole so important in it?

[demonsquirt]

Is the water level toped off? This hole should be about 1 1/2 inches below the surface. This hole is for preventing a back flow and flood by stopping the siphon in the event of a power outtage.

[ksreefbuilder]

Yes, the water is right up to the top of the tank, but the overflow is about 2 inches lower than the tank level. I think I will just replace the elbow and redrill the hole below the water line.

[unclejed]

You have me confused, here is a shot of mine (corner overflow); If somehow yours is going in the tank? plug that hole and drill one in the top. It is there to allow air to sucked in as the gravity pulls the water down to the sump, by allowing air in the water flows smoothly. If you didn't have the air hole you get a flushing effect like when you flush the toilet.

[ksreefbuilder]

Originally Posted by unclejed

You have me confused, here is a shot of mine (corner overflow); If somehow yours is going in the tank? plug that hole and drill one in the top. It is there to allow air to sucked in as the gravity pulls the water down to the sump, by allowing air in the water flows smoothly. If you didn't have the air hole you get a flushing effect like when you flush the toilet.

I am talking about my return pipe, not the overflow pipe. My overflow pipe is the new design and makes no noise at all.

[unclejed]

Sorry, when you said pipe, I have tubing from my pump (in sump) and connects to the 2 outlets which are under water in the main tank. There is no noise. Am I correct in assuming now that your return doesn't have nozzles? The water is shooting into the tank above the water line and mimicking a HOB filter?

[holiday]

I got a new 75 gallon about 2 months ago and the noise was driving me crazy as well. My 55 does have a hole but in a different spot. I put a piece of aquarium tubing in it and had it pointing into the tank. It fell out after 2 days of the water pressure. We switched to a hard plastic tube 2 inches long and the noise is gone and it hasn't fallen out. We thought the new design of the hole was so that it would help blow the top of the water around and have more oxygen and less skim on top.

Good luck, Noel

[ksreefbuilder]

I bought a new elbow today, and just drilled the new hole below my water line and it is working great. I think that is all I needed. Thanks for all the help guys

[Arnold40]

The hole is an anti-siphon. Do you have a check valve in the return line? If you don't have a check valve install one and plug the hole or replace the elbow.

[ksreefbuilder]

My under tank plumbing consists of only 2 pieces of 1” vinyl tubing. I have a gravity fed overflow line and the return line. My tank bulk heads came with hose fittings on them, and is a very simple setup. I think people over complicate the plumbing of tanks way too much. All I have ever used is vinyl tubing for plumbing my tanks.