Why is my overflow gargling???

Bump. Well I've tried everything you've said 2in10 but nothing seems to be working. If I calculated this correctly my return pump is pumping up somewhere around 100gph, less since I've been trying to cut it back to make it stop sucking in air, and my overflow is rated for 300gph. The instructions say to match the two as close as possible.

 

If you elbows in the over flow lines they may be the cause because they can back up the flow. Hopefully some else will have an idea.

 

yes match as close as you can and then do what I did
my return line is straight except for the over the tank edge

 

Alright, I'm working on making the drain line straight which is involving some carpentry work so I'll see how much that helps.

 

The drain line can have a couple slow bends in it; the return line is what needs to be a straight as possible....IME

 

I had the same problem. I could get it to stop by matching in/out as close as possible OR slowing the return down A LOT, so that it no longer need to suck, but could just easily flow into the hole. It's a balancing act. I also added a foam piece that the water can flow through at the bottom, it helps to dampen the sound and doesnt gurgle but its still a tad audible... I'm just playing with it until I get it right...

 

Well keep your fingers crossed this worked, I straightened out the drain line and return line and played with the return speed a little and it seems to be quiet for now.

 

I had this issue with my CPR as well, but I didn't have the sponges or hard tubes in the outlets (bought it used). I ended up taking the plastic screens out and built some durso stand pipes. Problem solved. If you play with various couplers and elbows in Home Depot (or the like), you can build one without the need for any cutting or glue. Just wrap some teflon tape on the male ends.

 

This problem is a very easy fix alot of times you just need to put a ball valve in the overflow pipe so you can adjust the overflow. It only takes a very very small adjustment of the valve and the flushing sound will go away. The adjustment is so small that it really dosnt affect your flow much at all. After you put that valve in you should be able to turn your return flow back up and adjust the overflow ball valve until the flushing goes away.

 

Ok, thanks for the info, I will definitely do that in the future. I've done enough work on my tank recently that my corals hate me right now so I'm going to let things calm down and return to normal for a while. I got it to quite gargling and sucking down huge air bubbles for now.