overflow surging

Just finished upgrading from a 75G to a 90G tank with overflow and sump. My over flow surges it will be flowing smoothly and then there will be a big surge of waterto my sump then return back to normal. I have tried adjusting the return and the overflow with little change.

Any suggestions please and thank you.

 

every few seconds?? sounds like its creating a back syphon and having to burp itself. Is the overflow tube sealed? a pic would help alot

 

What size PVC and how many GPH are you pumping through it?

 

Nice thought, over powering the overflow????

 

Same exact thing happened to me when I was testing overflows. I was trying to push 500gph through 3/4in PVC.... FAIL

 

Thats why my DIY intank overflow (surface skimming) with DIY HOB overflow is an inch and a halg PVC.
I think it's true you don't want to go too big or bubbles can stay trapped in the upper loop, eventually potentially leding to a siphon break.

NOw that I moved my sump from my stand to my basement, I"m contemplating gong back to a one inch overflow.

** OH, btw, when you said adjusting the return, I hope you werent limiting it with a valve, that can lead to a DT overflow FWIW

 

You have to much flow going down the drain. dial back the return pump a bit. should slove your problem.

 

+1 to this. I had the same issue using a eheim pump that was too many GPH. It was creating a surge and flush type of noise.

I dialed it back with an adjustable flow pump and it totally solved the issue.

 

The initial overflow is 1.5 in. the down to 1 in. PVC, the return pump is a maxi jet. With a 4 ft head it pumps at 600 gph but i am reducing that number with a return. It seems to surge every 20 sec like its not getting enough air to flow properly. I will take some pics today and post them, in the mean time heading to Big Als to see how there sumps run.

 

Thanks for the replies, after a lot of tweaking with flow i have got things stabilized all seams to be working fine. Maybe i will get some sleep, not getting up in the middle of the night to see if my tank is overflowing.