Megaflow Overflow problems

I have recently set up my aquarium with the megaflow overflow system down to the sump and the overflow will be running with the pump on but the overflow will drain to a low level, then stop and fill up to a higher level and drain again. I'v read somewhere before this might be caused by the air "vent" in the top of the drain. Does anyone have any experience with this issue? Is it easy enough to just make this vent larger?

Also, the volume of noise of water going into the sump is very loud. Can this be caused by this issue, or is there something else that can be done to help with this. The tube going from the bulkhead to the sump goes in a horizontal "S" shape, does this effect the flow as well? If i shorten the tube and put it directly under the drain will it help with either issue?

 

I think you are plugged up

 

If the vent hole is not big enough then you will pull siphon and drain the OF then it will fill up and do the same thing. Drill the hole bigger but go in increments.

 

I found some info here
MegaFlow overflow question

They say to limit the pump, I have a ball valve after the pump, should I close that a small amount? The pump may be pumping too much water up and into the tank causing the surge.

 

What size is your tank and pump? I have a Mag 9.5 on my 90g. The previous owner had a straw comming out of the vent. I took that off with no problems. Increased air a bit and my drain is much quieter. Plugging the air vent will make it surge from siphoning.

I don't know, but it seems you would need a much bigger pump to out do the overflow. Not sure if you have the drain at the proper height. Mine is set a little lower. An inch, from tank level.

 

I have a 65 gallon {36x24x18}. I cut the pipe to the size they suggested in the manual. I am going to try reducing the flow with the ball valve I have when i get home from work. I would make sence that if the pump is running at 800gph and the overflow can only do 600gph then I would have a problem.

If thats not the solution I will try drilling the hole a tiny amount larger.

 

My 9.5 will do 800gph, but with 4 feet of head, is only doing about 500gph with the associated plumbing. My vent hole is probably 3/16-1/4 inch.

 

Make the hole bigger on top or just take the top cap off and see if it surges. If it doesn't then that means you need more air to help with the flow.

 

Hello, yes! You are exactly correct. I had the same problem and I did open the air vent hole to the next size up and then changed my pump (I was going to anyway) and once I got the proper match up of pump gph and over flow gph it was fine. One more thing, try to get the flex tubing to form a "U" shape and play with that to fine tune if needed. So, the ball valve should do the trick.

 

I'm still curious what pump it is and if he is going by unrestricted flow rating, or factoring in plumbing and head.