Hmmm my post disappeared.... well like I said it does the exact opposite the water level in the overflow drops then it starts to suck air and gurgle makes a hell of a noise I'll try to get a vid

I believe will do that because you have the pipe sumberged under water cause back pressure......so that when you plug that hole is cause's a syphon which pulls all the water it can from the overflow un till it sucks air!!!!

http://media.putfile.com/100-1336


http://media.putfile.com/100-1338


http://media.putfile.com/100-1339

http://media.putfile.com/100-1340






If I do that then I have splashing at the bottom and sucking at the top.....really starting to think this whole sump thing is a friggin pain.....Shoulda listened to Bev and Bob http://www.smilieshq.com/smilies/mad0235.gif

Have you tried moving the air hose up and down?

Spend $15 on a durso?

You pretty much have a Durso already and looks like setup okay as water level seems steady without the air-hole blocked. No sure how much difference replacing the one elbow to a Tee and cap (for a classic Durso) would make but all I know is when they are tuned, the drain pipe itself is quiet.

If the noise that causing the problem is the water fall effect into the overflow compartment, increase the height of the vertical pipe so the water level is higher in the overflow (less drop, less noise).

Difference on mine, between overflow compartment level and tank level is about an inch. As long as the overflow level is less than the tank (even 1/4") functionally it's correct.

Nobody has asked yet, how many gallons per hour are you putting through this overflow? How big is the bulkhead?

The water level looks a little high from the videos, I think the air hole should be slightly smaller, my water level is just above the half-way point of the horizontal PVC.

How does your drain line enter your sump?

Here are the mods I did to my DIY Durso to fix both the varying flow issue and the snail issue...

http://smg.photobucket.com/albums/v6...Anch=imgAnch11

http://smg.photobucket.com/albums/v6...Anch=imgAnch13

http://smg.photobucket.com/albums/v6...Anch=imgAnch14

A John Guest valve on some 1/4" line to control the air flow, and a slotted piece of PVC to keep the snails out.

I will try adding an air valve and a DIY snail guard looks like a good idear

The bulkheads are 1" the pump is a mag 9.5 950GPH with about a 4' head so idunno about 800ish GPH

How many 1" bulkheads are draining?

Have you tried throttling back the pump to see what happens?