If you are running the herbie correctly you should have no bubbles.
1. to confirm there are two main drains? one one emergency? this is more like the Bean overflow if so. With a herbie there is usually only one main drain and one emergency. The main drain acts as a syphon via a gate valve. you close the valve until a full syphon is made. therefore there should be no bubbles.
The tank has 2 overflows, each with a main and an overflow. The mains are Teed and the gate follows that into the sump. The emergency's are each seperate.
2. the tee is before the gate valve?
Before
3. both main drains (if there is two) stand pipes are the same height in the weir? and both are reaching full syphon?
Yes to both. But... The one side has to have a larger dia drain beacuse that pipe is longer. Took me a while to balance both overflows to the same level, but for the most part, this is balanced.
4. is there any water going down your emergency drain(s)?
No
5. how far underwater in the sump are the main drain(s)? For best results it(they) should be about an inch under the water.
Its about an inch or so with a fresh sock, but increases about 8" during the socks 3 days in there. I believe this increase is where my main problem is.
6. there should be about six inches difference in the height of the main drains and the emergency drains. Main drains being lower of course! this will allow some fine tuning.
I'd say there is about 4". If the main was lower it would be harder for the bubbles to reach the inlet.
I have run filter socks with my herbie with no issues at all. To me it sounds like the main drains are not reaching full syphon.
The water level in the overflow is 3" over the drian inlet. There is no vortex sucking air or anything like that.
try closing the gate valve a little more. this will raise the water level in the weir and hopefully stop the bubbles from there too.
I'm an inch from the emergency as it is.
HTH!
cheers:beer: