Herbie overflow tuning
 

So my new tank came with herbie overflow and I am having an extremely hard time to tune it to a constant level. No matter what, water level always goes down or goes up over hours. This is going to be a big pain with ATO.

So herbie overflow experts, please help :)

Are you using a ball or gate valve?
The key is making tiny adjustments and waiting 30min

Gate valve for the adjustment. So I adjust the valve and wait for 30mins and adjust accordingly? Do I have to do it everytime I turn on/off the return? And how often do I have to adjust it?

once you find the sweet spot it should be good. I find I need to open it fully once a month and flush it out.

Great; that's a relief :P Thanks for the info :)

I find when your sock filter starts to get dirty it ups the level in the overflow, change the sock for a clean one and it's all good. Agree with the sweet spot comment. Also make your adjustments small and like was mentioned wait 30 mins. to see where you end up.

Could you take a pic of it? It shouldn't be that hard to adjust. I'm wondering there is something odd about the way it is set up.

Do you have one or two overflows? If two, are they plumbed together with a single outlet to the sump?

http://i1304.photobucket.com/albums/...ps853b060c.jpg


Its just a single overflow.

Yah people do say filter socks sometimes cause more problem than good and so I decided to not use any socks. Will put some sponges between the baffles.

It's probably one of three things

1. Operator - improper adjustment, it can take a bit to find that sweet spot, you can sometimes adjust it close to the point walk away only to hear it slurping air a couple minutes later. Then you over compensate in the other direction, always missing the actual point.
   
2. Air draw - flow rate is too high for primary pipe in overflow height. The higher the flow rate and the smaller the pipe diameter the higher the intake velocity. The higher the intake velocity the more space you need from the top of primary pipe to operating water level in the overflow. If the space is inadequate you'll gnerate the occasion vortex with brings air into the line which messes up the flow rate.
   
3. Inconsistent return flow rate - a few things can cause this but your return pump has to pump a consistent flow rate. Obstructions at the pump intake, air bubbles, poor quality pump are all examples.