View Full Version : Herbie method on a HOB overflow

06/18/2010, 08:42 AM
Has anyone used this with a hob overflow that has two drains? One drain can be fine tuned and the other used for a back up.

06/18/2010, 10:32 AM
People have tried. There can be problems. The siphon from the main tank to the over flow can be slow and over flow. Imagine the main drain get blocked. The level in the overflow rises so the difference in height of the tank and overflow get less. So the tank drains slower. Emergency kick in at some point. But if the water height from the tank to overflow level does not support a siphon at a fast rate then the tank is filling. The tank will overflow even though the HOB does not.

I am not saying it can't be done, just something to check. In theory is should work, but you may need a deeper than normal box in the tank to keep the height difference.

06/18/2010, 09:48 PM
I did it and had no problems. I had to make a new box for the back side for it to work though. It had 3 chambers, 2 bulkheads.