Difference between 1.5" and 2" drain in overflow

[sphelps]

Originally Posted by christyf5

So I'm at a bit of a loss with the photo you posted of the single herbie. Why does it have 1.25" pipe in it? Does the 1.25" pipe go all the way through, how is it affixed in the 2" pipe? And whats going on with the gate valve?

The 1.25" pipe goes all the way through (it's one piece) and acts as the secondary or back up drain. It's supported inside the 2" pipe by the bushing.

The primary drain is created by the 2" pipe. Water flows in between the 2" and 1.25" pipe and then through the gate valve. The gate valve is used to match the flow rate to the return pump and adjust the water level in the overflow box to just below the top of the 1.25" pipe. It's just like a standard herbie but the back up drain is inside the primary.

Make sense?