overflow question

[sphelps]

yes I have. Comparing a standard standpipe to a Herbie with the same bulkhead size the Herbie will typically flow more. For example if your overflow is about 2 feet tall and you run a Herbie you have 2 feet of head pressure on top of your drain input to help push more flow in. With a standpipe you don't have this. Just like running a pump at zero head compared to 2 feet of head, but it works in an opposite fashion with a drain, more head pressure will mean more flow.

Of course I say typically because for this to work you have to have the primary drain located at the bottom of the overflow and not have any kind of extension tube, otherwise you don't have the head pressure to push more flow. To demonstrate try an experiment, fill an old tall container will water and punch a small hole in the side near the bottom and you'll see a jet of water spray out. You'll notice as the water level decreases, which reduces the pressure at the hole, the water jet will not spray as far.

You can also note that the primary reasoning for a Herbie is noise reduction not increased flow. The idea is the system can take a large amount of flow and drain it whisper quiet.