How does a twin-stand pipe work?

[JonB]

I saw on this forum about this method in a weir and as im in the process of planning my tank. I saw this ://www.ultimatereef.net/forums/showthread.php?t=332069&page=2 about half way down there is a brief description and a pic but I dont get how this works?

If any one could explain that would be great and the benefits?

Thanks

Jon

 

[melosu58]

Moved to General Hardware and equipment discussion.