see this link for a pic
http://forum.koimag.co.uk/tm.asp?m=361193
The retro drain is attached to your pump and the water is sucked from the bottom of the pond drawing in the muck as opposed to a pump alone which will suck water from all directions. These are as close as you can get to a true bottom drain
http://forum.koimag.co.uk/tm.asp?m=361193
The retro drain is attached to your pump and the water is sucked from the bottom of the pond drawing in the muck as opposed to a pump alone which will suck water from all directions. These are as close as you can get to a true bottom drain