According to the "experts" you should have one 4" gravity fed drain every
10'. To work effectively, you should have a 1/2" drop per foot to the drain.
Don't forget the anti-vortex cover over the drain, or it will merely suck
the water from directly above instead of being forced to draw the water from
the bottom. 4" drains are preferred because they will not clog as readily,
and if an inquisitive fish *does* go down the drain, it has room to make it
to the settling tank on the other end without getting stuck. DIY types can
jerry-rig a bottom drain very easily using toilet bowl flanges (one below
the liner and one above) and terra-cotta "bowl" type planters for the
anti-vortex. If you can get the type of anti-vortex that has an airdome
attached, it will accomplish two things: a) it will aerate your pond for
you, and b) the rising bubbles actually draw the bottom stuff towards the
drain.

Alternatively, if you're using one of the retro-fit drains that sits on TOP
of the liner instead of through it, it will be powered by a pump, so a 2"
drain can be used. Pumps do better at pushing water than pulling it, but it
"can" do the job. The downside is that a pump will macerate (grind up) the
poo instead of drawing it out in larger pieces, which will make cleaning the
debris from the water column a bit more complicated. However, you have to do
what you have to do. *Any* is better than none.

Lee

"Fernando Rivera" wrote in message
...
I would like to know if anyone can help me out with a couple questions. I
would like to add a bottom drain to my pond with having the plumbming on
top
of the liner, is this possible? It's to late to redo the pond and less
cost
effective. Is there any ideas or suggestions, any help would be
appreciated.
My pond is currently 12,000 gallons. And i would like an easier time of
cleaning the bottom.