There are two possibilities, one through the wall as you mentioned, the
other a siphon over the top. Either will work. I have bottom drains
plumbed through the liner into the front of my skimmers. You just need to
have an appropriate size bulkhead fitting, clamping the liner to the tank.
You could also use the Bickal Boot for the liner and not worry about the
watertightness of the tank. My bottom drains are just pipes that end
pointed down in the deepest part of the pond, but they make commercial non
vortexing bottom drain units. For your size tank, I would think that the 2"
by Tetra would be more than ample, and it is designed as a retro drain, not
requiring a hole in the bottom of the liner. The plumbing can then go over
the top and back down to the pump, and work as a siphon.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"DesertPond" wrote in message
...
I've got a 400-gallon round galvanized tank (with liner) that I use
for quarantine purposes. I'd like to use some sort of bottom drain
setup for it but I'm not sure how to go about it. Not sure if it's a
good idea to drill a hole through the side for pipe access.

Any suggestions?

thx