Richard,

As far as stuff groing in the pipes, I have pvc piping between bottom drains
and vortex filters and just yesterday noticed the draw down in the vortex
was getting pretty large, indicating reduced flow. I took a piece of rope,
tied a cotton mop head on the rope and pulled it through the piping. It is
now working fine.

As for the stone dust, it is just a fine material, relatively easy to
smooth, like the sand that most people have had recommended, but when
compacted, is more stable. I would think it would be better than sand.

If the bottom drain breaks, you are in deep doodoo. The load as pressure on
the bottom of the pond is only about 1/2 psi per foot of pond depth, so it
is almost nothing. Having the bottom drain anchored firmly so that it
cannot settle and pull away from the liner is important, but there should be
no stresses in the pipe to bottom drain unit.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"Richard Holub" wrote in message
...
At a recent water garden show someone told me that I should not have used
ABS/PVC pipe because bacteria will form inside the pipes causing them to
clog up. Is this true?

Another thought: what are the chances of the bottom drain
breacking/splitting at the junction between the concrete and stonedust?

Rich Holub in Massachusetts