self powered pump/filter

"cruxaustralis" wrote in message
...
During a break from digging my pond, and basking in the warm Queensland
sunshine it occured to me that I could use the hydraulic pressure of the
pond to pump/siphon water into my veggie filter. So i built a model using
a
20 liter drum and it's been pumping/siphoning away like a beauty for a
week.
I used a network of 12mm poly irrigation pipe in the bottom of the drum
and
initially primed/siphoned the outlet line into a plastic tub, about a
metre
head..with an overflow outlet back to the drum...topped up the level as it
got pumping and voila!.
A search of the web has rewarded me with no links to something similar..so
now I'm beginning to worry that I am missing something obvious in my new
found enthusiasm.
As a result I now have a niggling doubt that this will all fail when
scaled
up.
Anyone have a clue that might save me from a fundamental error when the
real
thing is needed?



Not possible, defies the laws of physics.