If I was to do this, this will be my setup.

Pipe from Bottom Drain will have a backflow device in line, then to a pump
that empties into a biofilter that is elevated, then by gravity into my
veggie filter, then by gravity back into my pond.

Should the pump fail, the backflow device will stop the water from the
biofilter from going back into my pond thru the bottom drain. With this
setup if your pump fails then there will be no backflow into the pond.

The pipe breakage issue is a different problem that can be corrected with a
level switch similar to what you have in your fuel pump. Get this type of
switching device from your local plumbing supply store, connect the switch
to your pump. If the level goes below a predetermined level, then your pump
will shut off. (I will do some research into this myself soon and will
report back to the group)

Good luck, and keep your questions coming as I am learning a lot from the
answers you are getting.
--
_______________________________________
"Architecture is the ultimate erotic 'object'."
Bernard Tschumi, "Architecture & Transgression"

http://community.webshots.com/user/godwino
"Dan" wrote in message
...
My bottom drain empties into a settling/veggie pond and is pumped from
there
into a bio-filter where it falls back into the main pond. The pump intake
from the settling/veggie pond is above the bottom of the main pond so I
never risk emptying the main pond. Over this winter, I had a leak
somewhere
in my underground plumbing and my water level did drop but when it got
below
the intake of the pump, the pump just shut off.

"BenignVanilla" wrote in
message ...
For those of you with a bottom drain...how do you protect yourself
against
emptying your pond if there is a failure somewhere upstream from your
bottom
drain? Originally I was going to sit my pump on a shelf to protect
against
this, but now that I plan to have a bottom drain, I am concerned. I am
routing my water to a veggie filter that may or may not be attached to
the
main pond via a stream. If it is, I am concerned with the stream getting
blocked and emptying my pond. I am seriously considering not having a
stream
and routing the water back via pipes to prevent this.

--
BenignVanilla
tibetanbeefgarden.com
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