Pipes freezing?

Hi all,

I have a large (about seven thousand gallons) double pond with a
waterfall ledge between them. When it gets REALLY cold that ledge
freezes over and the water rises higher and higher until it goes over
the uppper pond's edge and floods the area. For that and other reasons
I've decided that I just want to pull the pump and let it freeze. BUT,
I don't want to have my pipes freeze and burst. With this size of pond
there is an external pump of course which sits outside the pump, but
below the water level. I have a pipe coming out of the ground for the
bottom drain and I'm afraid that if I turn everything off and pull the
pump that that part of the pipe will freeze and crack. Am I being
paranoid or is this a real fear? If it is a real fear, how can I prevent
that exposed three feet of pipe from freezing and breaking? I'm using
schedule 40 80PSI three inch pipe, if that helps in the decision making.
All my other piping will either be empty or three feet under ground.

Can anyone help me with this? I'm tired of the overflows or the cost
of running a heater to keep it thawed at the falls. Oh, the pond is
four feet deep in the bottom pond and three feed deep in the upper.

thanks,
DLC
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* Dennis Clark www.techtoystoday.com *
* "Programming and Customizing the OOPic Microcontroller" Mcgraw-Hill 2003 *
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