Pond Boss Forums POND CONSTRUCTION Building a dam Question on the overflow

Two things of concern, depending on the size and type of pipe you choose to use.
If you use PVC, a standpipe on the backside of the dam can freeze and break during a hard cold snap in east Texas.
The screw cap will be almost impossible to put back in place once you unscrew it and a big head of water streams out of the pipe. If you are able to put the screw cap in place, you'll probably have a "hammer" effect in the pipe as the force of water is immediately shut off. Plus, wear rain gear...you'll be soaked.
I'd spring for a valve and be sure to put the standpipe far enough back in the dam to keep it stable, surrounded by dirt. Riprap it well.