Ted,

Thank you for your reply. I agree with your thoughts of running one piece of thick wall tubing but my plan is more a result of convenience than anything else.

The pond is 80' in diameter. I have a 50' length of 1/2" weighted poly, which will get the diffuser to the middle of the pond. The 20' of 1/2" PVC gets me from the pond edge to the compressor.

I tried an "experiment" yesterday and took a small section of the poly and attached it to a brass fitting and PVC coupling. I taped off the ends, placed the whole deal in a container of water and put it in the freezer. I'm sure this doesn't fully mirror the winter conditions of ice but I thought it was worth a try. This morning it was a solid block of ice with no damage that I could see. I'm going to leave it in the freezer for now while I work on the rest of the system.

Russ