For this short of a run the back pressure would present no problem.Your always going to have condensation (just the nature of compressed air) anytime of the year but not a slug of water as the moisture will be carried to the diffusers and expelled. When the lines are trenched in at even minor depths freezing does not seem to be a problem. My Koender 20ft mill only has the line inground 4 inches deep and I have never used a freeze control on it.Running for the last 6 years this way. I do offer freeze control as an option (Koender unit)on custom built units when and if ice is a concern for winter operation. We recently shipped a system to South Dakota that has a 1 inch poly line laying on top of the ground for 3000 ft to pondside from compressor. We are running 3 diffusers (open water for a snow goose hunting business)www.OutdoorAdrenaline.com
with the Koender freeze control unit tapping into the 1 inch line so that when back pressure of 12-15 is reached ethanol alcohol is injected.Do you know of anything other than RV antifreeze that you suggest as I would like to find a higher % alcohol as RV was suggested by Koenders. Brakeline antifreeze is flammable and may be a problem in some situations however does a great job of removing moisture. In small bodies of water I have a concern about freeze control products in general. "Thanks"