We have a water sprinkle system in your yard. Our 1 year old dog loves to play with it and bites on it. (read breaks it). My question is is there something as a metal sprinkler (for the dog pen)??
your best bet is to move the sprinkler out of the pen if possible. in my 17 years as a pro i have seen this often. the only solution is to move the sprinkler out of the pen, or run the sprinklers when the dog is inside. they do make brass heads but he may still break them off at the fitting. hope this helps