Hi there, I just have a quick and probably dumb question. How can I tell the difference between an HPV valve with flow control and one without flow control simply by looking. I need to replace the one I currently have and I have no clue which one I should get. I can't find any numbers on the thing except 75-1026 which is hand written on the side and perhaps I am even misreading that. Any suggestions? Mine is currently being used on my ground source heat pump not any irrigation system...sorry. I ...
