a couple of months ago, my front lawn sprinklers started staying on after their zone turned off. This, in a system that has been running continuously for 13 years. OK. It's the valve, I thought. So, I got a replacement valve, and started to work. Before getting TOO involved, I decided to take apart the old valve first. When I did, I found a small piece of gravel inside that had been getting caught, keeping the valve open. My only thought was... "HOW did it possibly work for 13 years before causing a problem???"