This is a very old thread but I too have come accross this same problem. I called Toro today and they are sending me four gaskets for my valves( TORO 53285 ) that they claim have been improved and should last. They also said they will continue to carry them for years down the road. It is a known problem for this valve. I like this valve since it has a union in the middle for easy removal. Hope this helps anybody looking for this part.
