volunteer, I am not familiar with the specific valve model but generally, all such valves take some time to close. There is usually a transfer port through the valve body; this bleeds the water from the underside of the diaphragm as the spring presses down it when the water is shut off. Check that this port is clear. It is always beneficial to install a filter in the water supply line ahead of the manifold. This reminds me to clean the filter on my system this week-end.

I have fixed so much on this system that I forget somethings at times. I wonder if one of them has an impact on this situation... there are two cracked pipes left to fix. One in Zone 2, one between or in either Zones 3 or 4. One of the valves that won't close is Zone 3. The cracks are causing a significant amount of pooling on the ground. Significant being in the gallons not cups range. Someone drove posts into the ground and caused these and more broken pipes most of which I have fixed. Would cracked pipes cause valves to operate incorrectly? Maybe lack of proper pressure? The zones do spray, they don't really look like they are weak pressure wise. Maybe the cracks are letting in debris which clogs up the valves after they are clean? Do I have the cart before the horse inthat it is senseless to try to fix valves and adjust heads, etc. until the cracks are all taken care of?

The pipe breaks won't affect the valve function unless the breaks are before the valves. It sounds very much like you need to replace or rebuild the valves. Diaphragms work harder than any other part of an irrigation system except for maybe the pump on a pump system. They generally need to be replaced after 6 - 10 years. Toro, in my experience fail sooner than other brands and are also the more difficult to rebuild. (many more screws and parts). Also 11/2" and 2" valves do take longer to shut, usually 20 - 45 seconds, but if they do not shut at all even once, you either have a foreign object underneath the diaphragm, a bad diaphragm, or the spring is missing on top of the diaphragm. Hope this helps.