[IanW]

While it is certainly better to use components that are rated for air pressure, I found in my own (not too extensive) research that large enough solenoid valves (1" diameter) would be prohibitively expensive for some teams. However, if you know of some source that has such valves for cheap, I would definitely look into it.

And before someone says that an catastrophic failure would also be "prohibitively expensive," I guess that's just something teams will have to consider. I suppose the other option is to just wrap the sprinkler valve in layers (and layers (and layers)) of duct tape.