House this one inside a lock box so if it blows there is no shrapenel. Yes Yes water valve instead of an air valve I know. Im not condoning it Im just passing along information. I always just buy air cannons as they arent that pricey and liability wise I like having a seperate manufacturer.
I like the minions web air cannons myself.
For the water, buy from a haunt vendor- establishing a relationship is great and they really arent that much more expensive.