I used one at Nightshade Manor. It was installed on one side of a 4' wide hallway. It was effective but it would have been even more effective if I had two of them, one mounted one each side of the hallway. This way patrons get the effect no matter which side of the hallway they are walking along. Patrons walking along the left side of the hallway did not get hit in the legs by the hoses, but the sound they make provided a startle in itself.
I purchased mine from Ghostride Productions.