I don't want to sidetrack this conversation by asking dumb questions, but here goes: If it's a bottom dump system into a bucket, what prevents the sheer force of water exiting the bottom drain from making a huge splashing mess? Perhaps I'm overestimating the force with which the water will exit?
A ball valve or such at the bottom with a hose attached would do the truck. You can easily throttle a ball valve. Or even a ball valve at the end of the hose. Six of one, half a dozen of the other.
