I always assume that the pump was only used in sparging, and could be used for fly-sparging, where a "sprinkler" would lightly deliver the liquor onto the mash bed at the rate of run-off.
I put a cheap pie pan with a bunch of holes in it on top of the mash and use a long enough hose so the end is under the surface. This also helps keep the circulating fluid spread out and the temperature uniform. You could also use a hose clamp to reduce the flow.