The video says that they toke the water from springs under the pyramid. If the spring has enough pressure to make the water climb to 150 m, then just opening a vertical hole you must get a 150 m water jet. (Really, the water in the jet moves faster, so it has more internal frictions with the spring wall.) In Yellowstone, Old Faithfull has 50 m water jets, but it’s a geyser, not a cold spring with a lot of water.
Were they slaves? I've often seen reference that they were citizens working on the pyramid as payment of taxes in the form of manual labour, add to that your boss and the building were being built for, who to them was, a God.
I'd say whatever the most simple explanation is the answer I could see either rubble or ramps.
http://youtu.be/C1y8N0ePuF8?t=15m20s