I used to work for a geothermal power company as a well field spe******t. We installed lineshaft turbine pumps as deep as 2000', and most of these wells had a static water level from 600' to 1000' below top of well. There were no checkvalves anywhere in the column pipe. There was one located about 40' downstream of the discharge head.
When we would start these pumps, it would take anywhere from 20 seconds to a minute for the water to reach the surface. This tells me that the water level in the pump column pipe was somewhere near the static water level of the well. If the column stayed full, it wouldn't take any time for the water to reach surface. There were no vacuum breakers etc. on the systems.