27 feet is not very deep. Is that to the top of the screen or the bottom of the sand point? If the ground conditions allow it, a sand point should have about 30 feet of pipe above it. This ensures that the pump cannot draw the table down to the top of the screen.
Drive couplings are designed so that the pipe ends bottom out and as such may not have as tight a seal on the threads. For that reason they need to be well doped.