I can provide you the answer my partner gave me to the same question. The bidet provides water with a direction to it. You wash front to back, so all the material is lifted and pushed further away from the vulva and only fresh clean water arrives at the vulva itself. Also, as in chemistry, dilution is the solution, as you are washing less and less undesirable material left and the water runs cleaner and cleaner. So take extra time, wash front to back, and do multiple slow passes.