Once you are done, test it out! Remember you need a drainage channel so you don’t flood the rest of your house/area. When you press the button for the second time, the dispensers should pickup the water and you are ready to replant.
It’s very important to note that water can only travel a certain distance, which is 7 blocks. At 8 blocks, the water stops flowing and won’t go any further, even if there’s a ledge in front of it, however if the water goes down another level, it resets this distance. By using this method, your automatic farm can be set on a large slope. Lighting is also important, because without lights, plants don’t grow, so make sure you at least place some glowstone down.