You should also think through the moment where the flow of water will be, since this is a very important point. If you make a small bath, which you will use only in the summer, then it is not necessary to make a septic tank, it will be enough to organize the stock in a regular ditch, which is located outside the bathhouse. Many people do not think about this issue at all because the water goes through the cracks that are in the floor and is absorbed into the ground, but if you do not want to use it then you need to do water drainage.