to much water washes the soil on to the leach field were it blocks it up. The longer the water and soil sit the better it settles or floats depending on what it is. only the water would get out into the leach field in a proper system unless you run to much water to fast.  Thing to do is run your shower water outside in it's own drain area, but it may not be allowed where you are. Used to be called gray water system.  Look it up.