The Greywater filters have one main function, that is to remove all the large particles (hair, lint) from the greywater. They have two sections; the filter tank and the surge tank. The filter tank holds the filter. The surge tank temporarily holds the water. It’s important to use a surge tank opposed to a holding tank because a holding tanks requires inspections and a higher priced permit. A surge tank does not require inspections and the permits are sometimes free or very low priced