Know the difference between storm drains and public septic systems? Public sewage systems collect wastewater from household drains and toilets and send the contaminated matter to treatment facilities to clean and properly dispose of. Storm drains are the opposite: They collect excess rainwater and dispose of it directly into natural water sources. In the fall months, be careful to not dispose of grass clippings and leaves into storm drains. Not only can it create blockage and cause flooding, but grass clippings from chemically treated lawns can end up polluting natural waterways, ultimately contaminating public water supplies. Instead, compost leaves and grass at home or bring them to a commercial composter to be made into beneficial mulch.