Abstract: A protector for the inlet into a sewer system includes a straight or annular, porous tubular casing for placing on or around the periphery of a sewer grate; a skirt extending inwardly or outwardly from the bottom of the casing for overlapping the side edges of a sewer opening so the grate retains the protector in the use position; and a filler in the casing for maintaining the casing in an expanded condition, at least one of the casing, the skirt and the filler being permeable to water and impermeable to contaminants, whereby water can flow into the system while contaminants are blocked.