Abstract: A filter apparatus for filtering gross pollution from storm water for fitment to storm water traps located at the entry and exit of storm water, underground and drainage systems. The apparatus includes a gross pollution filter basket located below the entry level of storm water into the trap so as to provide a bypass channel to allow a volume of storm water to pass through the trap. SA storm water bypass means is arranged to restrict entry of incoming storm water and gross pollution into the bypass channel while the combined pressure of storm water and gross pollution inside the trap is such that storm water can still pass through the filter basket.The bypass means which acts like a one-way valve is also arranged to allow storm water and gross pollution to pass into the bypass channel when the combined pressure of storm water and gross pollution inside the trap is such that the storm water is restricted from passing through the filter basket.