The PL-525 is ideal for septic tanks or the primary tank/chamber of a commercial treatment plant. It is also used in commercial grease traps and other solids retention tanks. PL-525 Effluent Filter is rated for up to 38,000 litres per day making it one of the largest filters in its class. It has 1.6 mm filtration slots. Like the Polylok PL-122, the Polylok PL-525 has an automatic shut-off ball installed with every filter. When the filter is removed for cleaning, the ball will float up and temporarily shut off the system so solids won’t leave the tank.