The Monolithic Concrete Filter Underdrain from Orthos Liquid Systems efficiently allows the in situ construction of new or retrofit suspended floors that become part of the civil structure. A broad range of filter nozzles enables optimum performance on backwash and air scour cycles. The filter nozzle density across the filter floor can be engineered to specific requirements; standard spacings are 6- or 8-inch centers. Higher filter nozzle density reduces problems such as rat-holing and mud-balling and reduces the need for specialized support media. Higher density is particularly useful where finer media is in direct contact with the filter nozzles, and where refurbishment requires deeper filtration media. 843/987-7200; www.orthosnozzles.com.