Media filter drainage systems or underdrains are an important part of filter design and operation. If they are not installed properly, the filter will not meet the expected treatment level. Filter systems collect and clean effluent and deliver it to the next part of the treatment system. Drainage systems are sometimes made by the manufacturer as a part of the product. Other times, the installer constructs the system. In either case, the drainage system must be watertight so that the effluent leaves the filter and flows onward without leaking into the soil, and so that the filter does not collect
