NDS 420 Green Plastic Spring Loaded Pop-Up Drainage Emitter for 3" & 4" Drain Fittings discharges stormwater captured upstream by catch basins, channel drains, and other drainage solutions and carried downstream with connected drain pipe. The spring-loaded emitter cap pops up to 1 in. high to release water when pressure builds, disperses water at up to 56 GPM, then automatically retracts once flow diminishes. Cap stays closed when not in use to prevent debris and rodents from getting into the drainage system. The Pop-Up Emitter connects to 3 in. & 4 in. sewer and drain fittings which connect to sewer and drain pipe and triple-wall pipe. Cap and cover made of high-density polyethylene (HDPE).