An improved apparatus for UV wastewater purification in septic tank systems disposed in piping located between tank and drainfield and method for use, comprised of an inlet end, removable for cleaning, a descending section, a connecting section, a vertical section, with outflow tube, and containing a UV light, having provision for preventing removal when illuminated, with protective tube spanning its vertical length, with a built-in bottom insert with ports therein to restrict passage of solids and a built-in top insert with a port therein to hold the UV socket and photocell which communicates to a remote control panel.