Replacement germicidal ultraviolet lamp for the Wallace & Tiernan WTL200 UV disinfection system, original part number AAD4717. A germicidal lamp loses output steadily through its life while continuing to strike normally, so it is replaced on hours run rather than on failure — running past the rated life is the most common reason a system quietly drifts below its required dose. The matching quartz sleeve for this reactor is item 4108-0609 (800 mm, original part number AAC6190). Wallace & Tiernan is an Evoqua Water Technologies brand, and was part of Siemens Water Technologies before that, so the same equipment is catalogued under all three names and its parts carry Evoqua W3T/W2T and legacy AAC/AAD numbers. Item number 4107-0609. Original part number AAD4717. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.