As we all know, "Ponding" water in low lying areas can ruin the integrity of any flat roof system. So we at Able Sheet Metal have developed a simple and efficient drain to rid the problem without resloping or repitching the existing system. Simply establish the lowest point of such an area by monitoring the receding excess drainage and cut a 5" round whole in the roof. Roof in and pipe to desired location using 1-1⁄2" ABS. Simple, effective and affordable. Able's Ponding Water Drain". May have Galvanized, PVC, or TPO surface