We found that the drain port with the raised edge inside, with a drain line that has a rubber fitting that seats into this edge, seals better for the newer types of washers. With the front-loading washers, a drain line that doesn't have this fitting used in the traditional open-line drains (knockouts opened) must be secured to empty at a certain height in the drain - too short and there may be liquid coming out of the drain port, too long and you can siphon back drain water into the washer. The manual for the washer will provide those specifications. I think for ours it was 5 1/2" to 6 1/2" inside the drain port.