At some point there was a thread about replacing low point drain valves on the hot and cold sides, unfortunately, searching is not leading me there. On a recent trip our 2015 Rockwood 2318G developed a very slow leak from the low point drains. In our popup the T-Handle valves are located under the sink and cooktop. There is no pipe that exits the trailer, just one end of a 90 degree valve that looks like those in the attached picture. After removing the T handle it appears that the O rings are degraded. I would like to replace the O rings first to see if that corrects the problem, which is likely. If not, where might one purchase such an item? Thanks much.