I have 3 low point water drains in my trailer (Picture) that have PEX pipe plastic caps on them. The caps are OK but I would like to replace them with simple on/off valves. I have checked the local plumbing supply stores for such a valve but they don't know what I am looking for.. I am looking for a light weight nylon/plastic valve that would easily install on these lines with common tools. Ideas?? Suggestions??