I have about 20 ball valves on my boiler setup counting all the zones both in and out plus some others. Contractor installed them about 20 years ago. They look like good quality valves but have no name on them. I had one of the zones drained for a few years with the small brass drain cap sitting next to it. Well it turns out the cap is now missing. Should be an easy solution, just take a brass drain cap off an old valve or buy a replacement cap at HD. Well it turns out the brass drain caps on my ball valves are 3/8" course thread (16 threads per inch). All the caps I can find from old valves or replacements at HD and online are 3/8" fine (24 threads per inch). I would hate to drain down the boiler and sweat in a replacement valve for such a simple problem. So far the only possible solution I have found is to buy a SS 3/8" course thread cap nut. The nut is actually too deep but I could probably just fill it with some Teflon valve packing material but I would really find a better solution. Any ideas?