There is a nut just below the 'T' bar handle on my mains water stopcock. It has an ultra slow leak. I have tightened it a quarter turn and all seems fine, but when I check the next day there is a ring of water around the threads. No matter what I do I can't get rid of it, it just slowly seeps through after a day or so.What do I need to do to fix this?
Do I need to replace the olive or wrap PTFE around the thread and retighten.