Small leak below main shut off valve

[fish biscuit]

Hello,
As a DIYer this forum has been such a big help over the years. This is my very first post. Just noticed we have a small leak below our main shut off valve. It appears the leak is coming from the threads of the connection to the valve. I'm guessing and hoping a 1/4 or 1/2 turn to tighten will solve the leak. I'm wondering how I do this without compromising the thread on the other side (top) of the valve. If I tighten it below won't the movement of the valve loosen the opposite thread? Do I have to disconnect the valve from the pipe above before I tighten valve? The teflon tape in the photos was my attempt to try and see if I could seal the leak from the outside. Any help or guidance would be greatly appreciated. Thanks,

 

[Tuttles Revenge]

That fitting looks like a flare fitting. It shouldn't need any teflon tape at all to be water tight, but may be using teflon tape to lubricate the threads.

I would disasemble the flare union, clean and inspect the mating surfaces to ensure they're perfectly smooth and round, then reasseble.

More reading. https://copper.org/applications/plumbing/cth/cth_8flrdjts.php

 

[Sponsor]

 

[fish biscuit]

OK I got it apart, cleaned all the threads, put a little pipe dope on it and tightened it back up. Still has a very very tiny leak, about 1 drip every 2-3 minutes. I took it all apart again to try and look at the mating surfaces. I can see one very small imperfection on the flare. I'm guessing this may be the cause of the leak? Is there any easy option to fix this? Maybe a gasket or some kind of sealant? If it is going to require a new flare that is when I will have to let a professional take over which I am trying to avoid to save some money. Thanks,

 

[Tuttles Revenge]

depending on what the imperfection is, indentaion or crack would determine the appropriate fix. The best fix, would be to cut the pipe and reinstall a new union or flare connection assuming its required to have a removable fitting at that location.

The simplest fix might be to wrap a time or two around the cone shaped surface with teflon tape. Essentially forming a soft gasket that would fill in the imperfection. None of the tape needs to be on the threaded portion.