I had a similar situation with the replacement of my failed 90 degree main water supply valve, with a flare connection on the incoming pipe.
I wanted to use a more reliable ball mechanism 90 degree replacement valve. After some research, which confirmed that reusing a flare connection should not be an issue, I had the
part I needed special ordered from HD, at a very reasonable $34.65 + tax. Here is the manufacturers
link.
The original flare connection had pipe dope applied to the threads and I cleaned the female threads to the extent that I could and I didn't apply pipe dope to the new male flare threads as the flare connection seal is mechanical and therefore the threads shouldn't require pipe dope as the seal is made ahead of them.
The new valve did not have a drain thread on it so on the vertical run, approximately 5" above the main water supply valve, I put a T fitting with a washing machine ball valve on it. After installing the 4 new valves & fittings;
- main valve
- 3/4" male NPT to 3/4" Sharkbite adapter
- 3/4" x 3/4" x 1/2" Sharkbite T
- 1/2" washing machine ball valve
I had the water company come and turn on my main supply in the front yard. Initially all the connections looked good though, due to me forgetting to close the washing machine valve before opening the main supply valve, there were splashes and drips all over the valves and fittings. After drying everything I discovered I had a 5 minute interval drip coming out between the female threads and male threads of the flare connection. I thought a minor tightening of the flare connection would do the trick, however the opposite occurred and I turned a 5 minute interval drip into a 15 second interval drip. I called the water company again to get the water shut off at the meter and then made a quick trip to get some pipe dope. I applied the pipe dope as specified above, "dab a small coating of pipe dope around the mating surface" of the male fitting, and don't over tighten. I called the water company and they turned the water back on and the joint remained dry after a 30 minute observation period.
Thanks Jim & Smith333