I decided to install a brass union below the hot washin g machine faucet to make it possible to remove/replace in the future. It is a 1/2" sweat connection on one side and 1/2" threaded on the other. I ended up using two wraps of teflon tape over the brass seat to keep it from leaking (I know tape is not suppose to be used but nothing else seemed to work to stop it from leaking and the pipes were aligned straight). Should I be concerned about closing this union in the wall behind sheetrock? After three days, there are no leaks. Is it common for unions to loosen up over time and start leaking from water hammer or vibrations?