Review on Sioux Chief 660-TK Mini Rester: Female Swivel Nut with Male Ballcock Thread - Brass/Antique Brass by Tim Bunker

I've installed a few toilets, done a lot of renovations, have an engineering background, it's a darn simple setup with not much room for clutter. this part above. I tried one of these to see how it worked before buying more for other toilets. All toilets work properly with no leaks. but it leaked out at the junction between the brass body and the plastic sleeve that screws onto the side of the toilet. A tapered o-ring is installed (I saw another review that didn't have it) and while it was there it greatly reduced water hammer. So I've tried removing it, reinstalling, hand pressing it again - it's still leaking. I've tried tightening it by hand and then adding a 1/4 turn with a wrench (common recommendation for some plumbing fixtures) - still leaking. So I tried another 1/4 turn, then another 1/4 turn - no change, the same amount kept flowing between that plastic collet and the brass body. Removed, hose reconnected - no leakage! Tried again, just hand tight with a 1/4 turn wrench - same leak. Because the leak is between the collet and the body, it means that the cone-shaped o-ring isn't sealing the leak at the threads, so the teflon tape can't fix it. Sorry I think it was too good to be true such an elegant design idea to have a simple contraption right on the toilet connection to absorb shock and eliminate the hammer but if my regular hose fit tight and leak free every time can, and the thing cannot be persuaded or diluted to hold water. it returns. Zero stars if that was an option.