A leaky shower faucet (single handle) is driving me to my grave. I finally found a replacement cartridge (Danco VA-1). I installed it and it still leaks. I removed the cartridge and found that there was significantly more black on the cold side which comes in contact with the valve. The leak is actually warm. I guess the O-ring on the valve itself on the warm side is worn more than the o-ring on the cold side. Can these o-rings be replaced on the diverter valve? And what do I use to do this?side of