This is an odd one. I have an older home with well water, very hard and very salty to boot. I have several whole house filters set-up and a good softener, just to give some background. The house originally was all copper but I have replaced some of it with cpvc as I've done different projects. About four years ago I replaced the bathroom faucet and both supply lines (copper to cpvc). After about a month, the water developed a bad odor, almost like rotten eggs. Changing filters makes no difference and the odor is not present at any other distribution points. About two months ago I replaced the kitchen faucet and also swapped copper for cpvc in the supply lines. Again, about a month later, the odor. It seems to dissipate after running the water for quite some time, and generally the water to the house is not of the best quality, but I do not get the odor from faucets with copper supply lines. Is there something in cpvc that breaks down? It also appears to be more noticeable in the cold water than in the hot, which would go against conventional thinking. By the way, I've been in plenty of buildings that use either pvc or cpvc and have not witnessed an odor problems with the water, so I'm kind of puzzled.