How do I keep sediment from clogging my plumbing fixtures?

I have fairly new copper plumbing and a two year old tankless water heater and I am having a problem with a sediment containing black, white and grey particals cloging my shower head and my bath tub filler. I even had to clean out the hot valve itself on the bath tub. I have allready instaled a sediment filter where the main comes into the house and it didn't help.