banging pipes

My contractor installed these CPVC pipes shown in the photo for a double vanity. When you turn on the hot water on either sink (hot water is on the left on both sinks), there is knocking that starts once the water gets hot and it doesn't stop until about 15 seconds after turning off the water...

Pipes are banging in my walls when I flush the low flush toilet in the master bathroom. The old-style toilet in the hall bathroom is essentially right behind it separated only by walls but doesn't have this problem. I have other low flush toilets in the house (same model), but they don't cause...

Wondering if what I'm dealing with is water hammer, and what a solution would be. Happens as my washer is filling at the beginning of wash cycle, and again when it fills to rinse. Only way to stop it, is to stop the washer from filling and run upstairs to turn on the water in the bathtub. If it...