Hello everyone, I previously posted the question on the wrong forum category, I was at a constriction site yesterday and notice this situation that I would like some advice and clarification on. The house has the required 2 grounding rods outside properly connected to the electrical panel and to the exterior water spout, but I notice inside the house that the water piping is PVC. T the installed tankless water heater, there is also a grounding wire connected to a copper pipe coming from the tankless water heater that connects to PVC piping before entering the wall. Is this to bond the appliance or to add additional grounding to the electrical system? basically what I want to know if in this case, the bonding is just for the appliance or to use the home piping as additional grounding, Thank you very much.
It could have been run to bond the water piping system if it were all metal. Since there is no complete metal piping system bonding of the small section of copper pipe is not required. If the heater connection is all metal the short sections of pipe are already bonded to the EGC (equipment grounding conductor) run with the branch circuits.
Thank you, Robert for the clarification, so this grounding is basically redundant.
IMO yes. The NEC requires that a metal piping system be bonded but you do not have a metal piping system.
Me thinks this is a déjà vu or Groundhog Day moment?
Robert 
I’m new here and posted previously on the wrong forum category, but all good now, thanks!!
You’ll get the hang of it Mauricio and we’re glad you are here. 
Thank you Larry!!
Your doing great:-) Not to worry.