We have well water coils for pre-cooling in commercial air handlers. The tubes are copper and the fins are aluminum. Sections of pvc pipe are connected to the inlet and outlet of the coils between the coil and sch 40 steel pipe which is the majority of the piping. The copper tubes have been getting pinhole leaks in less than 2 years after installing new coils. There is a green color on the inside of the pipe at the location of the pinholes. I had one source tell me that this is electrolysis and that the pvc is not an adequate dielectric. I was told that we shoud put a brass valve (and remove the handle) between the coil and the pvc pipe to prevent electrolysis. Does anyone have experience with pvc pipe connections between steel and water coils and experiencing this problem. We have checked for sand or other abrasives and have not found any and have never found a shiny surface on the insdie of the coils. The flow rate seems to be withing the acceptable range. This is becoming a very expensive and frustrating problem. Any ideas? Is this really an electrolysis problem?