How to connect ductile iron to copper pipe

[canman]

Need help. I have a 4" ductile iron pipe, class 53, for domestic water use coming from the downstream side of a backflow device. It needs to be connected to a 4" copper pipe, type K for on-site drinking water use. Specifically, what technique should be used to connect the two for cathodic protection? If you have a certain manufacturer and model of a part that would be very helpful.

Canman

 

[Metalguy]

You should electrically isolate both sides. A short connector piece of PVC could work, or you can use insulating flanges and bolt washers. Just make sure that both sides are connected to the same conductive support--should have high resistance across the two flanges.