Hello everyone, I've been lurking these forums for a while now and am very impressed with the wealth of information presented! Now it's time for me to ask for some advice. I had a new boiler installed about 4 years ago and recently have noticed one nipple that is starting to rust out. The nipple is between the backflow preventer and what I believe to be a pressure valve. The nipple at the bottom of the pic is connected to the hot pipe coming from the boiler. See the attached pic. Should I replace this with a dielectric nipple to avoid anymore future corrosion? What I find interesting is the nipple below the "pressure valve" doesn't show any signs of the similar corrosion.