I did not look at the picture on your post earlier. the nipple on the cold water connection in the photo is shipped by the water heater mfg that are delivered to plumbing suppliers and are used to prevent a galvanic reaction. Because the fittings add about $5.00 to the cost of the heater retail stores such as Home depot buy their heaters with out the nipples. Most of the problems occur when water heaters are installed by homeowners that do not know any better or by the plumber that works out of the back of his truck