Take care mixing materials
The Coefficient of Expansion differs between metals and plastics. Most metals expand more (at the same temperature) than most plastics. Hence:If you thread a male plastic fitting/nipple into a female metal hub, the connection may leak when hot (Hub expands more than insert).If you thread a metal male fitting/nipple into a plastic female hub, the hub could break when hot (Insert expands more than hub).You also want to ensure that any metal fittings are galvanically compatible /w each other (or corrosion could result).HTHGord