Begin by looking at the various pipes and fixtures you can see in your home. Inspect them to determine their material. Common residential materials include:- Copper: Rigid, with a reddish-brown color.- PEX: Very flexible, often colored red or blue.- PVC: Plastic, typically white or off-white.- CPVC: Plastic, similar to PVC, with a color and texture almost indistinguishable from that of PVC.- Galvanized steel: Heavy, with a satin, metallic-gray finish.Next, check the actual functioning of your plumbing system. If your home has a basement or a crawl space, these may be ideal locales for seeing the plumbing layout easily. Check pipe configurations, if you can see them, and any fittings or joints, as these may also give you clues to the working pressure of the plumbing system and its residential type. Finally, if you have any home inspection reports or maintenance records, see if they contain any internal assessments of your plumbing. If you're not sure about your plumbing type, or if you suspect any problems with it, consider hiring a plumber for a comprehensive evaluation.