Where to look
At the main shutoff
The pipe entering the house and the first few feet after the valve show the service material and the start of the house system.
At the water heater
The lines on top of the heater usually change from a connector to the house piping within a foot or two.
Under sinks
The pipe coming out of the wall behind the shutoff valve is often a short stub of the same material as the line in the wall.
In an unfinished area
A mechanical room ceiling or crawl space shows long runs and the fittings that connect them.
On a manifold
If you find a panel of small valves near the water heater, the house is very likely plumbed in PEX.
Identification table
| Material | Look and feel | Markings and fittings | Winter note |
|---|---|---|---|
| Copper | Rigid metal, orange-brown or dull brown, green spots at old joints | Soldered or pressed fittings; sometimes a colored stripe print | Splits and bulges when frozen |
| PEX | Flexible plastic in red, blue, white or gray | Printed PEX lettering; crimp, clamp or expansion rings | Pipe tolerates ice better; fittings are weak spots |
| CPVC | Rigid plastic, cream, tan or off-white | Printed CPVC lettering; glued fittings | Becomes brittle; can crack in cold and with age |
| Polybutylene | Flexible plastic, usually gray, sometimes blue outside | PB stamp; plastic or metal crimp-ring fittings | Many owners and plumbers choose replacement |
| Galvanized steel | Rigid gray metal, threaded joints, magnetic | Threaded fittings with visible pipe threads | Corrosion inside plus freeze stress at threads |
What to do with the answer
- IfYou find polybutyleneThenMention it to your insurer and plan a conversation with a plumber about replacement, especially before winter.
- IfYou find older CPVC that cracks or yellowsThenHandle it gently and ask a plumber to look at any lines in cold locations.
- IfYou find PEX with a manifoldThenLabel each manifold valve so a single line can be shut off during a leak.
- IfYou find a mix of materialsThenThat usually means past repairs. Ask whether transitions between materials were made with the right fittings.
General information for Parker, not a quote or professional advice. In an emergency, call 911.