Older buildings almost never have a single pipe material. Original galvanized supply lines may meet copper repairs, and cast-iron drains may switch to plastic where a past leak was fixed. Recording what you see, and where the materials change, gives a plumber a head start and helps you understand quotes.
You only need a flashlight, a small magnet and your phone camera. Do not cut, scrape or disturb pipe while you look.
How to tell materials apart
| Material | Color and look | Magnet test | Joints |
|---|---|---|---|
| Galvanized steel | Dull gray, may show rust | Sticks | Threaded fittings |
| Cast iron | Dark gray to rust-brown, thick and heavy, larger drain sizes | Sticks | Hubs or rubber couplings |
| Copper | Reddish-brown, may have green patina | Does not stick | Soldered or pressed fittings |
| ABS plastic | Black, used for drains | Does not stick | Glued fittings |
| PVC plastic | White or cream, used for drains | Does not stick | Glued fittings |
| PEX | Flexible red, blue or white tubing | Does not stick | Crimp or expansion rings |
Where to look
Water heater
The pipes entering and leaving the top of a tank heater are easy to see and often show the original supply material.
Under sinks
Look past the flexible supply lines to the pipe coming out of the wall.
Crawlspace or basement
In raised-floor houses, main supply runs and drain lines are often visible under the floor.
Garage and laundry
Exposed pipe at washer boxes and along garage walls is common in older houses.
Outside walls
Hose bibs and the line entering the building near the main shutoff show the service pipe material.
Worksheet
| Location | Supply material | Drain material | Material change seen? | Condition notes |
|---|---|---|---|---|
| Water heater | ||||
| Kitchen sink | ||||
| Bathroom 1 | ||||
| Bathroom 2 | ||||
| Laundry | ||||
| Crawlspace / basement | ||||
| Main shutoff |
Questions to bring to a plumber
- Did I identify the materials correctly?
- Where do old and new materials join, and are those joints sound?
- How much of the supply piping is still galvanized?
- What drain materials are under the floor and out to the street?
Common questions
Why does a magnet help?
Galvanized steel and cast iron are iron-based and attract a magnet; copper and plastics do not. It is a quick way to separate old iron pipe from newer materials.
What if paint covers the pipe?
Painted pipe can be hard to judge by color. The magnet test and the type of fittings still help.
Can I tell drain material from inside the house?
Often only partly. Drains under floors and in the yard are usually confirmed with a camera inspection.
General information for Downtown Fullerton, not a quote or professional advice. In an emergency, call 911.