Cast iron pipe is recognizable by its black finish and the bulge at the end of each pipe section, called a “hub,” that the adjacent pipe fits into. Surface rust may eliminate the black finish on extremely old cast iron, leaving it simply rust-color. It was installed for new construction up until the late-1960s for drain pipe only and is still available, but only used for repairs.
It is approved for drain/waste/vent, not pressurized water supply, and cast iron is mostly concealed in older homes where it is still in use. The places it might be visible are at the laundry as a the standpipe behind the washing machine, in the attic as a vent pipe through the roof, and as exposed drain pipe from plumbing fixtures above it in the crawl space under a home with elevated wood floors.
Corrosion eventually eats completely through the pipe, allowing sewage to drip out. Although the rust-through is at the back of a vertical pipe in the photo below, it occurs more often at the bottom of horizontal pipes in a home’s crawl space.
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Here’s links to a collection of our other blog posts about PLUMBING PIPES:
• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?
• Can galvanized steel pipe still be used for new water lines in a house?
• Why can't a sanitary tee be used for a horizontal-to-horizontal drain pipe connection?
• What is the difference between green and white sewer drain pipes?
• Is a washing machine drain hose required to be secured at the standpipe?
• What are the abandoned pipes sticking out of the wall in my house?
• What are the code requirements for plumbing vent terminations?
• What are the code requirements for layout of drain piping under sinks?
• What causes a gurgling sound when a bathtub or sink drains?
• What is a "combination waste and vent" in a plumbing system?
• What is a building trap?
• What is a galvanized nipple?
• What are the pipes sticking out near my water valves?
• How do you accurately find a broken water pipe leak under the floor slab?
• What is the difference between water pipe and sewage (waste) pipe?
• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water?
• Is a hot water faucet handle required to be on the left?
• What is a dielectric union?
• What's that powdery crust on the pipe connections at the water heater?
• If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the problem?
• How can I tell what type of plumbing pipe I have?
• Why is there a flexible accordion pipe under the sink?
• What is the difference between PVC and ABS plumbing pipe?
• What is the difference between water service pipe and water supply pipe?
• What are the pipes on my roof?
• How can I find out what type of water pipe runs underground from the water meter to the house (service pipe)?
• What is a P-trap?
• Why is old galvanized steel water pipe a problem for homebuyers?
• What does polybutylene pipe look like? Why is it a problem?
• Which water pipes are an insurance problem and possibly uninsurable?
• Can you connect CPVC pipe directly to a gas water heater?
Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.