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? 

• 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.