When did builders stop using cast iron drain pipe?

The dates that can be traced to a published source are these.

• Early 1950s. According to the Plastic Pipe and Fittings Association (PPFA), "ABS pipe and fittings were originally developed in the early 1950s for use in oil fields and the chemical industry."
• 1959. The same guide says "In 1959, John F. Long, a prominent Arizona builder, used ABS pipe in an experimental residence, which he built to test the latest ideas in effective, cost-cutting building supplies." An Arizona builder was running an early test.
• 1960. The PPFA guide says "In 1960, the FHA approved the use of ABS pipe for DWV applications." DWV stands for drain, waste and vent, the pipes that carry wastewater out and let air in.
• 1967. Charlotte Pipe and Foundry, which has made cast iron pipe since 1901, says it has "been manufacturing plastic plumbing systems since 1967." It is one of the makers that sells both materials.

The American Society of Home Inspectors (ASHI) describes the change from the plumber's side. Its article says "Since the late 1950s, plumbers have been introduced to a wide variety of plastic pipe and fittings" for drain, supply and vent use, and that "Some plumbers were slow to make the change from metals to plastics."

Put those together and you get a slow handoff that starts around 1960, not a cliff. The written record doesn't give one year when cast iron ended in Phoenix homes. Home age helps as a clue but doesn't settle it, because builders changed at different times.

ASHI gives the short reason: "code acceptance, the ease of installation and the economics of construction caused most to accept and even embrace the change."

The PPFA guide, written by the plastic pipe trade group, spells out what builders were weighing. Its case for ABS includes weight (it says a 3-inch, 10-foot section weighs under 10 pounds), a one-step solvent cementing process with "No threading, no primer, no lead pot and torch required," and lower cost than metal pipe. It says a drain installation in a typical two-bath home, with about 100 joints, "can be completed two to six hours faster with ABS pipe than with other materials."

The guide also tells a durability story. It says that 25 years after the 1959 Arizona house was built, "an independent research firm dug up and analyzed a section of the drain pipe. The result: no evidence of rot, rust or corrosion."

Keep the source in mind. That is a trade group making the case for its own product. It explains why a builder would switch. It doesn't say cast iron failed, and it doesn't say every plastic pipe aged well. ASHI notes that between 1984 and 1990, five manufacturers of ABS pipe "allegedly manufactured ABS pipe that sometimes cracked circumferentially at pipe joints, resulting in leaks," while the article's author says he has never encountered that leak himself. The lesson is small but useful: age and material both matter, so identify the pipe before you judge it.

Yes, cast iron is still allowed and still made, which surprises people who assume it is obsolete. The 2024 International Plumbing Code's drainage chapter still lists cast-iron pipe among the materials allowed for above-ground drain and vent pipe (Section 702.1), for underground building drains (702.2) and for the building sewer (702.3), by three standards: ASTM A74, ASTM A888 and CISPI 301. Arizona cities adopt their own code editions and amendments, so check your city's rules for a specific job. See which codes Phoenix enforces.

The manufacturers still sell it too. The Cast Iron Soil Pipe Institute's FAQ page describes CISPI 301 as the "Standard specification for hubless cast iron soil pipe and fittings for sanitary and storm drain, waste and vent piping applications." Charlotte Pipe says it has been "manufacturing cast iron pipe and fittings since 1901." The cast iron makers' trade group argues its side, too: the Institute's FAQ page describes a brochure that compares plastic and cast iron on six points, including fire-resistive construction, underground crush and deflection, and sound attenuation.

Mixed systems are normal, too. ASHI notes that "Plumbers sometimes combine plastic and cast iron DWV systems in a manner that helps reduce sound transmission," and that old cast iron and steel traps are sometimes swapped for "newer, better draining plastic traps." So finding both materials in one house doesn't mean something was done wrong. It can mean a repair, a remodel, or a design choice.

Start with any drain pipe you can see: under a sink, in the garage, in the attic, or at a cleanout.

• Plastic drain pipe comes in two common kinds, ABS and PVC. ASHI notes that customers call ABS "the black PVC," though it is a different plastic. The PPFA guide says ABS is assembled by solvent cementing, so joints are glued.
• Cast iron is metal pipe rather than plastic, so it looks and sounds different when you tap it.
• A mix often shows up at a repair. ASHI says no-hub bands are "often" used "to connect unlike materials such as ABS to steel, cast iron and even other plastics."

Most of the drain is out of sight, though, and slab homes bury a lot of it. If your home was built in the 1960s, 1970s or earlier, a camera look is the reliable way to see what is under the floor. See how a plumbing camera inspection finds problems, and why older Phoenix homes have their own plumbing issues.

If you have plastic, there's nothing to change because of its age. If you have cast iron, the age of the house tells you how long the pipe has been in service, and slow drains, odors or repeat backups are the signs to watch. Signs of old, failing pipes lists them. Buying an older home is the moment to have the line looked at; should you get a sewer scope before buying explains why.

HQ Plumbing & Air offers a sewer camera inspection so you can see the pipe material and condition without guessing. We're licensed and insured, we give free estimates, and the price is upfront before work starts.

Here's the takeaway. Plastic became an approved option in 1960 and cast iron never went away, so check the pipe, not just the year on the deed.