Cast iron pipes in an older home

Cast iron was the standard material for house drains from the early 1900s into the 1970s, so a Craftsman or ranch house in Pasadena may still carry it under the floor and in the walls. The metal outlives most materials, yet it corrodes inward, and an aging stack can crack or scale shut. Our hub on polybutylene and repiping deals with supply pipes; this article stays with the drains.

Can an old house still rely on its cast iron drains?

Sometimes. Published guides give 50 to 100 years for cast iron drains, less when the pipe is buried or sits in wet ground. A house from the 1920s through the 1960s is therefore at or past that range, and a camera inspection will show whether yours has years left.

Failure starts on the inside. Scale thickens on the pipe wall, narrowing the opening and snagging paper and grease, while rust perforates the underside of horizontal runs where waste lingers. Lead-and-oakum joints can loosen over decades. Many Pasadena houses combine cast iron inside with clay sewer laterals outside, so the weak link may be either one. Gurgling drains may be a blocked drain vent instead, and lingering odors are discussed in the sewer smell guide.

How do I spot a cast iron drain that is on its way out?

Look for slow drains and clogs that keep coming back, sewer odors that survive cleaning, rust stains or flaking on any exposed pipe, damp patches on walls or floors beside drain lines, and sinks or tubs that back up. A camera shows the scale, cracks and sags inside.

None of these alone proves the pipe is finished: a one-off clog is normal. A pattern is the warning. If a plumber has cleared the same line two or three times in a year, ask for a camera look before paying for a fourth cable pass. Look at what is visible in the garage or crawlspace: bubbling, dark staining at joints, or a hollow ring when tapped can show corrosion. Odor deserves care, since sewer gas is more than a nuisance. Where a leak reaches a wall or ceiling, ceiling water leak repair explains tracing it.

What will it cost to swap out old cast iron?

Published guides price new plastic drain pipe at around $8 to $14 a foot installed. Dig-and-replace work on buried or under-slab lines runs $50 to $450 a foot, trenchless methods about $60 to $250, and complete jobs span a few thousand dollars up into five figures, depending on access.

That is a wide spread because the work differs so much. Exposed cast iron in a crawlspace is the cheap end. A line below a slab, or wrapped inside finished walls, sits at the expensive end, because concrete has to be cut and walls opened and rebuilt. Add permit fees, inspection and patching, which one guide budgets at around $500 for the permit on a 60-foot job. Those numbers come from national guides and do not substitute for a quote on your house. Supply lines are priced apart, in the cost to repipe a home; ask any plumber for a written quote that itemizes every section of pipe.

Is a permit required to repipe a house?

Usually yes. The City of Pasadena's exemption list says stopping leaks in drain, water, waste or vent pipe does not need a plumbing permit, but if a concealed pipe is defective and must be removed and replaced with new material, that counts as new work needing a permit and inspection.

So patching a leak is one thing and replacing a run is another. A repipe or drain replacement is permitted work in Pasadena, and the plumber normally gets the permit at the city's Permit Center and books the inspection. Neighboring cities, such as Arcadia and Alhambra, each keep a building department of their own, so the counter and fees differ. Confirm that whoever quotes holds a California contractor license (the state board's site has a lookup) and ask who owns the permit. A quote that skips it is a warning sign, as unpermitted work can cause trouble with an insurer or at resale.

What is the timeline for a repipe?

Expect several days for most drain or supply replacements, and a week or longer for a whole house once drywall and finishing are counted. Guides put many PEX supply repipes at one to four days of plumbing plus patching time. Drain work depends mostly on access and concrete.

A run exposed in a crawlspace can wrap up in a day or two. Under a slab the sequence is slower: break the concrete, replace the pipe, pass inspection, pour, then let it cure before flooring returns. The house may be without water or without working drains for much of each day, so you need a plan for toilets, showers and cooking. Ask for a day-by-day schedule that shows when water is off. Supply-pipe timing is covered in why repipe a house.

Is cast iron pipe for sale, and should I buy it?

Plumbing supply houses and some salvage yards stock cast iron pipe and fittings. We do not sell pipe; we arrange a plumber for the job. Plastic is the usual replacement for repairs, since it costs less, weighs less, resists corrosion and is easier to work with.

Cast iron still has a place: it is quieter than plastic when waste flows through a wall, and some builders and designers specify it for that reason. If you are matching existing pipe in a short repair, a plumber can use no-hub couplings to connect plastic to cast iron. Buying salvaged old pipe for a drain is risky because you cannot see inside it. Leave material choices to the plumber's written scope, and ask for the pipe type on the quote. Related cost guidance lives in our page on repiping with PEX, which covers supply lines.