Galvanized steel supply pipe is the plumbing of houses built from the 1930s into the 1960s, and it lingered later in some markets. It is steel with a zinc coating. The zinc goes first. Then the steel rusts from the inside, the bore closes, and pressure drops at the fixture farthest from the main. By the time the water runs orange, you are not looking at a dirty aerator. You are looking at a pipe that is mostly rust.

This is supply piping. It is not polybutylene, which is gray plastic from the late 1970s to the mid-1990s and fails by splitting. It is not cast iron drains, which carry waste. A house can have galvanized supply and cast iron drains at the same time. Budget them separately.

What it is

Joints are threaded. A magnet sticks to the pipe. Where someone has already repaired a leak, you will see a short run of copper or PEX spliced in with a dielectric union, or, worse, without one, which starts a new corrosion cell. "Partial repipe" in the remarks usually means the accessible horizontal runs were replaced and the stacks inside walls were left.

How to spot it in the listing

Age is the first filter. A 1952 house with no plumbing comment is more suspicious than a 1952 house that says "repiped in 2016" and names the material. Photos of unfinished basements, utility rooms, and water heaters show the pipe if the photographer was not trying to hide it. Gray-silver threaded pipe, often with crusty joints, is galvanized. Bright copper and colored PEX are not.

Low-pressure complaints sometimes leak into old listing descriptions if the house was on the market before. Read the previous remarks, not just this week's. Property research beyond the listing is how you find the prior text and the permit for a repipe that may or may not exist.

How to spot it at the showing

Run the highest fixture and the shower at the same time. Galvanized that has closed up cannot serve both. Look at the pipe at the water heater and under the kitchen sink. Scratch a dull spot: zinc is dull gray, copper is copper. Ask to see the main shutoff. If the first ten feet are new PEX and then the pipe disappears into a wall as threaded steel, you have a partial repipe.

Rusty water on first draw that clears is often the water heater, not the house. Rusty water that continues, or rust only on the hot side throughout the house, can be either. Do not diagnose from one glass.

The real risk

The pipes clog, then they leak, usually at a thread. Leaks inside walls show up as stains, soft drywall, and sometimes mold. Water pressure that is already poor does not get better. Lead can be a secondary issue: some old galvanized picked up lead from upstream lead service lines or from leaded fittings. That is a water test, not a guess. See lead paint for the paint side of pre-1978 houses. The pipe question is separate.

Insurance and lending

Insurers care more about active leaks and about polybutylene than about quiet galvanized, but a house with a history of water claims will get surcharged or declined regardless of pipe brand. Lenders on conventional loans rarely require a repipe. FHA appraisers can require repair of active leaks. A slow seep at a galvanized joint that the seller "has been watching" is an active leak. Some local insurers in older cities have started asking pipe material on older homes. Get the quote before you waive inspection.

Typical cost ranges

Typical ranges, not quotes. A whole-house supply repipe to PEX or copper is commonly $5,000 to $15,000 for a one-story house with a basement or crawlspace, and $12,000 to $25,000 or more when the house is slab, multi-story, or plaster. Drywall and paint are often extra or buried in the high end. Replacing only the visible basement runs is cheaper and leaves the problem in the walls. A spot repair at one leaking joint is a few hundred dollars and is not a repipe.

Pass, negotiate, or investigate

Investigate with a plumber who will look at the pipe, not just the pressure. Ask what is galvanized, what is already new, and whether the service from the street is lead, galvanized, or copper. Negotiate a credit against a written repipe when pressure is already failing or the pipe is wet. A credit is cleaner than a seller-arranged plumber in a hurry. Pass when the seller's "plumbing updated" has no invoice, the basement pipe is crusted, two fixtures cannot run together, and you are being asked to waive inspection on a house you cannot insure after the first claim. The inspection checklist has the fixture test. Use it. If the plumber's camera or the pressure test says the hidden runs are already closed up, price the whole repipe, not the visible basement.

Galvanized Steel Pipes: When the Water Pressure Is the Inspection