Galvanized steel pipe

Entry in Metal pipe · Updated October 29, 2026 · Written by the Know Your Pipes editors from the sources listed under References

Galvanized pipe is steel water pipe that has been dipped in molten zinc to slow rusting, and it was used in US homes from about the 1880s to the 1960s^[1]. Galvanized steel pipe was developed as an alternative to lead pipe, and a house may have it alongside copper, lead or PEX in the same system^[1].

1 Identification

New galvanized pipe is gray to silver, while old pipe may be dark brown, gray or nearly black on the surface^[2]. A magnet sticks firmly to it, the surface resists scratching, and the ends of each length are threaded into fittings^[2]. Those three checks separate it from copper and from soft lead pipe; identifying your pipes walks through all common materials.

Table source: EPA identification guidance^[2].

Steel gas pipe looks similar but has no zinc coating; see black steel gas pipe. Galvanized pipe is not used as a stand-in for black pipe on gas lines where codes or the gas utility prohibit it, so the local code governs.

2 Corrosion and low pressure

Over years of contact with minerals in the water, the zinc layer wears away and the steel begins to corrode from the inside^[1]. Rust and scale build up and narrow the bore, which restricts flow and lowers water pressure; because some runs corrode faster than others, pressure can differ from one fixture to the next^[1]. Iron released by the corrosion can turn water brown and stain sinks, and in time the pipe rusts through and leaks^[1].

Joining different metals, such as iron or steel with copper or brass, creates the conditions for galvanic corrosion^[4]. A dielectric union is the usual separator; see also threaded pipe joints for how the fittings seal.

3 Lead in galvanized pipe

EPA notes that the zinc layer on galvanized pipe may contain traces of lead, and that the corrosion scale inside the pipe can collect lead when a lead source is upstream^[2]. Researchers cited by EPA found that lead released from lead service lines was adsorbed onto galvanized pipe in homes, and that iron-rich scale remained a source of lead for more than four years after the lead lines were removed^[5].

For that reason, EPA's Lead and Copper Rule Improvements treat some galvanized service lines as "galvanized requiring replacement" (GRR): any galvanized line now or previously fed through a lead service line, any galvanized line fed through a line of unknown material, and any line the water system cannot prove was never fed through lead^[3]. Water systems must replace GRR lines under their control, together with lead lines, generally within 10 years^[3].

4 Replacement

A city water utility advising homeowners describes galvanized pipe still in service as likely to be near the end of its life, and names copper or PEX as replacement choices where there is low pressure, rust or leaks^[1]. Options and code rules are compared in which pipe for which job and PEX pipe; repiping is work for a licensed plumber under a permit.