Galvanized steel was first developed in the early 1800s, but it didn’t become popular until the 1850s and 1860s. It’s manufactured by coating steel with liquid zinc, which provides a barrier against corrosion and extends the useful life of the pipes. Because of its corrosion resistant properties and improved health safety, galvanized pipe was used as a replacement for lead pipes until the 1970s, when copper pipe became more popular, likely due to the corrosion problems galvanized steel suffers as it ages. Copper was then dethroned by plastic pipes like CPVC and PEX at the turn of the century. Today we usually only see galvanized used for repairs of existing pipe and on water heaters. It is still allowed for new installations as approved according to the 2017 Idaho State Plumbing Code section 604.
When galvanized steel plumbing pipes are used for water supply lines, the reaction between the zinc coating and the minerals in the water forms scale, which can dramatically reduce the expected lifespan.
Galvanized steel is also prone to scale build-up when it’s used for plumbing pipes. The zinc coating, whether pure or impure, interacts with the chemicals and minerals present in the tap water. This interaction creates a layer of scale that becomes thicker with time and reduces water pressure and water flow. This can become severe enough that it completely seals the inside of the pipe, preventing water from reaching the water fixtures.
- Internal rusting. Although the zinc barrier in galvanized pipes does prevent rusting for a certain amount of time, it eventually wears out. When this happens, your pipes begin to corrode from the inside out, which can eventually lead to a leak or a burst pipe.
- Unstable joints. The threaded joints that connect galvanized pipes are often unstable and prone to leaks and rusting. Often the threaded joints wear at the zinc coating of the pipes, which can quickly expose the metal underneath and cause corrosion.
The level at which galvanized pipes resist corrosion depends mainly on several factors, including the kind of zinc coating used, how thick the coat is, and the type of environment the pipes are exposed to. According to a report by the U.S. General Services Administration, the coating on galvanized iron and steel can be corroded by acids and strong alkalis and is very sensitive to sulfur acids created by hydrogen sulfide and pollution in urban areas
Most of our builders prefer to use galvanized piping for the water heaters due to several factors. It’s readily available and cheaper than brass or steel. Since we plumb thousands of houses, the price for galvanized is considerably cheaper due to the bulk pricing.
Most of the time the galvanized fittings will last a very long time but every fitting isn’t exactly the same quality as the last one nor is the water quality the same everywhere which affects the galvanized pipe and fittings. We have heard of other plumbing companies go out to older houses (1 year+) where there is a leak on the galvanized fitting and they tell the home owner that we didn’t install it correctly or it’s missing a dielectric fitting on the stainless-steel flex connector. We currently use 2 brands of flex connectors. One for the hot side and one for the cold side. The flex connector on the hot side the dielectric fitting is clearly visible. On the cold side the dielectric fitting is inside the flex line and nut and isn’t visible. We plumb every house to code so if another plumber is saying something isn’t installed correctly, I would question their work and knowledge.
Here is an example of a galvanized fitting that failed
You can see exactly where it failed after we removed the flex connector. The top part of the nipple should not have those 2 gouges at the ends. That is the source of the leak.