Galvanized steel pipes were used for potable water distribution in single family homes as well as in apartment and condominium buildings until about the 1960’s. It was the standard water pipe material; everybody used it pretty much exclusively. They’re joined together with threaded fittings. Galvanized steel pipes are just steel with a zinc coating for protection. The zinc coating is the “galvanized” part. But over time the zinc coating wears away, and you’re down to bare steel. And of course steel rusts.
The pipes will rust on the inside (obviously, since that’s where the water is), and this corrosion tends to clog and choke down the inside diameter of the pipe. With the smaller inside diameter you’ll get less water flow and lower pressure at your fixtures. Hot water pipes tend to corrode more quickly because the heat accelerates the corrosion process.
The inside of this galvanized steel water pipe is corroded.
Reduced water flow and pressure is the predominant problem, but the pipes can also rust through and start to leak. And of course leaking water pipes can cause a tremendous amount of damage, especially if the leak is inside a wall. The threads typically rust first, so this is where you want to start looking if you’re going to examine your galvanized pipes.
This pipe rusted all the way through and had to be repaired with a clamp.
This pipe elbow is rusted through and leaking, just a little bit. The leak will just get worse and worse, until . . . disaster.
The life expectancy of galvanized pipes varies – a lot. I’ve seen galvanized steel water pipes in houses from the 1920’s and even the 1910’s that are in surprisingly good condition. The water flow through these pipes is good, and there’s little sign of rusting. Folks knew how to make pipes back then. Still, these pipes are very old, certainly have some rust, and are probably near the end of their expected life. And I’ve seen galvanized pipes from this era that are badly rusted and provide terrible pressure. You should plan on needing to replace all galvanized pipes in the near future. Also, most houses of this vintage have had all (or almost all) of their galvanized pipes replaced already. So if your house still has galvanized pipes then it’s behind the curve in terms of being updated like it needs to be – something to keep in mind when making an offer.
On the other hand, some Chicago buildings from the 1950’s and 1960’s have already had to replace their galvanized pipes. It seems that cheaper production methods and materials created an inferior product that quickly deteriorated. And I’ve seen pretty much everything between these two extremes. Either way, if you have galvanized steel water pipe in your house it’s probably near the end of its expected lifespan, and you should plan on needing to replace it in the near future.
Keep in mind that there’s no way to know for sure when galvanized pipes will fail. You can have a team of scientists and engineers inside your house for a month, and you still can’t know. You just have to follow the basic guidelines.
In Chicagoland, almost all jurisdictions require new water pipes to be copper. But some cities will allow PEX (cross linked polyethylene) water pipes and some allow CPVC. PEX is used almost exclusively throughout much of the rest of the country, so it has a long record of success, and the problems with fittings (the weak link in any water system) have been worked out by others.