Understanding galvanized steel plumbing

If your home is more than 30 years old, it’s likely your water pipes are made from galvanized steel. For the avid DIYer living in an older home, a working knowledge of galvanized steel is important in order to properly repair or replace pipes and fittings.

To tell if your plumbing system includes galvanized steel pipes, find where the pipes enter your home from the supply lines and scratch one. If it is made from galvanized steel, the scratched area will reveal a pipe with a blue-grey colour and have threads. [Photo Credit: istock.com/tomeyk]

• Galvanized steel is a type of steel pipe or fitting that has been coated, or galvanized, with a layer of zinc.
• Steel itself is a composite material comprising a number of metals, including iron and carbon. Sometimes, galvanized steel pipes are referred to as “galvanized iron” pipes.
• The use of galvanized steel pipes for carrying water was very popular in the 20th century, when it was discovered that that the layer of zinc helped increase the lifespan of the pipes by preventing corrosion.
• We now realize that galvanized steel has a tendency to react to the minerals in the water it carries, resulting in scale.
• Because galvanized steel pipes corrode from the inside, the build up of scale can lead to a lower water pressure.

• In older homes, galvanized steel pipes and fittings are likely signs that the original plumbing is still in place.
• Depending on the level of corrosion, it may be time to consider switching galvanized steel pipes for newer materials, such as PVC (poly vinyl chloride) or PEX (cross-linked polyethylene).
• In newer plumbing systems, galvanized pipe is most commonly used for drains and vent pipes or for replacing existing pipes.
• Galvanized nipples are still used for penetrating fire-rated walls for sinks and urinals in commercial buildings.
• Galvanized steel pipes should only be used for water supply pipes or drains.
• Galvanized steel is unsuitable for carrying gas, as the zinc tends to flake and could lead to a gas blockage.

Good to know!

If your home is on a well system rather than city utilities, have the water tested. A pH water reading of lower than 6.5 is hard on copper, so galvanized plumbing may be a good option. Check with a professional plumber and your local municipality.

•   If you decide to repair a leak in your galvanized plumbing rather than replace it, often the part you need is now made from copper.
•   Copper combined with galvanized steel can very quickly lead to corrosion. To avoid this, use a dielectric union.
•  A dielectric union separates the copper from the galvanized steel pipe; this is typically done by inserting a rubber washer between the two metals.

Good to know!

Be aware that if you have one clogged pipe and a leaking joint, it’s possible that it’s time to replace the entire system. However, if it’s just one leak that’s concerning you, the dielectric union will often repair the pipe for a long period of time.

Pros:

• Water pipes made from galvanized steel have been coated in a layer of zinc, and have a high resistance to corrosion.
• Compared to copper piping, galvanized steel pipes are relatively inexpensive.

Cons:

• Galvanized steel pipe is more expensive than PVC.
• Pipes made from galvanized steel are significantly heavier than modern plastic material, which makes it difficult to work with.
• The zinc coating causes internal rusting, which can lead to reduced water pressure over time as the galvanized pipes clog.
• Corroded galvanized pipes can result in lead being released into the tap water.

Good to know!

Galvanized steel piping has a life span of approximately 40 years. If your home was built prior to the 1970s, check with a professional plumber to see if your water pipes should be replaced.

There’s no reason to panic if you discover your home has galvanized steel pipes in the plumbing system. Nor should the presence of galvanized steel pipes deter you from buying that dream house you’ve set your heart on. Just be aware that the limited lifespan of galvanized steel plumbing means you may encounter leaks that need fixing and, at some point in the not-so-distant future, you may need to replace the pipes.