Prior to around 1960, galvanized steel pipe was a popular alternative to lead pipe for home water supply lines. This type of steel pipe is coated in zinc to protect it from corrosion and rust. The problem is, over the years some galvanized steel pipes may start to rust from the inside out, which can cause reduced water pressure and the potential for flood-causing leaks or ruptures.
Today, most DIY work involving galvanized pipe is related to repairs of existing older pipes versus installation of totally new plumbing systems, which have shifted mostly to plastic piping or even copper.
Important note: If you plan to make repairs to existing galvanized steel pipes that incorporate plastic or copper piping, you should purchase specialized galvanized pipe fittings to prevent premature corrosion that can happen by joining different types of metal.
However, if you plan to repair galvanized pipes using similarly galvanized iron fittings, simply follow the steps below.
Connecting Non-Threaded Galvanized Pipe
Step 1: Measure
If you are connecting galvanized pipes that are not already threaded, you’ll need to use a galvanized iron coupling that creates a properly sealed joint. Failure to use the correct coupling can cause damaging leaks, mostly due to the rough edges most galvanized pipes have as a result of the zinc coating.
First, measure the diameter of each pipe with a tape measure. If they are the same diameter, you can go with a standard coupling. If they are different, you’ll need to purchase a stepped coupling that steps up in size to match the connecting pipe.
To properly measure the diameter of the pipe, remember that the diameter of the inside of the pipe is different than the outside. For example, even if the outside diameter of the galvanized steel pipe you’re working with measures ¾", you’ll need a coupling that matches the interior diameter where the pipe and the coupling meet. A pipe that has a ¾" outside diameter should have an interior diameter that measures ½", and that’s the coupling size you should purchase.
Step 2: Check the coating
As mentioned above, is the surface of the pipe rough? If it is, you’ll need to procure a specialized coupling that is designed for rough and uneven surfaces. (Ask the plumbing expert at your local hardware store.) A smooth surface means a standard coupling should work just fine.
Step 3: Prepare the pipe
Before joining, use a level to make sure the end of the unthreaded pipe is perfectly square. If it isn’t, you’ll need to use a saw to cut it to square and sand down the edges. Then, wipe the pipe with a water-based degreaser. Place the coupling up to the center of the pipe joint and mark a line on each end of the coupling using a grease pencil.
Step 4: Connect the pipes
Place one end of the non-threaded pipe into the coupling and align the end with the pencil line on the pipe. Do the same with the second pipe and be sure to center the coupling between the two lines. Then, tighten the fastening bolts so the coupling holds the pipes securely. If needed, a torque wrench can be used to evenly tighten the bolts.
Connecting Threaded Galvanized Pipe
If you are connecting threaded galvanized pipe, you’ll need to coat all of the threads with what’s known as pipe dope—a common thread lubricant and sealing compound—or wrap the threads with PTFE (short for polytetrafluoroethylene) plumber’s tape. This helps secure a water-tight connection.
After getting the connection hand-tight, use one pipe wrench to hold the pipe in place and the other to tighten the fitting.
Loosening Galvanized Pipe Fittings
If you want to loosen galvanized pipe fittings that have become corroded, you’ll need to use a loosening agent to help the cause. Start by turning off the water that flows to the section of pipe that you’re working on, and spray some penetrating oil where the threaded pipe connects with the fitting that is being removed.
Place one pipe wrench onto the lock nut and the other on the retaining nut. Loosen the connection by turning the nut counter-clockwise.
Then, hold the fitting securely with one of the pipe wrenches and use the other pipe wrench to turn the loose piece of pipe that is connected to the fitting. Turn the wrench on the loose pipe counter-clockwise and remove the galvanized fitting.
Next, move the wrench that was on the loose pipe to the pipe on the other side of the fitting you are removing. Again, turn the wrench counter-clockwise and the fitting should come free. If you need additional leverage, place a piece of pipe over the handle of the wrench and press downward.
Once you know how to join and loosen galvanized pipe fittings, you’ll be equipped to make the many necessary repairs in older homes. This can save you significant dollars during a renovation project by reducing the chances of having to fully replace all of the galvanized steel pipes with new plastic piping.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.