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Galvanized iron water lines were an acceptable building material at one time, perhaps a hundred years ago. The plumber that installed those lines could have used threaded brass pipes and fittings, but those materials were more expensive. If you have these pipes in your home and you are having water pressure problems in you home, your pipes have reached the end of their useful life span and must be replaced.
As galvanized iron water lines age the interior of the pipes gets clogged up with mineral deposits. Hot water temperatures seemingly accelerate the growth of these deposits. The mineral buildup does not affect the water quality, but it does have an impact on the quantity of water that the pipes can deliver. This build up can get so bad that it can virtually completely clog up a pipe.
Cutting copper tubing and soldering is not quite as challenging as you might think. You can now purchase cool copper fittings that already have lead-free solder built-in to the fitting. You simply clean the ends of the cut tubing with an abrasive cloth then clean the inside of the special fittings with a round wire brush. Apply a thin coat of soldering flux to clean the surfaces. After inserting the tubing into the fitting, you simply apply heat from a torch for a few seconds and you will see the solder appear at the tip of the fitting. This will show you that the solder joint is complete.
There are a few tricks you need to learn if you use traditional solder. The easiest thing to do is to buy an inexpensive propane torch kit, a small tubing cutter and the soldering supplies that you need. Make sure to purchase lead-free solder. Practice soldering a few joints before trying to solder the real thing. It shouldn’t take long for you to master this procedure.
You may want to use another piping material if copper seems too difficult. Plastic CPVC piping and fittings are approved by most plumbing codes in the U.S. This plastic piping is welded together using special primers and cements. You should follow the directions listed on the labels of these chemicals because the misuse of them can cause problems with the taste of the water if excess cement gets inside the pipes as you work.
CPVC piping has a very high expansion / contraction coefficient. This piping grows significantly when hot water flows through it. The growth can be almost 5 inches for every 100 feet of piping if the temperature of the water rises100F. Water temperature in regular household pipes will rarely raise to100F. But even if the temperature goes up just 50F, the pipes can expand and will cause all sorts of noise. If you use CPVC, make sure the pipes are not tightly clamped down and that they pass through large enough holes in wood framing so they do not bind.
Don’t even think about cleaning out old galvanized water lines. It is impractical and you will probably ruin the piping trying to take it apart. The old threaded joints might actually be near the point of rusting through and rotating them with a pipe wrench could break the pipe.
Galvanized iron water lines are easy to identify. The outer diameter of the pipe is usually 7/8 inch. It is grey piping it has never been painted. Where a pipe enters a fitting, you should see threads on the end of the pipe like you would on a standard threaded screw or bolt. Be careful. It is easy to confuse a threaded galvanized water line with a threaded black iron natural gas pipe. Never cut into a piping system unless you know for sure what is in the pipes.
You should never mix and match metallic materials. Copper adapters that make transitions between iron and copper pipes can cause a corrosive chemical reaction that causes the galvanized pipe to begin to rust and break down. When the corrosion gets bad enough, a leak will develop.