by A. Smith

Created on: December 24, 2011   Last Updated: December 25, 2011

Household pipes can be made of many different substances. Two of the most common are brass and copper. It is easy to tell these two metals apart.

In the Universal Numbering System, the UNS numbers for all copper and copper alloys begin with the letter C. Copper pipe made from bright annealed copper has UNS numbers C10200, 10300, and 10800. Basic copper sheetshave the UNS number C11000. Copper alloys, including different types of brass, has its own

UNS number.

In the absence of UNS numbers, other methods can be used to tell copper and brass apart. Visual inspection can tell them apart in most cases.

Copper is a metallic element which is the same color as a penny. When untarnished, copper is orange-brown, with a low sheen. Tarnished copper is moss green. This color is called verdigris. Copper piping is usually not in contact with sulfur in city air and does not tarnish. The color of untarnished copper is sometimes described as warm.

Brass is an alloy made of copper and zinc which is yellow or brownish-yellow, with a very high sheen. It looks similar to unalloyed gold, and is not orange in color like pure untarnished copper. However, brass can tarnish, unlike gold. Tarnished brass is dull brown or black. The color of untarnished brass is sometimes described as cold.

Brass is harder than copper. This is the reason for making a copper alloy, which will hold up better to external pressures better than the unalloyed metal. On the other hand, brass is not as flexible or strong as copper, and is subject to corrosion cracking.

Another way to tell the difference between brass and copper pipes is to tap the pipes gently with a metal hammer. Brass is harder and has a clear sound. Copper is softer and has a smoother sound.

Copper is never ferromagnetic. Most types of brass are not ferromagnetic in normal magnetic fields. Watch out for copper-colored steel, which looks superficially like copper and is strongly ferromagnetic.

Some brasses contain as much as 2% lead. This can leach out of the piping because its melting point is lower than other brass alloy components, so it is disproportionately represented in the wetted surfaces of pipes. Some new requirements for low-lead plumbing products take this difference in lead distribution into account by measuring the percentage in wetted surfaces and not the percentage by dry weight.

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