The traditional material for faucets is brass.

Brass is prized for faucets because it is very resistant to corrosion, has a relatively low melting point — making it easy to cast — is soft enough to machine with little effort yet hardy enough to endure the rigors of life as a faucet, takes finishes such as chrome plating very well, and is easily recycled. About 80% of the brass used in new faucets was previously used to make something else.

Common yellow or "alpha" brass is about 60% copper and 30% zinc the rest being small amounts of other metals to give the brass specific properties. A little antimony or tin might be added to retard a form of corrosion known as dezincification which can weaken brass over time. A pinch of iron or manganese makes brass harder and nickel refines the grain structure improving strength and corrosion resistance.

Aluminum may be added to make the brass stronger and more corrosion resistant. Admiralty and naval brasses used in salt-rich maritime environments contain a relatively high proportion of aluminum.

The copper in brass is anti-microbial — it kills germs, a fact that has been known since the rise of the Pharaohs, but how it does so has only recently been uncovered.  Many fungi (mold and mildew) and most bacteria cannot survive in the presence of copper. In tests on colonies of E. Coli bacteria conducted by the EPA, 99.9% of the colony was killed after two hours of exposure to brass.

Lead is added to make brass more malleable, less brittle, and easier to form. In faucet brass, however, lead is dangerous to human health, and especially dangerous to children because it can lech into drinking water.

According to the Environmental Protection Agency lead can cause slowed growth, learning problems, hearing loss, anemia, hyperactivity, and behavior issues.

Before 2014, a faucet could contain as much as 8% lead and still call itself lead-free. Now the maximum lead content in a faucet is 0.25% (1/4 of 1%), basically just a bare trace of lead. To ensure the absence of lead in the brass inside a faucet that is in contact with the water passing through the faucet, the faucet must be tested in a laboratory and certified lead-free. If it is not certified, it cannot be legally installed in a drinking water system.

To produce a lead-free brass, the lead is replaced with bismuth or silicon to provide the needed malleability without the toxicity. Bismuth is similar to lead – right next to lead on the periodic table of elements – but it is not harmful to humans. Bismuth, however, is expensive. It is 300 times rarer than lead, even rarer than silver, which is the reason that bismuth-brass alloys are considerably more expensive than leaded brass.

Bismuth has several other problems. It is, unlike lead, a brittle metal, and requires a more precise casting process to preserve the ductility of brass. The result of improper casting is illustrated by a 2012 recall of 63,000bizmuth-brass ball valves made in China for use in natural gas pipelines. They were much too brittle resulting in cracks and dangerous valve failures. Bismuth is also an environmental issue. Brass alloyed with bismuth cannot be easily recycled with non-bismuth brass and must be kept separate to avoid cross-contamination of the materials.

Silicon has somewhat similar recycling issues, but not as severe. Some alloys can be recycled with ordinary brass. Its chief advantage is that it is plentiful and, therefore, much less expensive than bismuth. Silicon-brass is also considered a high-strength brass. The silicon increase resistance to wear and corrosion. Its disadvantages are that it requires a higher casting temperature than ordinary brass and its hardness makes it much more difficult to machine. Nonetheless, it is increasingly popular among faucet manufacturers due to its relatively low price tag. One alloy, Eco-brass® C69300, is especially formulated for plumbing fixtures.