What percentage of lead is acceptable in lead free solder?

In plumbing, the term "lead-free solder" specifically refers to solder that meets regulatory standards for safe use in drinking water systems. According to the Safe Drinking Water Act's requirements, lead-free solder must contain no more than 0.2% lead by weight when used in the installation or repair of potable water systems.

Choosing the option indicating 0% lead aligns with the highest safety standards, emphasizing that no lead should be present in solder designated as lead-free. The principle behind lead-free solder is to protect public health by minimizing the risk of lead exposure from drinking water systems.

The other options presented suggest low percentages of lead that do not meet the regulatory definition of lead-free, which could pose health risks. Solder containing even a small amount of lead, such as 1% or 2%, would still be considered unsafe for potable water applications according to current guidelines. Thus, within the context of plumbing regulations and safety, the assertion that acceptable lead content is 0% is essential for ensuring the health and safety of drinking water infrastructure.