A weighted average

Over the wetted surfaces

On this page15

The measure Weighted average is the operative phrase And the weighting is by wetted surface area Which means geometry is part of the compliance question A small high-lead part can sit inside a compliant assembly And a large one cannot The wetted surface is the subject rather than the part So an o ring is mostly not in the calculation Which is a real distinction for several of this group's articles And solder is outside this half of the definition entirely No computation is performed here Nor is any wetted area established What the definition gives you is the shape of the question And that is worth knowing before reading any product claim References

A small part contributes a small share.

The measure

Not more than a weighted average of 0.25 percent lead when used with respect to the wetted surfaces of pipes, pipe fittings, plumbing fittings and fixtures.

Weighted average is the operative phrase

So the figure applies to an assembly as a whole rather than to each component in it.

And the weighting is by wetted surface area

Each component's lead content counts in proportion to its share of the wetted surface.

Which means geometry is part of the compliance question

Two assemblies with identical components in different proportions produce different weighted averages.

A small high-lead part can sit inside a compliant assembly

Because a small wetted area contributes a small share, and the average can absorb it.

And a large one cannot

Which is the same arithmetic run the other way, and it is why the component list alone does not answer the question.

The wetted surface is the subject rather than the part

A fitting's outside is not a wetted surface and does not count toward anything.

So an o ring is mostly not in the calculation

Its total surface is large relative to the thin band actually in the water path, and only that band counts.

Which is a real distinction for several of this group's articles

A compression ferrule, a tank bolt and teflon tape are all partly wetted, and only the wetted part enters the average.

And solder is outside this half of the definition entirely

It has its own flat 0.2 percent limit rather than a share of the weighted average.

No computation is performed here

A weighted average is computed for a particular assembly with particular geometry, and nothing on these pages does that for anything.

Nor is any wetted area established

Which of an article's surfaces is wetted depends on how it is installed, and that is not determined here either.

What the definition gives you is the shape of the question

Which surfaces touch water, what each contributes, and whether the area-weighted figure clears 0.25 percent.

And that is worth knowing before reading any product claim

Because a claim about a component and a claim about an assembly are different claims.

References

42 U.S.C. 300g-6(d) applies its 0.25 percent figure as a weighted average with respect to the wetted surfaces of pipes, pipe fittings, plumbing fittings and fixtures. So the measure is area-weighted across the surfaces in contact with water rather than applied to each component or to the mass of an assembly. No computation is performed on these pages for any assembly.

42 U.S.C. 300g-6(d), the definition of lead free. For solder and flux, "not containing more than 0.2 percent lead". For pipes and fittings, "not more than a weighted average of 0.25 percent lead when used with respect to the wetted surfaces of pipes, pipe fittings, plumbing fittings, and fixtures." This is a definition from the Safe Drinking Water Act; nothing on these pages describes what the Act prohibits, where it applies, the exemptions, the certification or the effective dates, or determines whether any article is lead free. law.cornell.edu

Written from 42 U.S.C. 300g-6(d) and from the catalog as it stood on 19 October 2026. That is a definition from the Safe Drinking Water Act and nothing here describes what the Act prohibits, where it applies, the exemptions, the certification or the effective dates, or determines whether any article is lead free. A weighted average over wetted surfaces is computed for a particular assembly and no computation is performed here. This shelf is shared identically by nine groups and the sewing notions property enumerates the inventory.