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Ten articles, and the water decides

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Faucet aerator Valve seat O ring Which is the interesting case for an area-weighted measure Supply washer and hose washer Compression ferrule Tank bolt Teflon tape Pipe clip and push fit clip So two of the ten are outside the measure And they sit in identical jars on an identical shelf Which is the honest limit of a container catalog here Nothing here determines which articles are wetted surfaces References

A faucet aerator is entirely wetted. A pipe clip is not wetted at all.

Faucet aerator

Water passes through it in its entirety. Essentially all of its surface is a wetted surface, which puts it at the heart of the measure.

Valve seat

The sealing face inside a valve, permanently in contact with water. Small in area and continuously wetted.

O ring

Which seals a joint and sits in the water path. A small torus, and its wetted area is a thin band of its surface.

Which is the interesting case for an area-weighted measure

An o ring has a large total surface and a small wetted one, and only the wetted part counts.

Supply washer and hose washer

Both sealing faces in a water path. The same geometry question as the o ring and the same answer.

Compression ferrule

Which is deformed onto a tube and seals against water. Partly wetted, and the wetted part is the inside.

Tank bolt

Which passes through a cistern wall and is submerged on one side. A genuinely partial case.

Teflon tape

Wrapped on a thread and compressed into a joint. Wetted where the joint is wetted, which is a thin interface.

Pipe clip and push fit clip

Neither touches water. A clip holds a pipe to a wall and a push fit clip retains a fitting from outside.

So two of the ten are outside the measure

Which is a clean division and it is about function rather than about the article being small or metallic.

And they sit in identical jars on an identical shelf

251 containers shared by nine groups, and nothing about the container distinguishes a wetted part from a dry one.

Which is the honest limit of a container catalog here

We can keep ten kinds of small part sorted and dry. The water contact question is about the part.

Nothing here determines which articles are wetted surfaces

The descriptions above are the ordinary function of each article and not a determination for any product.

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.