Myriad Labs · San Francisco Water Confidence Initiative

We tested San Francisco’s tap water.

Conceptual illustration blending a Yosemite-inspired reservoir landscape into a San Francisco kitchen tap filling a glass.

Why?

San Francisco’s water comes largely from Yosemite, and the City does excellent work protecting its quality. But knowing where our water comes from isn’t the same as knowing what reaches our own tap. That uncertainty can leave families paying twice: the utility bill, then bottled water and filters.

As a scientist and San Francisco parent, I wanted to see the evidence for myself. We started with a small pilot, testing water from public fountains and my own home for nanoplastics, metals, and minerals, alongside selected premium bottled waters.

The results were reassuring: the San Francisco tap-water samples performed as well as the premium bottled waters. Seeing the results from my own home gave me the confidence to drink straight from the tap.

Now we want more families to have that same opportunity: to understand their water, make informed choices, and have clear next steps if something needs attention.

Joe Kim, founder of Myriad Labs and San Francisco parent

01 · Explore the results

Water quality at our San Francisco sampling sites.

Hover over or tap a sample point to explore its results. The arrows on each scale show the bottled-water comparisons. These maps show the sites sampled in our pilot.

02 · Your own tap

What could you learn about your own tap?

This sample report turns one household’s results into everyday answers: what was found, how the water compares, what its minerals and hardness mean, and what to do next.

Sample household water report, page 1 of 5: Drinking-water metals screening and everyday questions
Sample household water report, page 2 of 5: Water profile, minerals and nutritional contribution
Sample household water report, page 3 of 5: Water comparisons
Sample household water report, page 4 of 5: Hardness and household use
Sample household water report, page 5 of 5: Sample details and supplemental results

03 · What comes next

Expand testing across San Francisco.

Our next step is to expand into homes, schools, and local businesses across San Francisco, alongside more than 250 public water fountains. Regular testing and clear reports would help residents understand the water they drink at home, work, school, and in public spaces, while complementing the City’s existing monitoring.

Illustration · simulated data

Use citywide results to locate concerns.

Illustrative sample points and pipe routes show how the system could work. They are not actual City infrastructure or pilot findings.

Example follow-up area U D

● Simulated sample ● Example requiring follow-up

Thick trunks → smaller branches → individual taps
Blue-gray: illustrative network · Amber: shared branch
U / D: proposed upstream / downstream samples
Amber square: junction to investigate

Find the shared supply path.

If nearby taps on one branch show elevated copper while taps on other branches do not, that shared path is a place to investigate.

After checking the actual pipe connections and flow, samples upstream (U) and downstream (D) help narrow down the source.

For the City: a clearer picture of where to investigate next.

Illustration · simulated building and results

Find patterns within a building.

A floor-by-floor view can help residents and property managers narrow down where follow-up testing is needed.

Illustrative condo building plumbing cross-sectionFour floors, three sampled apartments per floor. Simulated results on floor three need follow-up. Its shared horizontal branch is highlighted. A and B mark proposed samples on the riser before the connection and on the floor branch after it. This is hypothetical plumbing, not a diagnosed problem.Building supplyShared riserFl 4Unit 401Unit 402Unit 403Fl 3Unit 301Unit 302Unit 303Fl 2Unit 201Unit 202Unit 203Fl 1Unit 101Unit 102Unit 103ABAmber branch: investigate the shared floor supply

● Reassuring example result ● Follow-up needed
A: riser before the connection · B: floor branch after it

Check what the affected apartments share.

If one floor’s samples show elevated copper while other floors do not, check whether those apartments share a supply branch.

Compare samples before the connection (A), after it (B), and at the affected taps. The pattern guides investigation; it does not establish the cause.

For the property owner: evidence to help a plumber focus the inspection.

Confirm, investigate, act, and retest.

We would confirm unexpected findings, share the evidence with the City or property owner, and retest after action to check whether the concern was resolved.

Household reports

Give participating households understandable results that help them make informed water choices.

Neighborhood comparisons

Bring results together in a neighborhood map that reveals patterns while protecting household privacy.

Follow-up and retesting

Confirm water-quality concerns and share clear data with the City and property owners to guide follow-up, then retest.

Enjoy San Francisco’s water with confidence.

When the results are reassuring, residents can drink with confidence. When testing reveals a problem, we give the City and property owners clear data to address it, then test again to confirm the improvement.

Either way, the goal is the same: helping every San Francisco resident enjoy water from Yosemite, straight from their tap, with confidence.