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.

I’m Joe Kim, founder of Myriad Labs, a scientist, and a 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.

01 · The results

The results were reassuring.

The San Francisco tap-water samples performed as well as the premium bottled waters.

Illustrative kitchen scene showing a glass filled from the tap beside FIJI-style plastic and Evian-style glass water bottles.

02 · Your own tap

What could you learn about your own tap?

Seeing the results from my own home gave me the confidence to drink straight from the tap.

This five-page report turns real household test results into practical answers:

  • Drinking water: What was found and how the results compare with drinking-water benchmarks and bottled water.
  • Minerals: What’s in your water and how much it contributes to daily mineral intake.
  • Hardness and your home: What it means for scale, kettles, coffee makers, and other appliances.
  • Your action plan: Whether results suggest a need for targeted filtration, plumbing follow-up, or retesting.
  • The full results: Sample details and measurements for a closer look.

Real results from Joe’s San Francisco home · 5 pages

03 · Across the city

Bring that confidence to every San Francisco family.

Conceptual illustration of citywide water testing connecting a San Francisco home, school, café, park, and playground.

Seeing my own results gave me confidence to drink from the tap. We want every San Francisco family to have that same opportunity.

Our next step is regular testing in homes, schools, and local businesses, alongside more than 250 public water fountains in parks, playgrounds, and other public spaces. Clear reports and neighborhood comparisons would help residents understand the water they drink throughout their day.

Helping families choose tap water with confidence can reduce avoidable spending and single-use plastic waste.

04 · Actionable data

Confirm, investigate, act, and retest.

SFPUC protects San Francisco’s excellent water. Our program complements that work with testing at the taps where people drink it. If we find a concern, we confirm it, give the City or property owner clear evidence to guide action, and retest to check that it was resolved.

Use citywide results to locate concerns.

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.

A cluster of elevated results can help the City focus its investigation: verify the pipe connections, then compare upstream (U) and downstream (D) samples.

Find patterns within a building.

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 the shared floor branch.

When one floor stands out, samples before (A) and after (B) its supply connection can help a plumber narrow the search for the cause.

Our goal

Help every San Francisco resident enjoy water from Yosemite, straight from the tap, with confidence.