There are two different waters here, and the answer is different for each. The tap water comes from groundwater wells, and the Town’s 2025 report says it met every U.S. EPA and State drinking water standard. The Delta water behind the houses has had harmful algal bloom advisories, including a state “danger” advisory in July 2024 and a “caution” advisory for Willow Lake posted on the Town’s site as of September 25, 2026.
We’re not doctors, and this isn’t health advice. It’s where the official information lives, so you can check it yourself before you buy.
Where does Discovery Bay tap water come from?
From wells, not the lagoons. The Town’s report says its drinking water comes from groundwater wells in the San Joaquin Valley Basin: five sources (Wells 1B, 2, 4A, 6 and 7), treated at the Newport Drive and Willow Lake treatment plants (Town of Discovery Bay, 2025 Annual Water Quality Report, PWS ID 0710009).
Veolia Water operates and maintains the Town’s water facilities under contract. The Town’s number is (925) 634-1131, and Veolia’s after-hours line for leaks is (925) 634-8818 (Town of Discovery Bay, Water Services page, checked September 25, 2026).
What does the 2025 water quality report say?
It says the water met all federal and state health standards in 2025 and that the system “has never violated a maximum contaminant level” (Town of Discovery Bay, 2025 Annual Water Quality Report, covering January 1 to December 31, 2025). A few of the numbers people ask about, all from that report:
| What was tested | Result | The limit |
|---|---|---|
| Arsenic, 2024 samples | Average 2 ug/L, range not detected to 6 | 10 ug/L (MCL) |
| Lead, 2024, 30 home taps | 90th percentile 2 ug/L, 0 sites over | 15 ug/L (action level) |
| PFAS, 2024 federal UCMR5 sampling | Not detected or well below reporting limits | Reported to state and federal regulators |
Read the whole report yourself. It’s on the Town’s website under Water Services. If you have a question about your own tap or plumbing, call the Town and ask for Veolia. If you have a health question, ask your doctor.
What happened with the algae in 2024?
The state posted a “danger” advisory. On July 9, 2024, the State Water Resources Control Board and the Central Valley Regional Water Quality Control Board said water samples from multiple Discovery Bay locations confirmed harmful algal blooms. The advisory urged people to avoid swimming, boating and other water activities and to keep pets out of the water until further notice (State Water Resources Control Board, “Harmful algal bloom confirmed at Discovery Bay,” July 9, 2024, checked September 25, 2026).
The release says the Town, working with Contra Costa Environmental Health, posted advisory signs. Read the full release at waterboards.ca.gov for the details.
Is there an algae advisory in Discovery Bay right now?
As of September 25, 2026, the Town’s Harmful Algal Bloom page shows a “caution” advisory for Willow Lake, issued by the state because of visual signs of a bloom (Town of Discovery Bay, Harmful Algal Bloom page, checked September 25, 2026). The Town lists the signs to look for: discolored water, surface scum or a spilled-paint look.
Advisories change with the weather and the season. Check before you go in the water, every time:
- The state’s HAB portal at mywaterquality.ca.gov/habs, which has a map of reported blooms.
- The Town’s homepage and HAB page at todb.ca.gov.
- Posted signs at the water’s edge.
Seen something that looks like a bloom? The state takes reports at mywaterquality.ca.gov/habs/bloom-report.
Who is working on the algae problem?
A few agencies, each with a piece of it. Reclamation District 800 manages water circulation in the lakes and lagoons and posts notices about Willow Lake algae and aquatic weed treatment (RD 800 home page, checked September 25, 2026). Its July 9, 2026 board minutes report that five algaecide treatments had been applied to Willow Lake, with more planned for September and November (RD 800, board minutes, July 9, 2026). Its new Maintenance and Capital Assessment, which the board approved on November 6, 2025, lists $3 million for Willow Lake water quality improvements among its capital plans (RD 800, board minutes, November 6, 2025, and community meeting presentation, August 28, 2025).
The state Water Boards investigate and post advisories. Contra Costa Environmental Health handles local health signage. For what an advisory means for you or your pets, talk to your doctor, your vet or Contra Costa Health.
Should algae change whether I buy a waterfront home here?
That’s your call, and it depends on how you plan to use the water. Here’s what we’d do before you write an offer:
- Look at the history. Search the state HAB map for Discovery Bay and read how often advisories were posted.
- Visit in summer too. The 2024 danger advisory came in July. See the water behind the house in the warm months, not just in April.
- Ask the seller. Ask about advisories, weed problems and anything they’ve noticed on their stretch of water.
- Know the difference. An algae advisory on the lagoon isn’t about your kitchen tap. Those are separate systems with separate reports.
Questions people also ask
Is Discovery Bay tap water from the Delta?
No. The Town of Discovery Bay’s 2025 Annual Water Quality Report says its drinking water comes from groundwater wells in the San Joaquin Valley Basin, treated at the Newport Drive and Willow Lake plants. The same report says the water met all U.S. EPA and State standards in 2025. Questions about your tap go to the Town at (925) 634-1131.
Can I swim in Discovery Bay?
Check the current advisory first, every time. On July 9, 2024 the state posted a danger advisory urging people to avoid swimming and keep pets out of the water. As of September 25, 2026, the Town’s site shows a caution advisory for Willow Lake. See the state HAB portal and the Town’s page, and ask your doctor about health questions.
Where do I check for algae advisories in Discovery Bay?
Use the state’s Harmful Algal Blooms portal at mywaterquality.ca.gov/habs, which maps reported blooms, and the Town of Discovery Bay’s Harmful Algal Bloom page at todb.ca.gov. Look for posted signs at the water too. You can report a suspected bloom through the state’s online form at mywaterquality.ca.gov/habs/bloom-report.
Is there lead in Discovery Bay water?
The Town’s 2025 water quality report shows lead sampling from 30 home taps in 2024, with a 90th percentile result of 2 ug/L and no sites over the 15 ug/L action level. Older plumbing inside a house can still matter, so ask the Town, which contracts with Veolia, about testing, and read the full report on the Town’s website.
Your next step
Looking at a home on the water? Send us the address. We’ll pull the advisory history for that stretch, the seller disclosures and recent sales on the same lagoon, so you can weigh it with real facts. Ask our team about a Discovery Bay home or call (510) 949-5525.
More on Discovery Bay: Is Discovery Bay a good place to live? · Things to do in Discovery Bay · What’s my home worth?
By Bill Davis, DRE #01880656, The Davis Team at eXp Realty, Discovery Bay, CA. Updated September 25, 2026.
Sources
- Town of Discovery Bay, 2025 Annual Water Quality Report, PWS ID 0710009: todb.ca.gov (checked September 25, 2026)
- Town of Discovery Bay, Water Services and Harmful Algal Bloom pages: todb.ca.gov (checked September 25, 2026)
- State Water Resources Control Board, “Harmful algal bloom confirmed at Discovery Bay; public urged to avoid water activities,” July 9, 2024: waterboards.ca.gov (checked September 25, 2026)
- California Water Quality Monitoring Council, Harmful Algal Blooms portal and bloom report form: mywaterquality.ca.gov/habs (checked September 25, 2026)
- Reclamation District 800, home page, board minutes of November 6, 2025 and July 9, 2026, and community meeting presentation of August 28, 2025: rd800.org (checked September 25, 2026)