Water sommeliers take water tasting to the next level  

Members of the Flavor Profile Analysis Panel form an important part of our water quality control system. Meet some of the people behind your water.


The Santa Clara Valley Water District relies heavily on high-tech equipment to analyze the quality of the water we send through our system to retailers who then get it to residents and businesses. This advanced technology helps us ensure the delivery of safe, clean water each day.

But to really know what that flavor is that’s coming through in the water, we rely on the most advanced machine of all, one that takes nine months to manufacture and a lifetime to calibrate: the human nose.

A machine can tell you a lot, such as the levels of taste and odor compounds in the water, but they have their limits. The palates of the members of our Flavor Profile Analysis panel – or “water sommeliers,” if you will – can tell you what those taste and odor compounds amount to: a smell or taste that’s musty, grassy, fishy, sweet, bitter, medicinal … you name it, and they’re on the lookout for it. And like sommeliers tasting fine wine, they can even tell you the mouthfeel: Astringent? Soapy? Drying?

Why do we need water sommeliers?

The water district isn’t the only water agency in the state that makes use of the human palate to discern any taste or odor anomalies in the water. Metropolitan Water District in Los Angeles started the practice, and it has spread to various water districts throughout the state, including our own.

Their work is valuable, especially during the high season from May to October, when we experience more algae blooms in our water supply. Hot summer sun warms up the water in reservoirs and in the Sacramento-San Joaquin Delta, increasing the chance of algae blooms which can leave behind flavor compounds that create a variety of smells and tastes in the water.

Recently, we have had this issue with geosmin, an algae compound that gives water an earthy or musty flavor. Our panel members have been key in monitoring the intensity of the compound, helping the water district to mix water from different sources to mitigate the smell and taste.

How does the Flavor Profile Analysis Panel work?

 Meeting every Tuesday afternoon during the high season and every other Tuesday during the off season, the panel, composed entirely of water district employees with refined palates, convenes to smell and taste one water sample from each of our three water treatment plants, plus one sample of raw, or untreated, water that they’ll smell but not taste.

They get together in a special room in our water quality lab with an isolated ventilation system, so as not to draw in smells from other places and interfere with the tasting. They can’t wear perfume or hand lotion or other scented potions, and to make sure their palates are clear for their 3 p.m. tasting, they are advised not to eat or drink after 1 p.m.

When they’re ready to smell and taste, they each have a set of glasses with glass lids labeled 1-4, plus one glass of distilled water to have something completely flavorless and odorless to compare their water samples to. The samples are warmed to release any odor or taste compounds and mimic what the customer might be receiving.

They start by sniffing the distilled water. Then they’ll take the lid off glass No. 1 and sniff, marking their rankings on a grid for Sample No. 1’s aroma. The rating system starts at T for trace, which is just barely noticeable, and increases by increments of one-half, all the way up to 3, which is unpalatable.

Next, after judging Sample No. 1’s aroma, they’ll sniff the distilled water again, to refresh their memories and give their palate a comparison, and then move on to Sample No.2.

Once they have sniffed and rated each sample, with a cleansing sniff of distilled water in between, they start to taste. The pattern is the same:

  1. sip distilled water
  2. sip Sample No.1
  3. rate the flavor
  4. repeat with each other sample

Once they’re done, the ratings are compiled and the information is sent out to the Water Quality Unit and others to make sure they’re aware of and can take steps to mitigate any bad tastes and odors, if necessary.

They get a tune-up, too. Once a year, the Water Quality Lab will mix up some samples with a variety of intensities of salty, sour, bitter and sweet tastes to calibrate the panel members’ palates.

Some panel members are more sensitive to certain flavors than others. The combination of their palates helps them pick up on even very faint flavors and aromas. That’s why there must be at least four permanent members of the panel each time they meet to taste. If not, their tastings essentially don’t count for that week.

How are the sommeliers chosen?

 Spots on the Flavor Profile Analysis Panel aren’t easy to come by. Employees who are interested have to prove themselves with a test familiar to so many grade schoolers – the scratch-and-sniff.

Interested employees get four booklets with 10 scratch-and-sniff tests in each. For each test, they have to scratch, sniff and identify the scent. Then they send their answers in for scoring. They can get up to three scent identifications wrong; any more than that, and they’re out of the running.

If they pass, they begin their training, which lasts for six months, during which they must attend and participate in every meeting of the panel. During this training time, their ratings don’t count.

If they make it through training, they become full-fledged members of the tasting panel, and along with all the high-tech equipment, their palates become an integral part of the water district’s water quality control system.

Johanna Castro is a senior engineer and has been a water sommelier for 17 years – her entire time at the water district. She said years ago, they tried using a machine to determine which water had flavors and odors, but it never really worked.

“Ultimately,” she said, “it’s the human nose that’s most sensitive.”


  1. Fascinating ! Thank You. This level of scrutiny gives me more confidence in the local water supply. I don’t buy bottled water because I trust my tap water to be better regulated and checked. Besides, who wants to drink water from a chemical leaching plastic bottle? Question: Since the quality of water can vary by season, should I consider changing the water in my emergency supply stock during the rainy season or does it matter?


    1. Hi Marc,
      Thanks for your question. The Department of Homeland Security has a really helpful website on preparing emergency kits. This page from their site has good advice about storing water either that you buy bottled beforehand or that you bottle yourself. We hope this helps!


  2. How about SAFE drinking water? Is there a group that cares about our health? HFSA is highly toxic and you are adding it to our water in December? Its bad for my body, my animals and plants. There is enough science out there that shows proof that it negatively affects our brains, bones, kidneys and well-being, even at a small amount. Will you be testing every single batch of HFSA to see if its contaminated with many other toxins since you are using the cheapest quality of Fluoride?


    1. Marlies,
      Thank you for your concern about water quality. The Santa Clara Valley Water District takes water quality very seriously, and works extremely hard to provide safe, clean, reliable water to 1.9 million people in Santa Clara County. We frequently test the quality of the water we provide at our state-of-the-art laboratory, and our water consistently meets or exceeds all drinking water standards set by the state and federal governments. Learn more on our water quality web page: http://www.valleywater.org/Services/ProtectingYourWater.aspx.

      Regarding fluoridation, the selected fluorosilicic acid is certified for compliance with the American National Standards Institute (ANSI) and National Sanitation Foundation (NSF) Standard 60. ANSI/NSF Standard 60 ensures that chemicals used to treat drinking water do not contribute contaminants to the water that could cause adverse health effects.


      1. Please remind me WHY Fluorosilicic Acid is being added to the water supply? If this is just to prevent dental cavities, I would just as soon not have it. Our water supply was just fine before this was added and I can get fluoride from toothpaste. The fewer unnecessary chemicals you add to my drinking and bathing water, the better…


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: