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How to make kombucha safely at home

How to make kombucha safely: glass or food-grade plastic, pH 4.2 or lower on a meter, never below 2.5, mold rules, bottle pressure and who should skip it.

Updated November 2026 · 7 min read

A kombucha SCOBY floating on sweet tea in a brown crock
Photo: Florence Bouche, CC BY 2.0, via Flickr
The short version
  • How to make kombucha safely: sweet tea, a SCOBY and starter liquid in a glass or food-grade plastic jar, covered with cloth, at room temperature.
  • Virginia Tech Extension: monitor with a calibrated pH meter until the brew reaches pH 4.2 or lower, and do not let it fall below 2.5.
  • Never brew or store kombucha in ceramic, glazed earthenware or lead crystal: CDC and UGA warn the acid can leach toxic metals.
  • Fuzzy, dry mold on the SCOBY or surface means discard everything, per UGA.
  • Kombucha contains some alcohol and keeps fermenting in the bottle. UGA advises people who are pregnant, lactating, immunocompromised or prone to acidosis not to drink it; we don’t recommend homemade kombucha for children.

How to make kombucha safely is a better question than how to make it fast, because kombucha is an acidic fermented tea made with a mixed culture of yeast and bacteria, and the acidity is what keeps harmful microbes out. Get the acidity, the container and the cleanliness right and the rest is taste.

This guide is built on three public sources: Virginia Tech Extension FST-297 (kombucha brewing under the FDA Food Code), University of Georgia Extension C1312 (“What’s the word on homemade kombucha?”) and the CDC’s 1995 MMWR report on illness possibly associated with kombucha. We make no health claims for kombucha; we summarize safety guidance and maker listings and did not brew these kits.

Who should not drink homemade kombucha

UGA Extension says consumption is “not advised as potential health risks are unknown” for people with a susceptibility to acidosis or a weakened immune system, and for people who are pregnant or lactating. People who have been told to avoid alcohol should know that kombucha contains some, and UGA suggests checking alcohol content first.

The CDC’s 1995 report described two cases of severe lactic acidosis, one fatal, in people who drank homemade kombucha daily; the cause was not established. The CDC noted that about 4 oz a day “may not cause adverse effects in healthy persons” and that risks for people with health problems are unknown.

Site policy on children

We don’t recommend homemade kombucha for children. It contains some alcohol, it is acidic, and the risks are not well studied; ask a pediatrician. This is our policy, not a statement from UGA or the CDC.

Kombucha safetyFerment in food-grade glass or plastic, never ceramic, glazed earthenware or lead crystal. Check with a calibrated pH meter that it reaches 4.2 or lower (and not below 2.5); discard moldy SCOBYs. Extension services advise people who are pregnant, immunocompromised or prone to acidosis not to drink it; we don’t recommend homemade kombucha for children.Source: Virginia Tech FST-297; UGA Extension C1312; CDC MMWR 1995

Containers and equipment

What to brew and store kombucha in

MaterialOK?Why
Glass jar (plain, not lead crystal)✓Non-reactive; easy to see the SCOBY and mold
Food-grade plastic✓Virginia Tech: non-metallic, food-grade containers
Ceramic, glazed earthenware, crockery✗CDC and UGA: acid can leach lead or other toxic elements from glazes
Lead crystal✗CDC: do not brew or store kombucha in it
Metal vessels✗Virginia Tech specifies non-metallic fermentation containers
Cloth or coffee-filter cover with a band✓Lets air in and keeps insects out (Virginia Tech)

Source: CDC MMWR 1995; UGA C1312; Virginia Tech FST-297

Two large glass jars of brewing kombucha on a kitchen counter
Glass jars are the safest container for kombucha.Photo: dvanzuijlekom, CC BY-SA 2.0, via Flickr

Some kombucha dispensers are sold in stoneware. Given the CDC and UGA advice on ceramic and glazed earthenware, stick to plain glass or food-grade plastic for brewing and storage.

Measure the pH properly

Virginia Tech says to use a calibrated pH meter and follow the maker’s calibration instructions. pH strips in kits give a rough reading, but the 4.2 line is where precision matters, so a food pH meter with calibration buffers is the better tool.

The pH window: 4.2 down to 2.5

Kombucha pH targets

Virginia Tech Extension FST-297

2.5 floor4.2 ceiling27
Too acidic, below 2.5: 2–2.5Target zone: 2.5–4.2Not yet safe, above 4.2: 4.2–7
Source: Virginia Tech Extension FST-297
A pocket pH meter probe dipped into water in a white tub
Check pH with a meter rather than by taste.Photo: Ildar Sagdejev ( Specious ), CC BY-SA 4.0, via Wikimedia Commons

Virginia Tech’s guidance is to monitor pH during fermentation until the product reaches 4.2 or below, and not to let it fall below 2.5 because that becomes dangerously acidic. UGA also warns against letting kombucha become too acidic. Mold is more likely when the brew is not acidic enough, which is why starter liquid from a previous batch goes in at the start: it lowers the pH right away.

4.2Reach this pH or lower during fermentationVirginia Tech FST-297
2.5Do not go below this pHVirginia Tech FST-297
0.5%Above this ABV, kombucha is regulated as alcoholVirginia Tech FST-297
4 ozDaily amount CDC said may not harm healthy peopleCDC MMWR 1995

How to make kombucha safely, step by step

  1. Clean and sanitize

    UGA: wash equipment with warm water and dish soap; to sanitize, submerge it in water of at least 171°F for at least 30 seconds, or use a no-rinse sanitizer at label dilution. Let glass cool before adding liquids so it does not crack.

  2. Brew sweet tea

    Steep tea in hot water, dissolve the sugar your kit or recipe calls for, remove the tea and let it cool to room temperature. Hot tea kills the culture.

  3. Add starter liquid and the SCOBY

    Pour the cooled tea into the jar, add the starter liquid that came with the SCOBY (it lowers the pH at once), then the SCOBY. Do not share or accept SCOBYs of unknown history; Virginia Tech advises against sharing them.

    Fermentaholics Organic Kombucha SCOBY + 12 oz Starter Tea
  4. Cover and ferment

    Cover with a tight-weave cloth or coffee filter secured with a band, away from direct sun. Many kits suggest the mid 70s °F; a heat mat helps in a cold room (Fermentaholics lists a 75–85°F target).

    Fermentaholics Kombucha Heat Mat
  5. Check pH and look for mold

    Measure pH with a calibrated meter. Keep going until it reads 4.2 or lower. Fuzzy, dry patches of white or colored mold mean discard the tea and the SCOBY, then clean and sanitize the jar (UGA).

  6. Taste and decide

    Once the pH is in range, taste. Longer fermentation makes it more sour and lowers the pH further; stop before it nears 2.5.

  7. Bottle and refrigerate

    Reserve starter liquid for the next batch, bottle the rest and refrigerate. Fermentation continues in the bottle, building pressure and alcohol, so cold storage matters.

    Ilyapa 16 oz Amber Swing-Top Bottles, 12-PackFermentaholics 16 oz Brown Swing-Top Bottles, 6-Pack
  8. Log each batch

    Note dates, temperature and pH readings in the brew-day log.

Alcohol and carbonation in kombucha

Kombucha yeast make alcohol, and bacteria turn some of it into acids. How much remains depends on time, temperature and the culture. Virginia Tech notes that commercial kombucha above 0.5% ABV is regulated as an alcoholic beverage by TTB and that alcohol can rise in unpasteurized product during storage. Homemade kombucha is not tested, so treat it as possibly containing alcohol: people avoiding alcohol, anyone driving, and people under 21 should skip it.

Kombucha with raspberries in a jar for a second fermentation
A fruit second fermentation adds fizz and a little alcohol.Photo: Lukas Chin, CC BY-SA 4.0, via Wikimedia Commons

A second fermentation in sealed bottles with fruit or juice adds sugar and makes it fizzy. It also builds pressure. Use bottles made for carbonation (swing-tops or crown-cap bottles), fill them in a closed box, “burp” or chill them after a day or two, and refrigerate. Read how to bottle homebrew for the bottle-bomb basics.

Avoid bottle bombsBottle only after the gravity reads the same 2–3 days in a row, measure priming sugar with a calculator, use standard bottles only to about 3 volumes, store them in a closed box at room temperature and refrigerate once carbonated.Source: BYO carbonation priming chart
Know what’s in the glassHomebrew is often stronger than commercial beer. One US standard drink is 14 g of alcohol: 12 oz of 5% beer or 5 oz of 12% wine. Brewing and drinking are for adults 21 and over; never drink and drive.Source: NIAAA: What is a standard drink?

Cleaning, sanitizing and SCOBY care

Kombucha brewers borrow a lot from beer and wine sanitation. Clean first with warm water and an unscented dish soap or brewery cleaner, rinse well, then sanitize. UGA’s method is hot water of at least 171°F for at least 30 seconds; a no-rinse sanitizer used at label dilution is the other common route. Residue from scented soaps can affect the culture, so rinse thoroughly. The difference between the two steps is covered in cleaning vs sanitizing.

A pale kombucha SCOBY lifted out in a mesh strainer
A healthy SCOBY is pale and firm.Photo: ~Twon~, CC BY 2.0, via Flickr

Between batches, keep the SCOBY in a covered glass jar with enough finished kombucha to cover it; the acidic liquid protects it. A SCOBY hotel at room temperature, away from fruit flies, is the usual approach.

When to replace it: if a SCOBY grows mold, smells rotten or unlike vinegar, or the batches stop reaching pH 4.2, discard it and start with a fresh culture from a known source. Virginia Tech advises against sharing SCOBYs, which also rules out taking one of unknown history from a friend.

Chemicals: label directions onlyUse sanitizers, cleaners, acids and salts only at the dilution and contact time on the label. Wear eye protection with acids and powders, add acid to water, keep them away from children and food prep. Star San is EPA-registered (Reg. No. 65001-1) as a no-rinse sanitizer at label dilution.Source: EPA Star San label

Common kombucha mistakes

  • Skipping the starter liquid. Without it the tea starts at a high pH, where mold has an opening.
  • Trusting strips at the 4.2 line. Use a calibrated meter as Virginia Tech advises.
  • Ceramic or crystal vessels. CDC and UGA advise against them.
  • Scraping off mold and carrying on. UGA: discard the tea and the SCOBY.
  • Leaving bottles warm for days. Pressure and alcohol keep rising.
  • Believing the marketing. This site makes no health claims for kombucha; treat it as a homemade drink with real safety rules, not a remedy.

Which kit should you start with?

A 1 gal kit with a glass jar, cloth cover and SCOBY with starter liquid is the simplest start; add a calibrated pH meter if the kit only includes strips. Kits that include swing-top bottles save a step for second fermentation. Browse the wine, cider, mead and kombucha category or the beyond beer hub; meters are in hydrometers and meters. The AHA’s Home Fermentation Day in August is a natural time to start one; see the seasonal calendar.

Gear picks for this guide: best kombucha starter kits and best pH meters for brewing.

ABV calculatorWork out ABV from OG and FG with the standard and high-gravity formulas, hydrometer temperature correction,…Printable brew-day log and recipe sheetFree brew-day log: record recipe, water and salts, mash, gravities, yeast, fermentation temperatures,…

Questions

Is homemade kombucha safe?
For healthy adults, extension services treat it as safe when brewed in glass or food-grade plastic, kept clean, and fermented to pH 4.2 or lower (not below 2.5), with moldy batches discarded. UGA advises some groups not to drink it.
Does kombucha have alcohol?
Yes, some. Virginia Tech notes kombucha over 0.5% ABV is regulated as alcohol, and alcohol can rise in the bottle. Homemade kombucha is untested, so assume it contains alcohol.
What pH should kombucha be?
Virginia Tech says 4.2 or lower, checked with a calibrated pH meter, and not below 2.5.
Can I brew kombucha in a ceramic crock?
No. The CDC and UGA warn that kombucha’s acidity can leach lead and other toxic elements from ceramic and glazed earthenware. Use plain glass or food-grade plastic.
What does mold on a SCOBY look like?
UGA describes dry, fuzzy patches, white or colored, on the SCOBY or the surface. If you see it, discard the tea and the SCOBY and sanitize the jar.
Who should not drink kombucha?
UGA advises against it for people prone to acidosis, people with weakened immune systems, and people who are pregnant or lactating. We also don’t recommend homemade kombucha for children.
Do I need a pH meter for kombucha?
Virginia Tech recommends a calibrated pH meter because the 4.2 target needs a reliable reading. Strips give a rough idea; a food pH meter with calibration buffers is more dependable.

Sources

  1. Virginia Tech Extension FST-297: Kombucha brewing under the FDA Food Code
  2. UGA Extension C1312: What’s the word on homemade kombucha?
  3. CDC MMWR (1995): Unexplained severe illness possibly associated with consumption of kombucha tea
  4. NIAAA: What is a standard drink?
  5. CDC: Moderate alcohol use