Brew control
This site has told you a dozen times to use filtered water without once saying what that means. Two different chemicals are involved, and only one of them goes away on its own.
By Scooter M.·Published September 9, 2026
The short answer
Sometimes. Municipal water is disinfected with either free chlorine or chloramine, and they behave completely differently: free chlorine dissipates from water left standing and is driven off by boiling, while chloramine is far more stable and does neither. Find out which one your utility uses — its annual water quality report says so, free — then treat accordingly.
Chlorine and chloramine are added to municipal supplies for one purpose: to suppress microbial life all the way from the treatment plant to your tap. Kombucha is microbial life. That is the entire problem in one sentence, and it is why every page on this site that touches a culture eventually says “filtered water” and moves on.
The effect is rarely dramatic. A batch made with treated water does not die visibly; it goes slow. The culture takes longer to acidify, the batch spends longer in the window above pH 4.2 where it is not yet defending itself, and the brewer concludes the culture was weak. It usually was not. Water kefir grains show it fastest, because their whole cycle is 24 to 48 hours and there is nowhere for a delay to hide, which is why the published guidance for those is unchlorinated water rather than a suggestion.
None of which means tap water is automatically a problem. Plenty of people brew good kombucha straight from the tap for years. Whether you can depends on which chemical your utility uses and how much of it is left by the time it reaches you — and both of those are knowable rather than guessable.
This is the distinction the internet consistently collapses, and it is the one that decides which fix you need.
| Free chlorine | Chloramine | |
|---|---|---|
| What it is | Dissolved chlorine gas / hypochlorite | Chlorine bonded to ammonia |
| Standing uncovered overnight | Dissipates | Does not meaningfully dissipate |
| Boiling | Driven off | Far more stable; not a reliable removal |
| Ordinary carbon filter at tap flow | Removed | Not reliably — needs long contact time |
| Campden tablet | Removed | Removed |
| Why utilities use it | Cheap, effective, dissipates fast | Persists further into the network |
Read the second and third rows together and the folk advice makes sense at last. “Leave it out overnight” and “you boil the water for the tea anyway” are both perfectly good answers — if your utility uses free chlorine. On a chloramine system they are simply wrong, and the person repeating them is not lying, they are on a different water supply.
Before buying anything, find out which one you have. Every community water system in the United States publishes an annual water quality report — the Consumer Confidence Report — and it states the disinfectant in use. It is free, it is specific to your supply, and it is more authoritative than any test you can run at home.
If you cannot find it, or you are on a supply that has changed treatment recently, the home version is a free-and-total chlorine strip. Free chlorine is the unreacted kind; total chlorine is everything. The gap between the two readings is combined chlorine, which on a municipal supply is essentially your chloramine. That is a genuinely useful measurement and almost nobody knows a single strip gives it to you.
The same logic runs through this whole site. A number you took yourself beats an argument you read, which is exactly why a vial of pH strips is the cheapest useful thing in the cupboard.
One strip that tells you which chemical you are dealing with, the cheap treatment that handles both, and the plumbed option for anyone filtering water by the gallon.
Hach
The only product here that answers the question before you spend anything else — it reads free and total chlorine on the same strip, and the gap between those two numbers is your chloramine.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
Campden
The only cheap thing on this page that deals with chloramine as well as chlorine, at a published dose of one 500 mg tablet per 20 gallons, acting essentially on contact.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
MoreBeer
A complete carbon-block setup rather than a bare cartridge — and the only product here whose seller publishes the flow rate chloramine removal actually requires.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
The published dose is one 500 mg tablet per 20 gallons. A kombucha batch is one gallon. That arithmetic is awkward and it is the honest weak point of an otherwise ideal product: you are crushing a tablet and using a fraction of the powder, which is not a precise operation in a home kitchen.
In practice brewers crush a tablet, dissolve it into a measured volume of water, and dose from that — or simply accept that a generous crumb in a gallon is still a very small quantity of sulfite that is largely consumed reacting with the chlorine it was added to remove. Neither approach is published as a kombucha method by anybody, and this page is not going to invent one. What is published is the brewing-water dose above, and the fact that it acts on contact rather than needing a wait.
Two things worth saying plainly. Sulfites are a genuine sensitivity for some people, and anyone avoiding them should filter or buy water instead. And a tablet does nothing about minerals, sediment or taste — it addresses one thing precisely, which is also why it is cheap.
A carbon block setup is the most expensive answer on this page to a problem a crushed tablet solves, and for a gallon a week it is hard to justify. It earns its place at volume: a continuous brew being topped up weekly, several ferments running at once, or a household brewing beer alongside kombucha.
The specification that matters is the one almost nobody publishes. MoreBeer states that chloramines can be removed by carbon filtration given long contact time, and recommends a fill rate under 1 gallon per minute to achieve it. That single sentence is the difference between a filter that solves your problem and one that quietly does not — and it means a filter run at normal tap pressure is a chlorine filter regardless of what the box says.
The rest of the arithmetic is straightforward: a cartridge published at 750 gallons, replaced at roughly 800 gallons or one year, whichever comes first. At a gallon of kombucha a week that is a cartridge a year on the clock rather than on the volume, which is the honest running cost.
Water is a fashionable thing to blame and usually not the culprit. Before you re-plumb the kitchen, rule out the two variables that cause far more stalled batches.
| Symptom | Most likely cause | Check |
|---|---|---|
| Still sweet at day 10, no sourness | Temperature | Strip thermometer on the glass, not the room |
| pH still above 4.2 at day 3 | Too little starter tea, or cold | Measure the starter at ten percent of batch volume |
| Slow, batch after batch, everything else right | Water | Free and total chlorine strip, or the utility report |
| Was fine, suddenly slow, nothing changed | Water — the utility may have switched treatment | Utility report; many switch seasonally |
That last row is the genuinely interesting one. Some utilities alternate between free chlorine and chloramine at different times of year, which produces exactly the story brewers find baffling: a setup that worked for a year suddenly running slow with no change at your end. Batches that go too far and batches that stall are both timing problems, and water is one of the inputs that quietly moves the timing.
Two places the same rule applies and people forget.
The first is rinsing. Never rinse a pellicle or a culture under the tap — you are running the exact chemical you have been avoiding straight over the organisms. The cleaning routine covers using a little of the batch's own kombucha instead.
The second is the sweet tea itself. If you are treating water, treat the water you brew the tea with, not just the water you top up with — the tea is most of the batch volume. Tea and sugar for kombucha covers the rest of the feedstock, and water is the ingredient on that page that gets one line and deserves this one.
Heads up: some links on this page are affiliate links. If you buy through one we may earn a commission at no extra cost to you. It never changes a ranking, and we take no payment for placement. The full version.
Ranked on the published rubric. Every row jumps to that product's full write-up below; the button goes straight to Amazon.
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 | Score8.2 Hach Free & Total Chlorine Test Strips, 0-10 mg/L (2745050) The only product here that answers the question before you spend anything else — it reads free and total chlorine on the same strip, and the gap between those two numbers is your chloramine. | Finding out what is actually in your tap | 8.2out of 10 | |
| 2 | Score8.3 Campden Campden Tablets, Potassium Metabisulfite (25 count) The only cheap thing on this page that deals with chloramine as well as chlorine, at a published dose of one 500 mg tablet per 20 gallons, acting essentially on contact. | Removing chloramine in one stir | 8.3out of 10 | |
| 3 | Score7.5 MoreBeer Water Filter Kit, 10 in. A complete carbon-block setup rather than a bare cartridge — and the only product here whose seller publishes the flow rate chloramine removal actually requires. | Filtered water at the tap, every time | 7.5out of 10 | |
| 4 |  Micro Essential Lab Hydrion 9200 Spectral pH Strips, 0.0-6.0 A 0.0 to 6.0 range in 0.5 steps, which puts four separate color matches inside the 2.5 to 3.5 window kombucha lives in — a 1-to-14 strip gives you one. | Reading kombucha’s actual pH band | 8.8out of 10 |
#1 · Finding out what is actually in your tap
The only product here that answers the question before you spend anything else — it reads free and total chlorine on the same strip, and the gap between those two numbers is your chloramine.
Who it is for. Anyone whose culture keeps stalling for no visible reason, and anyone who wants to know whether the cheap fix or the expensive one is the right one.
Source: Hach published product specification for Free & Total Chlorine Test Strips, 0-10 mg/L, catalog 2745050 (range, graduation steps, parameters measured, pack sizes, dip-and-read method), hach.com and ca.hach.com product detail pages, retrieved 2026-09-09
Skip it if. Your utility’s annual water quality report already states which disinfectant it uses. That document is free, and it answers the same question without a purchase.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
#2 · Removing chloramine in one stir
The only cheap thing on this page that deals with chloramine as well as chlorine, at a published dose of one 500 mg tablet per 20 gallons, acting essentially on contact.
Who it is for. Anyone on a chloramine system who wants the problem solved for the price of a coffee, without a filter housing under the sink.
Source: Campden tablet specification and dosing as published by homebrew retailers: The Electric Brewery (500 mg potassium metabisulfite treats up to 20 gallons at up to 3 ppm chlorine or chloramine, works instantaneously, 12 month shelf life) and Homebrewers Mercantile (25 tablet count, active ingredient, crush-and-dissolve instructions), retrieved 2026-09-09
Skip it if. Your utility uses free chlorine rather than chloramine. Standing the water overnight or boiling it costs nothing and does the same job.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
#3 · Filtered water at the tap, every time
A complete carbon-block setup rather than a bare cartridge — and the only product here whose seller publishes the flow rate chloramine removal actually requires.
Who it is for. Someone running a continuous brew, several ferments at once, or brewing beer alongside kombucha — where filtered water by the gallon is a standing requirement rather than an occasional one.
Source: MoreBeer published specifications for the Water Filter Kit - 10 in. (kit contents, what it removes, 800 gallon or 1 year replacement interval, cold water only) and for the matching Carbon Block Water Filter - 10 in. (10 micron rating, 750 gallon capacity, and the published chloramine contact-time and sub-1-gallon-per-minute fill rate statement), morebeer.com, retrieved 2026-09-09
Skip it if. You brew a gallon a week. The volume does not justify the hardware, and a tablet or a jug of spring water covers it for a fraction of the cost.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
#4 · Reading kombucha’s actual pH band
A 0.0 to 6.0 range in 0.5 steps, which puts four separate color matches inside the 2.5 to 3.5 window kombucha lives in — a 1-to-14 strip gives you one.
Who it is for. Every kombucha brewer. This is the cheapest instrument on the site and the one that answers the safety question.
Source: Micro Essential Lab published product specification (range, 0.5 graduations, 100 strips per vial, packaging), microessentiallab.com/product/hydrion-9200-spectral-0-0-6-0-plastic-ph-strip, fetched 2026-09-01. Strip length from retailer listings.
Skip it if. You need a number to one decimal place for a written record. Buy a calibrated pH meter; strips are for reading a band, not a value.
#ad No live price feed yet, so no number is shown rather than a stale one. How this is funded.
Every specification cited on this page came from one of these documents, retrieved on the date shown against the product it belongs to.
Temperature and pH — the two readings that decide a batch, and the strips, mats, thermometers and controllers that give them to you.
Which teas work and which damage a culture over time, why herbal infusions are not tea, and the ratios for a one-gallon batch.
Rehydration windows, working ratios, temperature bands and shelf life for dehydrated grains — and what to do when they stop multiplying.
The pH numbers that matter, why a narrow-range strip beats a 1-to-14 one, and how to test a batch without contaminating it.
Why kombucha does not need a beer-brewing sanitizing regime, what genuinely needs cleaning, and the products that damage a culture.