Brewing Water Treatment: The UK Home Brewer’s Guide for 2026

Beer is roughly 90% water, yet water is the ingredient most UK home brewers ignore for longest. This guide is a desk-research round-up of the products and techniques UK brewers reach for in 2026, drawn from supplier listings, brewing references and the well-trodden advice on forums like The Homebrew Forum. It is written to help you decide what to buy and why, not to replace a proper water report for your own postcode.

Quick Picks

If you buy nothing else, buy the Campden tablets. Everything below explains where the salts and acids fit once you are ready to fine-tune.

Why brewing water matters

Water is not a neutral background. It carries dissolved gases and minerals that interact with your grain, hops and yeast at every stage. There are three separate reasons water treatment is worth your attention, and it helps to keep them distinct because they call for different products.

1. Chlorine and chloramine cause off-flavours

Most UK mains water is disinfected with chlorine or, increasingly, chloramine (a more stable chlorine-ammonia compound). Both are harmless to drink but hostile to beer. During fermentation, yeast produce natural phenolic compounds, and brewing references consistently note that chlorine and chloramine react with these phenols to form chlorophenols. The result is an unmistakable plaster, plastic, TCP or “medicinal” character, often described as a sticking-plaster or antiseptic note. It is one of the most common faults in beer made with untreated tap water.

The important practical point, echoed across brewing guides, is that chloramine is deliberately more stable than free chlorine. Letting water stand overnight or giving it a rolling boil will drive off some free chlorine, but is far less effective against chloramine, and boiling large volumes is slow and energy-hungry. This is exactly why a chemical dechlorinator is the standard answer (more on Campden tablets below).

2. Mineral and ion balance shapes the beer’s character

Once the water is clean, the dissolved minerals become a flavour tool. The two ions brewers manipulate most are sulphate and chloride, and the ratio between them nudges a beer towards “crisp and bitter” or “soft and malty”.

Brewing references broadly describe a roughly 1:1 sulphate-to-chloride ratio as balanced. Tilting towards sulphate (for example 2:1 or 3:1 sulphate to chloride) is associated with accentuated, drier hop bitterness — the logic behind the famously sulphate-rich water of Burton-on-Trent, where “Burtonising” can push sulphate to very high levels. Tilting the other way, towards chloride (2:1 or 3:1 chloride to sulphate), is associated with a fuller, rounder, more malt-forward impression favoured in stouts, milds and sweeter bitters. Calcium sits alongside both: it supports yeast health, mash chemistry, protein precipitation (helping clarity) and head retention.

A couple of ballpark figures widely cited in brewing water guides help set expectations. Sulphate is commonly targeted somewhere in the region of 20–150 ppm depending on how hop-forward you want the beer, and magnesium (from Epsom salts) is usually kept modest, with references suggesting you avoid exceeding roughly 50 ppm. These are attributable rules of thumb rather than hard limits, and your own targets should come from a calculator (see below) rather than guesswork.

3. Mash pH affects conversion and clarity

If you brew all-grain, water treatment also underpins mash pH. Brewing references generally place the useful mash pH window at around 5.2–5.6 measured at room temperature (which tends to read a touch lower, roughly 5.1–5.4, at mash temperature). The starch-converting enzymes, alpha- and beta-amylase, work best in that band. Drift much above it — towards 5.8 and beyond — and guides note that conversion efficiency falls, husk tannins are extracted more readily, and the beer can taste harsh or astringent. Very dark, roast-heavy grists tend to push pH down, while pale, low-mineral grists can sit too high, which is where acids and calcium additions come in.

Two things are worth stressing honestly here. First, pH matters most to all-grain brewers; if you brew from malt extract or kits, the maltster has already handled the mash, so pH is far less of a concern. Second, meaningful pH work really needs measurement — a calibrated pH meter or, at a pinch, narrow-range pH strips — rather than dosing blind.

Comparison of key water-treatment products

The table below summarises the common UK additions. Prices are approximate, move around between retailers, and should be treated as a rough guide only rather than a quote.

The key additions, one by one

Campden tablets: the beginner’s essential

If you take one thing from this guide, take this: dechlorinate. Campden tablets are small, pressed tablets of sodium metabisulphite (or the potassium version), and brewing suppliers describe them as removing both chlorine and chloramine almost instantly — a decisive advantage over standing or boiling, which struggle with chloramine.

Dosage is generous and hard to get wrong. The widely quoted rate is one tablet per 20 gallons (around 90 litres) of water; for a typical 23-litre home batch, that works out at roughly half a crushed tablet. Balliihoo’s product listing for its VinClasse tablets echoes the standard “one tablet treats 20 gallons” guidance and notes the pressed tablets give an easily measured dose without risking sulphite overtones. The usual method is to crush the tablet, stir it into your fresh water before adding anything else, and give it a few minutes to work.

On price and value, this is the bargain of the shelf. Balliihoo lists a tub of 100 VinClasse Campden tablets at around £4.49 at the time of writing; at half a tablet per batch, that is comfortably under 5p of treatment per brew. A safe-usage note: metabisulphite dust is an irritant, so crush tablets without inhaling the powder, and people with a sulphite sensitivity should be aware of what they are handling. Only add Campden to fresh water, not alongside other brewing ingredients.

Gypsum: for hoppy, pale and dry beers

Gypsum, or calcium sulphate, raises both calcium and sulphate. Suppliers and brewing references position it as the classic addition for pale, bitter and hop-forward beers, because the added sulphate accentuates a dry, crisp bitterness — the ion signature behind Burton-brewed pale ales. It also lifts calcium, which supports fermentation, helps proteins drop out for clarity, and aids head retention. Retail 100g pouches are typically only a few pounds and last a long time, since additions are measured in grams per batch. Because it dissolves best in warm water and can clump once opened, store it dry and sealed. The safe-usage watchword is restraint: sulphate is easy to overdo, and too much can tip hop bitterness from crisp into harsh, which is why a calculator is worth using rather than eyeballing spoonfuls.

Calcium chloride: for malty, full-bodied beers

Calcium chloride is gypsum’s counterpart, raising calcium and chloride rather than sulphate. Suppliers describe it as promoting a softer, fuller, rounder palate, which makes it the natural choice for stouts, milds, porters and malt-led bitters. It is usually sold as flakes (sometimes as a ready-made solution), and brewing references note it is hygroscopic — it readily absorbs water and clumps — so keep the tub tightly closed. As a rough figure widely cited in brewing water references, around one gram of calcium chloride per gallon shifts the water by something like 72 ppm calcium and 127 ppm chloride, which shows how little you need. Expect to pay a few pounds for 100g, or a little more for a 500g tub if you brew often.

Epsom salts: a small, careful lever

Epsom salts (magnesium sulphate) add magnesium along with sulphate, and are generally used in much smaller amounts than gypsum. A little magnesium can support yeast and add a touch of firmness, but brewing guides caution against pushing magnesium too high — around 50 ppm is a commonly cited ceiling — because excess magnesium can taste sour or laxative. Treat Epsom salts as a fine-tuning ingredient rather than a workhorse. They are inexpensive, usually only a couple of pounds a pack, and a single pack will outlast many brews.

Lactic acid and CRS/AMS: adjusting pH and alkalinity

Where salts change the mineral profile, acids change the pH and alkalinity. Lactic acid — the same acid found in yoghurt and sourdough — is popular precisely because, as brewing references note, it lowers pH without altering your sulphate or chloride balance. That makes it a clean tool for pale, low-mineral grists that would otherwise mash too high, and for acidifying sparge water. The Malt Miller lists 80% lactic acid in 250ml and 500ml bottles for a modest single-figure sum; a little goes a long way, so the smaller bottle suits most home brewers. Always adjust against a measured pH reading rather than by volume alone, and handle concentrated acid with care — add it to water, not the other way round, and keep it away from skin and eyes.

CRS, also sold as AMS (carbonate reducing solution), is a different animal: brewing references describe it as a blend of hydrochloric and sulphuric acids designed to cut carbonate/alkalinity in hard water. Because it is acid-based, it also nudges chloride and sulphate upwards, so on some water supplies it can do double duty — reducing alkalinity while shifting the ion balance. It suits brewers on hard, alkaline water who want to knock back carbonate before mashing. As with lactic acid, it is a strong acid blend, so follow the supplier’s dosing and safety guidance closely.

Let a calculator do the arithmetic

You do not need to compute ppm by hand. Free and low-cost water calculators — Martin Brungard’s Bru’n Water spreadsheet, the Brewfather water calculator, Brewer’s Friend and EZ Water among them — let you enter your source water figures and a target profile for the style, then estimate the gypsum, calcium chloride, Epsom and acid additions needed, along with a predicted mash pH. The one input they cannot invent is your starting water. Get that from your water supplier’s published report or a dedicated brewing water test rather than guessing, because the same salt addition behaves very differently on soft Manchester-type water than on hard, chalky southern supplies.

If you do just one thing

Dechlorinate with a Campden tablet. Half a crushed tablet stirred into your brewing water, a few minutes before you add anything else, is the cheapest and most reliable upgrade you can make to a home brew. It removes the single most common and most obvious water fault — the plastic/TCP off-flavour from chlorine and chloramine — for a few pence a batch. Salts, acids and calculators are worthwhile once you are chasing a particular style, but they are refinements. Clean water comes first.

FAQ

Do I actually need to treat my tap water?

Almost certainly yes, if you are brewing with chlorinated mains water — which covers most of the UK. Chlorine and chloramine are the main culprits behind the plastic, plaster or TCP off-flavours that brewing references tie to chlorophenols, and untreated water is one of the most common reasons a batch tastes “off”. At the very least, dechlorinate with a Campden tablet. The mineral and pH work beyond that is optional and style-dependent; the dechlorination step is close to non-negotiable for chlorinated supplies. If you brew with bottled or reverse-osmosis water, there is no chlorine to remove, but you may instead need to add some minerals back.

What is a Campden tablet for?

A Campden tablet is a pressed tablet of sodium (or potassium) metabisulphite. In home brewing its headline job is dechlorination: suppliers describe it as removing both chlorine and the more stubborn chloramine from tap water almost instantly, which standing or boiling cannot reliably do. The commonly quoted rate is one tablet per 20 gallons of water, so roughly half a tablet for a standard 23-litre batch. Crush it, stir it into fresh water before adding other ingredients, and wait a few minutes. The same tablets are also used in winemaking to inhibit wild yeast and oxidation, but for beer brewers the dechlorination role is the important one.

Gypsum or calcium chloride — which should I use?

It depends on the beer. Both add calcium, but gypsum brings sulphate while calcium chloride brings chloride, and those two ions pull flavour in opposite directions. Brewing references associate higher sulphate (gypsum) with a drier, sharper, more accentuated hop bitterness, making it the pick for pale ales, IPAs and hoppy or dry styles. Higher chloride (calcium chloride) is associated with a fuller, rounder, maltier mouthfeel, suiting stouts, milds, porters and sweeter bitters. Many brewers keep both and adjust the sulphate-to-chloride ratio per recipe, using a roughly 1:1 balance as a neutral starting point and tilting from there.

Do I need to worry about mash pH as a beginner?

Not on day one. If you are brewing kits or extract, the mash has already been done for you and pH is largely a non-issue. Even for early all-grain brews, dechlorinating your water and making sensible calcium additions will get you a long way. Mash pH becomes worth chasing once you want to tighten up efficiency and flavour, and the useful target that brewing references cite is around 5.2–5.6 measured at room temperature. When you do reach that stage, treat it as a measured process: use a calibrated pH meter or narrow-range strips and a water calculator, rather than dosing acid blind. Start with clean water and good calcium, and add pH control as your next step, not your first.