Start with the stain, not the colour of the bottle
Household ‘limescale removers’ are not one molecule. Kettle sachets, toilet gels, pink pastes and patio brick acid sit in different acid classes with different safe surfaces.
Limescale (calcium carbonate) → citric, sulfamic, lactic, acetic (vinegar) or formic (Viakal Classic spray) at label strength. Rust and tannin → oxalic or phosphoric. Toilet limescale under the rim → often stronger citric/sulfamic gels or ~9% hydrochloric (Harpic-style). Masonry cement haze → hydrochloric on acid-safe stone only — see the patio brick-acid teardown, not this guide.
Citric and sulfamic — descale without the fume
Citric acid monohydrate (CAS 5949-29-1) is the food-grade descaler in Cif cream, many kettle products and Dr. Beckmann Service-it liquid (about 7.5% in the 250 ml bottle — a drum descale, not a tap spray). Sulfamic acid (CAS 5329-14-6) is the plumber’s crystal descaler in Fernox DS-3 — stronger on stubborn scale, still less fuming than hydrochloric. Formic acid (CAS 64-18-6) is the punch in current Viakal Classic spray at about 3% plus a little citric — a bathroom trigger, not a kettle sachet; dilute 85% formic 1:27 and keep it off marble. Never pour the concentrate neat, and never mix with bleach.
Bulk citric or sulfamic plus water beats sachet tax for kettles, shower heads, washing-machine heaters and stainless sinks. Rinse food-contact surfaces well.
Lactic acid — the sachet descaler
Oust-style sachets are 70–90% lactic acid (CAS 50-21-5). One pour from a food-industry lactic jerry replaces a box of sachets. Same acid class as some ‘natural’ descalers — still an acid: gloves, ventilation, no bleach nearby.
Acetic acid — vinegar sprays
Astonish-style vinegar cleaners are acetic acid (CAS 64-19-7) at under 5% plus perfume. Diluting 80% acetic 1:19 matches that band — see the Astonish vinegar teardown. Still an acid: never mix with bleach, and keep off marble and limestone.
Oxalic and phosphoric — rust, not limescale
Oxalic acid (CAS 6153-56-6) bleaches rust and tannin — HG masonry rust, Bar Keepers Friend on pans. Phosphoric acid (CAS 7664-38-2) is two jobs: Jenolite-style rust conversion on steel, and HG Super Powerful foam (~30%) for bathroom limescale. Neither is a kettle descaler. Do not use on marble or limestone you care about.
Alkalis are a different aisle
Caustic drain gel (sodium hydroxide) and oven cleaner are bases, not acids. Soda crystals (sodium carbonate decahydrate) are a milder laundry alkali — grease-cutting and water-softening, not a drain unblocker. Bicarbonate of soda (CAS 144-55-8) is milder still — fridge odours and a paste scrub, not a hot-wash booster. Borax substitute is a different salt again: sodium sesquicarbonate, sitting between bicarbonate and washing soda — see the Dri-Pak bicarbonate and borax-substitute teardowns. Calgon 3-in-1 powder is zeolite 4A ion-exchange (CAS 1318-02-1), not citric and not soda crystals — an every-wash builder, not a kettle descale. Calgon 4-in-1 tabs are a different SKU: polycarboxylate / citrate sequesterant, not zeolite. Finish dishwasher salt is coarse sodium chloride (CAS 7647-14-5) for the machine’s ion-exchange resin — not citric descaler and not an electrolyte drink. Febreze-style fabric refresher is hydroxypropyl-β-cyclodextrin (CAS 128446-35-5), an odour trap, not an acid or a disinfectant. Jeyes Kleen Off is household ammonia (ammonium hydroxide, CAS 1336-21-6) — glass and grease, never mixed with bleach (chloramine). See the drain-and-oven guide for One Shot vs Mr Muscle vs Oven Pride. Never mix either side with bleach or the other side.
FAQ
- Is Cillit Bang the same as Fernox DS-3?
- Same job family (descaling) but different acids on the label. Cillit Bang limescale is often citric and/or sulfamic in a spray — Grease & Sparkle is a different bottle (LAS surfactant, not an acid). Viakal Classic spray is formic plus a little citric. Fernox DS-3 is solid sulfamic acid crystals. Oust sachets are mostly lactic acid. Astonish vinegar spray is acetic acid. Pick the teardown that matches the bottle you hold.
- Can I use brick acid in the kettle?
- No. Mortar Clen-style hydrochloric is for masonry cement haze — far too aggressive for kettles and food contact. Kettle descale is citric, sulfamic or lactic at food-safe dilutions.
- What must never be mixed?
- Acid + bleach = chlorine gas risk. Acid + caustic (sodium hydroxide) = violent heat. Different acids can be swapped only when the job and concentration match — not because both say ‘limescale’ on the front.
More household cleaning guides
Household guide
Drain and oven cleaners: sulphuric acid vs caustic soda — never swap blindly
Household guide
Disinfectants decoded: bleach, Dettol and hand gel — hypochlorite vs PCMX vs IPA
Household guide
Carpets and laundry stains: percarbonate vs machine surfactant
Household guide
Washing machines and dishwashers: Calgon, salt, citric and colour-run
Related teardowns
Live stacks this guide points at — mix maths and DIY affiliate links on each page.
Household cleaning
Cillit Bang Limescale Destroyer
Cillit Bang
- Retail pack
- £3.50750 millilitres
- Raw active
- Citric acid monohydrate (food grade)5949-29-1
Hard-water scale is calcium carbonate. Citric acid dissolves it. The trigger bottle is perfume and a nozzle; a bag of food-grade citric acid is the same attack on the kettle, the head and the pan.
Household cleaning
Classic Limescale Remover Spray
Viakal
- Retail pack
- £3.00500 millilitres
- Raw active
- Formic acid 85% (diluted to ~3%)64-18-6
Current UK Viakal Classic spray is formic acid (CAS 64-18-6) at about 1–5% plus citric at 1–5% — not Fernox sulfamic crystals and not Cillit Bang’s citric/sulfamic kitchen trigger. Dilute 85% formic 1:27 to the same ~3% band. Older professional Viakal listed sulfamic or maleic — read the SDS on the bottle you hold.
Household cleaning
Grease & Sparkle Power Cleaner
Cillit Bang
- Retail pack
- £3.50750 millilitres
- Raw active
- LAS 96% paste (linear alkylbenzene sulfonate)85536-14-7
This is not Cillit Bang Limescale. The grease trigger’s classified anionic on the kitchen-degreaser SDS is linear alkylbenzene sulfonate (LAS, CAS 85536-14-7) at under 3%. Fairy is SLES — a different sulphate. Dilute LAS 96% paste to about 3% and you have the same grease-cut without the orange-bottle tax.
Household cleaning
All Purpose Descaler Sachets
Oust
- Retail pack
- £3.5075 millilitres (3 × 25 ml sachets)
- Raw active
- Lactic acid 80% (food / technical)79-33-4
This is not citric acid and it is not sulfamic. The sachet is 70–90% lactic acid — the same food-industry acid sold in 1 litre jerry cans. One 25 ml pour descale a kettle; three sachets is a tiny pour from that jerry.
Household cleaning
DS-3 Cleaner Descaler
Fernox
- Retail pack
- £14.50500 g tub
- Raw active
- Sulfamic acid 99% (sulphamic acid crystals)5329-14-6
Sulfamic acid is the plumber’s descaler: a solid, less fuming than hydrochloric, stronger on scale than citric. The 500 g Fernox tub is a labelled bag of the same 99% crystals sold in 1 kg jars for a kettle-and-combi DIY stack.
Household cleaning
White Vinegar Multi-Purpose Cleaner
Astonish
- Retail pack
- £1.30750 millilitres
- Raw active
- Acetic acid 80% (diluted to ~4.5% w/v)64-19-7
Astonish’s vinegar spray is acetic acid (CAS 64-19-7) at under 5% plus a drop of surfactant and perfume. Diluting 80% acetic acid 1:19 lands in the same band as the trigger bottle — without the citrus markup. This is not citric (Cillit Bang / Cif) and not soda crystals.
Patio & exterior
HG Rust Stain Remover
HG
- Retail pack
- £8.50500 millilitres
- Raw active
- Oxalic acid dihydrate6153-56-6
Oxalic acid is the classic rust and tannin bleach for masonry. HG bottles a dilute solution; a kilogram of crystals makes tens of litres of the same chemistry.
Patio & exterior
Rust Remover Gel
Jenolite
- Retail pack
- £8.99500 millilitres
- Raw active
- Phosphoric acid 81% (food / technical) diluted to ~25%7664-38-2
This is not oxalic (that is HG masonry rust) and it is not hydrochloric (Mortar Clen). Phosphoric acid etches rust to iron phosphate. Technical 81% phosphoric diluted to about 25% is the same attack without the gel tax. Keep it off limestone.
Household cleaning
Limescale Remover Foam Spray Super Powerful
HG
- Retail pack
- £6.50500 millilitres
- Raw active
- Phosphoric acid 81% (food / technical) diluted to ~30%7664-38-2
HG Super Powerful foam is phosphoric acid at about 30% w/w — a bathroom descale, not Jenolite rust gel and not citric kettle sachets. Dilute 81% food-grade phosphoric 1:1.7 to the same band. Keep it off marble and never mix it with bleach.
Household cleaning
Cleanser & Polish
Bar Keepers Friend
- Retail pack
- £2.50250 grams
- Raw active
- Oxalic acid dihydrate6153-56-6
Bar Keepers Friend is oxalic acid plus a mild abrasive — the same rust-busting chemistry as HG patio rust remover, repackaged for the kitchen. Oxalic dihydrate crystals and bicarbonate paste do the job without the pink can.
Household cleaning
Cream Cleaner
Cif
- Retail pack
- £1.50500 millilitres
- Raw active
- Citric acid monohydrate + calcium carbonate5949-29-1
Cif is citric acid plus a mild limestone abrasive in a cream base — the same soft scrub as mixing food-grade citric with chalk. The Pink Stuff is quartz abrasive instead; Cif is acid-forward for limescale film.
Household cleaning
Power Plus Original
Harpic
- Retail pack
- £2.50750 ml bottle
- Raw active
- Technical hydrochloric acid 32–36% diluted to toilet strength7647-01-0
Nine grams of hydrochloric acid per 100 g of liquid — toilet limescale and uric scale, not patio brick acid. The same HCl family as Mortar Clen but far weaker and formulated for ceramic WC pans. Dilute 30–36% pool-grade HCl carefully to a similar working strength, or buy labelled toilet acid once and compare the SDS.
Household cleaning
Soda Crystals
Dri-Pak
- Retail pack
- £2.491 kg
- Raw active
- Sodium carbonate decahydrate (soda crystals)6132-02-1
Dri-Pak’s bag is sodium carbonate decahydrate (CAS 6132-02-1) — washing soda. The molecule is the product. A 5 kg sack of the same crystals is the cupboard staple without the 1 kg grocery markup. This is not Vanish (that is percarbonate) and not borax substitute (sesquicarbonate).
Household cleaning
Borax Substitute
Dri-Pak
- Retail pack
- £2.99500 grams
- Raw active
- Sodium sesquicarbonate (borax substitute)533-96-0
Borax substitute is sodium sesquicarbonate (CAS 533-96-0) — not borax, not soda crystals, not bicarbonate. Dri-Pak’s 500 g box is a grocery pour of the same salt sold in 5 kg sacks. The EU reclassified borates; this is the carbonate/bicarbonate double salt that replaced the cupboard staple.
Household cleaning
Bicarbonate of Soda
Dri-Pak
- Retail pack
- £1.99500 grams
- Raw active
- Sodium bicarbonate (food-grade bicarbonate of soda)144-55-8
Dri-Pak’s 500 g box is sodium bicarbonate (CAS 144-55-8) — baking soda. The molecule is the product. A 5 kg sack of the same food-grade powder is the cupboard staple without the grocery-box markup. This is not soda crystals (carbonate) and not borax substitute (sesquicarbonate).
Household cleaning
Service-it Washing Machine Cleaner
Dr. Beckmann
- Retail pack
- £3.50250 millilitres
- Raw active
- Citric acid monohydrate (food grade)5949-29-1
The liquid Service-it bottle is 5–10% citric acid — a kettle descaler poured into an empty drum. Food-grade citric at about 75 g/L is the same heater-and-door-seal wash without the 250 ml appliance-aisle tax. This is not the powder Deep Clean (that is percarbonate — see Vanish).
Household cleaning
3 in 1 Limescale Protection Powder
Calgon
- Retail pack
- £3.50500 grams
- Raw active
- Detergent-grade zeolite 4A (sodium aluminosilicate)1318-02-1
Calgon 3-in-1 powder is mostly zeolite 4A (CAS 1318-02-1) — a detergent ion-exchange builder, not citric acid and not soda crystals. The box lists more than 30% zeolites plus a pinch of polycarboxylate and perfume. A 5 kg sack of detergent-grade 4A is the same softening mineral. This is not pond clinoptilolite and not a kettle descaler.
Household cleaning
4-in-1 Limescale Protection Tablets
Calgon
- Retail pack
- £10.50390 grams (30 tablets)
- Raw active
- Trisodium citrate dihydrate (food grade)6132-04-3
Current Calgon 4-in-1 tabs declare 15–30% polycarboxylates (sodium polyacrylate family, CAS 9003-04-7) plus perfume. Older Express tabs also listed sodium citrate. The everyday hardness job is a teaspoon of food-grade trisodium citrate — not a monthly citric drum descale (that is Service-it).
Household cleaning
Dishwasher Salt
Finish
- Retail pack
- £4.502 kg
- Raw active
- PDV / water-softener salt (sodium chloride, coarse)7647-14-5
Finish dishwasher salt is sodium chloride (CAS 7647-14-5) — coarse, high-purity salt for the machine’s ion-exchange softener. The molecule is the product. A 25 kg sack of PDV or water-softener salt is the same regenerant without the 2 kg grocery-box tax. This is not tablet detergent, not rinse aid, and not table salt (anti-caking agents can clog the softener).
Household cleaning
Fabric Refresher
Febreze
- Retail pack
- £3.50500 millilitres
- Raw active
- Hydroxypropyl-β-cyclodextrin (HP-β-CD)128446-35-5
The odour trap in Febreze fabric spray is hydroxypropyl-β-cyclodextrin (CAS 128446-35-5) at about 1% — a sugar ring that hosts smelly molecules. The television advert is the perfume. A 1% cyclodextrin wipe is the same host chemistry without the Unstopables tax. It is not a disinfectant and it is not bicarbonate in a trigger.
Household cleaning
Kleen Off Ammonia Multi-Purpose Cleaner
Jeyes
- Retail pack
- £2.49500 millilitres
- Raw active
- Household ammonia 9–10% (ammonium hydroxide)1336-21-6
UK Windolene is no longer ammonia. Kleen Off still is: a ~9–10% ammonium hydroxide solution in a 500 ml bottle. A 5 litre jerry of 10% household ammonia is the same molecule. Never mix it with bleach. The catch is the fumes, not a secret surfactant.
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