Patio & exterior
Patio Magic! dupe
Why pay around £24.99 for Patio Magic? The bulk active is Benzalkonium chloride (BAC 50) — 84% less per working litre than a typical shelf pack.
From the retail pack to the active and the mix
1 · Retail
Patio Magic!
5 litres · £24.99 typical snapshot
Water
2 · Active
Benzalkonium chloride
9.9% on the label
68424-85-1C22H40ClN
Bulk Benzalkonium chloride (BAC 50)
3 · Mix
1:4
£0.80 per working litre · 84% less than the shelf pack
- Active
- Benzalkonium chloride
- CAS
- 68424-85-1
- Dupe
- Benzalkonium chloride (BAC 50)
- Saving
- 84% / L
Saving is per litre of working-strength mix versus a typical pack price, not versus the DIY kit total. Shop prices move — always check the listing.
Label teardown
What the pack promises versus what the label chemistry actually is.
The marketing claim
“Kills algae, mould and lichens on patios, paths and roofs”
The chemical reality
Another BAC patio biocide in a different coloured bottle. Same quaternary ammonium as Wet & Forget; same bulk drum of BAC 50. You are paying for the brand, not a different molecule.
Active vs filler
9.9% Benzalkonium chloride · 90% carrier / filler — Water
- Typical retail
- £24.99
- 5 litres
- Estimated active cost
- £3.96
- Scaled from bulk £19.99 / 5 litres
- Indicative markup
- 6.3×
- Snapshot maths, not a live shop price
The Marketing Claim & The Catch
A 5 litres pack of Patio Magic! typically retails around £24.99 in patio & exterior. That is a UK shelf-price snapshot for the maths on this page — not a live shop quote or a manufacturer RRP. Listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: Kills algae, mould and lichens on patios, paths and roofs; One application, no rinsing; and Keeps working for months.
The catch: Another BAC patio biocide in a different coloured bottle. Same quaternary ammonium as Wet & Forget; same bulk drum of BAC 50. You are paying for the brand, not a different molecule.
- “Kills algae, mould and lichens on patios, paths and roofs”
- “One application, no rinsing”
- “Keeps working for months”
Proprietary Blend & Dosage Breakdown
The labelled active is Benzalkonium chloride at 9.9%. Everything else in the pack is water.
At 9.9% active, most of what you pay for is carrier and packaging. The brand is selling convenience, fragrance and a label — not a uniquely potent molecule.
Branded working strength is whatever comes out of the bottle. The bulk alternative is 50% Benzalkonium chloride (BAC 50), mixed to 1:4.
- Labelled active
- Benzalkonium chloride
- 9.9%
- Carrier
- Water
- Retail pack
- 5 litres · £24.99
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Benzalkonium chloride (BAC 50) at 50% bulk. Indexed as CAS 68424-85-1, formula C22H40ClN. Buy it as 5 litres for around £19.99 from Amazon UK.
Working strength: 1:4. Indicative cost £0.80 per diluted litre — 84% below a typical branded pack on a per-litre basis, before you reuse leftover bulk.
Follow the mixing method and the supplier SDS. Wear the listed PPE. Do not mix incompatible oxidisers, acids or ammonia.
- Wear nitrile gloves and splash goggles. Work outdoors.
- Patio Magic is sold at ~10% BAC. From BAC 50, mix 1 part concentrate with 4 parts water to land near that working strength.
- Apply to dry masonry until wet. Do not mix with bleach or acids.
- Leave to weather. Do not rinse. Keep pets off until dry.
- Repeat on persistent north-facing growth after two weeks.
Dilution recipe
5 L sprayer
Working strength 1:4. Educational estimate from the listed ratio — check the SDS before you mix.
Chemical
1,000 millilitres
Benzalkonium chloride (BAC 50)
Water
4 litres
Carrier / diluent
20% concentrate · 80% water by working volume (solids are dissolved into the water share).
Required PPE
Loading calculator…
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedPatio Magic | Raw active dupeDupeStack |
|---|---|---|
| Product | Patio Magic!Amazon UK search — listing, not a confirmed seller | Benzalkonium chloride (BAC 50) |
| Pack / unit | 5 litres · £24.99 | 5 litres · £19.99 |
| Active | Benzalkonium chloride at 9.9%Carrier: Water | 50% bulkC22H40ClN |
| CAS number | Not disclosed on pack | 68424-85-1 |
| Working strength | Ready-to-use pack | Dilute 1:4 |
| Cost per litre | £5.00 / L typical pack | £0.80 / L mixed from bulk |
| Headline saving | Baseline | 84% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene)Eye protection. Indirect-vent splash goggles — not ordinary spectaclesVentilation. Use outdoors or with mechanical extraction |
Active ingredient and cheaper alternative — FAQ
Is Patio Magic bleach?
No. Patio Magic is benzalkonium chloride (BAC), a quaternary ammonium biocide. Bleach is sodium hypochlorite. Never mix the two. For bleach-style black spot, see the Hagesan teardown — different chemistry.
What dilution matches Patio Magic from BAC 50?
Patio Magic is sold at about 10% BAC. From 50% concentrate, 1 part BAC 50 + 4 parts water lands near that bottle strength. Apply to dry masonry and leave to weather; do not rinse.
How do you mix the Patio Magic! dupe stack?
Wear nitrile gloves and splash goggles. Work outdoors. Patio Magic is sold at ~10% BAC. From BAC 50, mix 1 part concentrate with 4 parts water to land near that working strength. Apply to dry masonry until wet. Do not mix with bleach or acids. Leave to weather. Do not rinse. Keep pets off until dry. Repeat on persistent north-facing growth after two weeks.
DupeStack provides chemical concentration data and educational mixing guides only. Wellness pages compare food supplements, not medicines or prescribed treatments. Always review the supplier Safety Data Sheet (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Mixing and storage are at your own risk. Some links are affiliate advertisements (Amazon Associates, eBay Partner Network, and Awin when those programmes are live). Commissions do not change listed concentrations or calculator output.
Related guides
Patio guide
Patio cleaners decoded: BAC, DDAC, bleach, acid and degreasers
Which patio bottle is which molecule? Benzalkonium, DDAC, hypochlorite, brick acid, metasilicate, strippers and a silane sealer — matched to DupeStack teardowns.
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How much patio chemical do you need? Measure first
Convert a patio or drive into m², then into concentrate and water using DupeStack teardowns and the area estimator.
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Quat biocides, twin-chain DDAC and hypochlorite do different jobs on paving. When to use each — and what never to mix.
More teardowns
Patio & exterior
Wet & Forget Exterior Surface Cleaner
Wet & Forget
- Retail pack
- £34.005 litres
- Raw active
- Benzalkonium chloride (BAC 50)68424-85-1
A dilute quaternary ammonium biocide sold as a lifestyle patio product. The active is commodity BAC 50; the brand is paying for the trigger bottle and the television advert.
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
Hagesan Black Spot Remover
HG
- Retail pack
- £24.995 litres
- Raw active
- Sodium hypochlorite 14–15% (industrial / dairy grade)7681-52-9
Standard commercial bleach solution sold at five times agricultural merchant prices.
£44.97Save 84% / L
Indicative DIY stack