Consumer advocacy teardown
Wet & Forget Exterior Surface Cleaner alternative & active ingredient dupe
Stop paying £34.00 for Wet & Forget. The bulk active is Benzalkonium chloride (BAC 50) — 88% less per working litre than a typical pack.
- Active
- Benzalkonium chloride
- CAS
- 68424-85-1
- Dupe
- Benzalkonium chloride (BAC 50)
- Saving
- 88% / 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.
The Marketing Claim & The Catch
A typical 5 litres pack of Wet & Forget Exterior Surface Cleaner is about £34.00 in patio & exterior. That is a snapshot, not a live Amazon price — listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: No scrubbing, no pressure washing — just spray and walk away; Kills mould, algae, lichen and mildew on exterior surfaces; and Bleach-free formula that keeps working in the rain.
The catch: 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.
- “No scrubbing, no pressure washing — just spray and walk away”
- “Kills mould, algae, lichen and mildew on exterior surfaces”
- “Bleach-free formula that keeps working in the rain”
Proprietary Blend & Dosage Breakdown
The labelled active is Benzalkonium chloride at 8%. Everything else in the pack is water.
At 8% 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 1:9.
- Labelled active
- Benzalkonium chloride
- 8%
- Carrier
- Water
- Retail pack
- 5 litres · £34.00
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 about £19.99 from Amazon UK.
Working strength: 1:9. Indicative cost £0.40 per diluted litre — 88% 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.
- Put on nitrile gloves and splash goggles before opening the concentrate.
- Work outdoors or in a well-ventilated area. Do not mix with bleach, acids or anionic detergents.
- Measure 1 part BAC 50 into a clean sprayer, then add 9 parts water (e.g. 500 ml concentrate + 4.5 L water for a 5 L sprayer).
- Invert gently to mix. Apply to a dry patio until surfaces glisten; do not rinse.
- Leave to weather. Algae and lichen typically collapse over 2–7 days. Repeat on north-facing stone if needed.
Mixing desk
Dilution calculator
Switch between filling a sprayer and covering a measured surface. Figures are educational estimates from the listed ratio — always check the SDS.
Formula
Benzalkonium chloride (BAC 50)
- Concentrate
- 500 ml
- millilitres of liquid
- Water
- 4.5 L
- carrier volume
- Batch cost
- £2.00
- 5 L working solution
- Saved vs retail
- £32.00
- 94% · retail £34.00
Estimated coverage at the listed rate: 25 m².
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedWet & Forget | Raw active dupeDupeStack |
|---|---|---|
| Product | Wet & Forget Exterior Surface CleanerAmazon UK search — listing, not a confirmed seller | Benzalkonium chloride (BAC 50) |
| Pack / unit | 5 litres · £34.00 | 5 litres · £19.99 |
| Active | Benzalkonium chloride at 8%Carrier: Water | 50% bulkC22H40ClN |
| CAS number | Not disclosed on pack | 68424-85-1 |
| Working strength | Ready-to-use pack | Dilute 1:9 |
| Cost per litre | £6.80 / L typical pack | £0.40 / L mixed from bulk |
| Headline saving | Baseline | 88% 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
What is the active ingredient in Wet & Forget?
Wet & Forget Exterior Surface Cleaner is labelled as Benzalkonium chloride at 8%. The carrier is Water. Pack size: 5 litres. The bulk equivalent we index is Benzalkonium chloride (BAC 50) (CAS 68424-85-1).
Is Benzalkonium chloride (BAC 50) safe on paving?
Used at the listed working strength (1:9), the dupe is the same chemistry as the branded pack for paving, porcelain and masonry. That is not a blanket all-clear: read the supplier SDS, wear the listed PPE, keep acids away from hypochlorite, and follow UK HSE/COSHH rules. Wellness teardowns are supplements, not medicines.
Is there a cheaper alternative to Wet & Forget Exterior Surface Cleaner?
Yes. The bulk equivalent is Benzalkonium chloride (BAC 50) (CAS 68424-85-1). Indicative saving 88% per working litre versus a typical £34.00 pack. Working strength: 1:9. Live shop prices move.
How do you mix the Wet & Forget Exterior Surface Cleaner dupe stack?
Put on nitrile gloves and splash goggles before opening the concentrate. Work outdoors or in a well-ventilated area. Do not mix with bleach, acids or anionic detergents. Measure 1 part BAC 50 into a clean sprayer, then add 9 parts water (e.g. 500 ml concentrate + 4.5 L water for a 5 L sprayer). Invert gently to mix. Apply to a dry patio until surfaces glisten; do not rinse. Leave to weather. Algae and lichen typically collapse over 2–7 days. Repeat on north-facing stone if needed.
DupeStack provides chemical concentration data and educational mixing guides. Always review official manufacturer Safety Data Sheets (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Some links on this site are affiliate links.
More teardowns
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- Retail pack
- £24.995 litres
- Raw active
- Benzalkonium chloride (BAC 50)68424-85-1
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- Retail pack
- £8.50500 millilitres
- Raw active
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Hagesan Black Spot Remover
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- 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.
DIY stack · 88% / L vs branded
£44.97indicative kit · Amazon cannot add a mixed search kit as one basket