Three different chemistries
BAC (benzalkonium chloride) and DDAC (didecyldimethylammonium chloride) are quaternary ammonium biocides — they collapse algae and soft green film when left to weather in. Hypochlorite (bleach) is an oxidiser — it attacks organic colour fast on some jobs (black spot, mouldy film) but is not the same mechanism as a walk-away quat. Sodium percarbonate (Logco Eco patio powder) is a third oxidiser — a solid peroxide adduct you dissolve, scrub and rinse, not a leave-on biocide.
Neither quat nor bleach removes cement smears (acid), oily concrete (alkaline degreaser), or old sealer (solvent stripper). Pick the molecule for the stain.
When to choose BAC
Wet & Forget and Patio Magic are BAC-family products. Typical use: dry patio, spray until wet, leave to weather. Good for general green algae and soft growth on paths that tolerate a quat label.
Bulk stack: BAC 50 diluted to the working strength on your chosen teardown — usually a much higher dilution than the small print on the bottle suggests.
When to choose DDAC
Jeyes 4-in-1 Patio Power is labelled DDAC, not BAC. Same broad job (algae film) but different quat and different dilution maths. Do not assume it swaps 1:1 with Patio Magic.
If the SDS says DDAC, use the DDAC teardown dilution — not the BAC drum.
When to choose hypochlorite
HG Hagesan-style black spot removers use hypochlorite (~14% in the branded concentrate). Useful when quats have not shifted stubborn black lichen dots — but test on a hidden patch first. Rinse plants and keep pets off.
Domestos-style ~5% hypochlorite is a different strength class — not a straight substitute for a patio black-spot concentrate without redoing the maths. Percarbonate oxygen powder is milder and needs a dwell-and-scrub; see the Logco Eco teardown.
Never mix
Quat + bleach = dangerous chlorine release risk. Acid + bleach = chlorine gas risk. Percarbonate + hypochlorite is a wasted oxidiser fight. Acid + alkaline degreaser = heat and splatter. One product, one wash, thorough rinse if you change approach.
FAQ
- Can I mix Patio Magic with Jeyes 4-in-1?
- No. Patio Magic is BAC; Jeyes 4-in-1 is DDAC. Both are quats, but you still should not mix biocide products with each other, with bleach, or with anionic washing-up liquid.
- Will bleach work like Wet & Forget?
- Hypochlorite oxidises organic growth quickly on some surfaces but behaves differently from a leave-on quat. It is not a drop-in substitute for BAC on every stone type, and you must never mix bleach with quat biocides or acids.
More patio & exterior guides
Patio guide
Patio cleaners decoded: BAC, DDAC, bleach, acid and degreasers
Patio guide
How much patio chemical do you need? Measure first
Patio guide
When to use a metasilicate degreaser on driveways
Patio guide
Driveway oil stains: degreaser vs solvent vs absorbent
Patio guide
Water-repellent, biocide or acid — which patio job needs which chemistry
Patio guide
Driveway & TFR oil and grease: which solvent for which stain
Related teardowns
Live stacks this guide points at — mix maths and DIY affiliate links on each page.
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
Patio Magic!
Patio Magic
- Retail pack
- £24.995 litres
- Raw active
- Benzalkonium chloride (BAC 50)68424-85-1
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.
Patio & exterior
4-in-1 Patio Power
Jeyes
- Retail pack
- £16.004 litres
- Raw active
- Didecyldimethylammonium chloride (DDAC 50)7173-51-5
This is not old Jeyes Fluid (tar acids are gone). Patio Power is 1.75% DDAC — a twin-chain quat, not the benzalkonium in Patio Magic. Dilute DDAC 50 to about 0.35% and you have the same working spray as the 4 L bottle mixed 1+4.
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.
Patio & exterior
Patio, Driveway & Masonry Cleaner
KilrockPRO
- Retail pack
- £14.005 litres
- Raw active
- Sodium metasilicate pentahydrate10213-79-3
This is not Patio Magic (BAC) and it is not Mortar Clen (HCl). KilrockPRO is a dilute alkaline masonry degreaser — disodium metasilicate (CAS 6834-92-0) with soda ash and a chelator. Metasilicate pentahydrate crystals mixed at about 30 g/L match the bottle strength; then dilute 1:20 for light stains as the pack does.
Household cleaning
Domestos Original Thick Bleach
Domestos
- Retail pack
- £2.20750 millilitres
- Raw active
- Household thin bleach (sodium hypochlorite ~5%)7681-52-9
Sodium hypochlorite plus a thickener so it clings to ceramic. Thin household bleach is the same oxidiser without the brand, the dye and the TV campaign. Never mix it with acids or ammonia.
Patio & exterior
Mortar Clen Brick & Patio Acid
Everbuild
- Retail pack
- £16.505 litres
- Raw active
- Technical hydrochloric acid 32–36%7647-01-0
Retail brick acid is technical hydrochloric acid cut to about 9%. 5 litres of 36% acid plus 15 litres of water is 20 litres of the same working strength.
Patio & exterior
Eco Patio & Decking Cleaner
Logco
- Retail pack
- £29.995 kg tub
- Raw active
- Sodium percarbonate (technical oxygen bleach)15630-89-4
Logco’s Eco patio powder is sodium percarbonate (CAS 15630-89-4) — the same solid peroxide adduct as Vanish Oxi, sold as a 5 kg outdoor tub. Fifty grams per litre of warm water is the deck/patio band (about 5 m²/L). It is not BAC, not DDAC and not hypochlorite. A technical 5 kg sack is the same oxidiser without the decking label.
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