ChloroKlean BPR Compliant Chlorine Dioxide Disinfectant - UK Supplier

Chlorine Dioxide vs Sodium Hypochlorite for Legionella Control

Chlorine dioxide (ClO₂) and sodium hypochlorite (NaOCl, common bleach) are both chlorine-based oxidising biocides used for Legionella control and general water disinfection. Sodium hypochlorite is cheap and familiar but has well-documented limitations: its biocidal form (hypochlorous acid, HOCl) only dominates below pH 7.5, it reacts with ammonia to form chloramines and with organics to form trihalomethanes (THMs) and haloacetic acids (HAAs), and it cannot penetrate established biofilm. Effective dose rates are therefore high (2-4 ppm free chlorine residual). Chlorine dioxide is effective across pH 4-10 with no loss of biocidal action, does not form THMs or chloramines, penetrates biofilm in pipework, and achieves >4-log Legionella reduction at residuals as low as 0.1-0.5 ppm. For UK water systems regulated under ACoP L8 and HSG274, ClO₂ provides a more reliable, lower-dose route to compliance. ChloroKlean Plus L20 is BPR-compliant for PT5 (potable water) and PT11 (cooling systems).

Author
Key Advantage of ClO₂
Works across pH 4-10, penetrates biofilm, achieves Legionella control at 0.1-0.5 ppm where hypochlorite needs 2-4 ppm.
By-products
ClO₂ produces no THMs, HAAs, or chloramines at typical doses. Sodium hypochlorite forms chloramines, THMs, HAAs, and chlorates - several are regulated by the DWI and WHO.
pH Range
ClO₂ effective at pH 4-10 with no loss of biocidal activity. Hypochlorite loses >50% efficacy above pH 7.5 as HOCl shifts to OCl⁻.
Regulatory Sources
HSE ACoP L8, HSE HSG274 Parts 1-3, DWI Regulation 31, WHO Guidelines for Drinking-water Quality, EU BPR 528/2012 PT5/PT11
UK Compliance
Both are widely used under UK GB BPR. ChloroKlean Plus L20 holds PT5/PT11 compliance. Hypochlorite is also PT5/PT11 listed but requires higher residual to meet ACoP L8 Legionella targets.
Comparison Guide

Chlorine Dioxide vs Sodium Hypochlorite

Sodium hypochlorite (bleach) is the cheapest chlorine source - but it loses efficacy above pH 7.5, reacts with ammonia and organics, forms regulated by-products, and cannot penetrate biofilm. ClO₂ solves all four problems at sub-ppm doses.

ClO₂

Chlorine Dioxide

  • Effective pH 4-10 - works in real-world water systems
  • Penetrates biofilm where Legionella harbours
  • No THMs, HAAs, or chloramines at dosing rates
  • 0.1-0.5 ppm residual sufficient for ACoP L8 compliance
  • Does not react with ammonia or organics in mains water
NaOCl

Sodium Hypochlorite

  • Low chemical cost per litre
  • Familiar to operators, widely available
  • Loses biocidal efficacy above pH 7.5
  • Forms THMs, HAAs, chloramines from organics
  • Cannot penetrate established biofilm

Detailed Comparison

Detailed comparison of chlorine dioxide versus sodium hypochlorite
FeatureChlorine DioxideSodium Hypochlorite
Effective Dose for Legionella

0.1-0.5 ppm

Sub-ppm residual achieves >4-log reduction

2-4 ppm

Higher residual needed; often loses to demand

pH Range Effectiveness

pH 4-10

Biocidal activity independent of pH

Optimal pH <7.5

>50% efficacy lost as HOCl shifts to OCl⁻

Biofilm Penetration

Excellent

Diffuses into and oxidises EPS matrix

Poor

Reacts at biofilm surface only

THM / HAA Formation

None at dose

Does not chlorinate organics

Yes

Regulated DBPs under DWI and US EPA rules

Chloramine Formation

None

Does not react with ammonia

Yes

Reacts with ammonia; loses free chlorine

Reaction with Organic Demand

Low

Selective oxidiser; survives demand

High

Demand consumes free chlorine rapidly

Dosing Accuracy

Precise

Sub-ppm dosing via metering pump

Variable

Residual fluctuates with demand and pH

Material Compatibility

Good

Compatible with stainless and most plastics

Corrosive

Attacks rubber, EPDM, mild steel

UK BPR Status

PT5/PT11 Compliant

Full GB BPR compliance

PT5/PT11 Listed

Also BPR-listed active substance

When to Choose Each

Choose Chlorine Dioxide When:

  • Legionella control under ACoP L8 / HSG274 is required
  • Existing biofilm is documented or suspected
  • Water pH runs above 7.5 (most UK potable supplies)
  • Source water has measurable ammonia or organic demand
  • THM / HAA compliance is marginal at the tap
  • Lower chemical use is required for sustainability or cost

Consider Sodium Hypochlorite When:

  • One-off shock treatment of a new or drained system
  • Lowest-cost basic disinfection of clear, low-demand water
  • Existing dosing infrastructure cannot be changed short-term
  • Used as a backup or emergency biocide alongside ClO₂
  • Local site policy mandates a free chlorine residual
"In ACoP L8 audits we see the same pattern again and again - a hypochlorite-dosed system with the right total chlorine residual on paper, but biofilm fouling at every dead leg and Legionella counts that refuse to come down. Hypochlorite is reacting at the biofilm surface and being consumed before it can penetrate. Switching to chlorine dioxide at 0.3 ppm typically clears that biofilm within weeks. The maths is simple: less chemical, more biocide where it matters."
GO

Gavin Owen, Managing Director, ChloroKlean

BPR-compliant disinfection specialist

Why Choose ChloroKlean Plus L20

If you're considering switching to chlorine dioxide, ChloroKlean Plus L20 is purpose-built for industrial and commercial applications.

BPR PT5 / PT11 Compliant

ChloroKlean Plus L20 holds GB BPR compliance for drinking water (PT5) and cooling system preservation (PT11). Direct replacement for hypochlorite in potable and process water.

Stabilised Liquid Formulation

Regenerative chemistry means no on-site generator and no chlorite/chlorate handling. Dose with a standard metering pump - simpler infrastructure than two-part ClO₂ generators.

ACoP L8 Field Results

Case studies in hospitals, cooling towers, and leisure facilities show sustained Legionella control where hypochlorite failed. >4-log reduction documented under BS EN 13623:2020.

Regulatory and Scientific References

This comparison is informed by the following authoritative sources. Always refer to the latest published guidance.

HSE ACoP L8
Health and Safety Executive (HSE)

Legionnaires' disease: The control of legionella bacteria in water systems

ACoP L8 is the Approved Code of Practice for Legionella control in UK water systems. It requires effective biocide residual and biofilm management - areas where ClO₂ outperforms hypochlorite.

View source
HSE HSG274
Health and Safety Executive (HSE)

Legionella: Technical guidance Parts 1, 2 and 3

HSG274 sets technical detail for cooling towers (Part 1), hot and cold water (Part 2), and other risk systems (Part 3). All parts emphasise biofilm control as a Legionella management priority.

View source
DWI Regulation 31
Drinking Water Inspectorate (DWI)

Approval of products and substances for use in public water supply

DWI Regulation 31 controls which chemicals can be used in UK public water supply. Both hypochlorite and approved chlorine dioxide products are listed; THM compliance under the Water Supply (Water Quality) Regulations remains the operator's responsibility.

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WHO Guidelines
World Health Organization (WHO)

Guidelines for Drinking-water Quality (Chlorine and Chlorine Dioxide)

WHO compares chlorine and chlorine dioxide as drinking water disinfectants, noting ClO₂'s pH independence, lower DBP formation, and effectiveness against Cryptosporidium.

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US EPA D/DBPR
US Environmental Protection Agency

Disinfectants and Disinfection Byproducts Rules

EPA sets enforceable limits on THMs (80 µg/L), HAA5 (60 µg/L), and chlorite (1.0 mg/L). Switching to ClO₂ commonly reduces THM and HAA formation in distribution.

View source

Frequently Asked Questions

Move from Hypochlorite to Compliant ClO₂ Dosing

ChloroKlean Plus L20 delivers ACoP L8 / HSG274 Legionella control at 0.1-0.5 ppm - with no THMs, no chloramines, and proven biofilm penetration.