ChloroKlean Plus L20 Dosing Guide
Practical dose rates, contact times, and monitoring targets for the most common ChloroKlean Plus L20 applications. Use alongside the product TDS and the written scheme of treatment for the system.
ChloroKlean Plus L20 is a single-pack regenerative chlorine dioxide product authorised under GB BPR for PT2 pools and spas, PT4 food contact surfaces, PT5 drinking water, and PT11 cooling systems. This page sets out indicative dose and monitoring guidance for each application. It is not a substitute for the product Technical Data Sheet or the written scheme of treatment for the specific system - it is a starting point for technical assessment.
How Dose Rate Is Calculated
Dose rate for ChloroKlean Plus L20 is calculated to maintain a target free ClO2 residual at the furthest point from the dose entry, not at the dose point. That is what determines whether the system is being treated end to end.
The three inputs are: system volume (litres), turnover rate (volume turned over per hour), and measured ClO2 demand (the dose lost to organic load and biofilm in the loop). Demand is established by a short trial; assume higher demand on first-fill or commissioning, then steady state once biofilm is under control.
For initial sizing, use the indicative dose rates below for the application. Always confirm the actual dose with residual monitoring at distal points within the first treatment cycle.
Pools and Spas (PT2)
For domestic and small commercial spas: dose to maintain 0.1 to 0.3 ppm free ClO2. Initial fill dose typically 5 to 15 ml of ChloroKlean Plus L20 per 1000 litres depending on water condition. Maintain residual continuously and test at least daily during use.
For larger commercial pools and PSPC-compliant facilities: dose to maintain 0.2 to 0.4 ppm free ClO2, calculated against bather load. Continuous automatic dosing is recommended. Sample at multiple distal points to confirm coverage of the whole circulation loop.
ClO2 does not form chloramines, so eye and respiratory irritation typical of chlorine pools is not seen at recommended doses. pH window is wider than chlorine but routine pH monitoring should still be in place for water balance and bather comfort.
Cooling Towers and Evaporative Condensers (PT11)
Indicative starting dose: 0.2 to 0.5 ppm free ClO2 maintained continuously at distal points. Calculate dose volume against system holding volume and recirculation rate. Allow for higher demand during commissioning or after a system clean.
Monitoring regime: free ClO2 residual at distal points and in the recirculating loop daily during commissioning, weekly once stable. Microbiology (Legionella and TVC) sampling per the written scheme of treatment. Trend data should show a flat residual curve, not a sawtooth.
Where existing biofilm is present, a short higher-dose pass at 1 to 2 ppm may be used at the start of the programme to break down the biofilm matrix, before settling to sustained sub-0.5 ppm residual.
Drinking Water and PT5 Applications
Dose to maintain residual within Drinking Water Inspectorate guideline limits. For most PT5 applications a target of 0.1 to 0.3 ppm free ClO2 at the point of use is appropriate, with consideration of chlorite and chlorate limits in finished water.
Monitor residual at multiple distal points and at the point of use. Where the system has any reach to retail or domestic supply, the operator must have a competent water treatment specialist and an agreed monitoring regime.
For backflow from secondary use into the wholesome supply, refer to the Water Supply (Water Fittings) Regulations and the relevant water company's risk fluid category guidance.
Food Contact Surfaces and CIP (PT4)
Indicative dose for food contact surface disinfection: 100 to 250 ppm ClO2 working solution with 5 to 10 minute contact time, followed by potable water rinse where required by the application. Follow the product TDS for the specific food sector.
For Clean-in-Place (CIP) loops in beverage and dairy applications, doses are calculated against the cleaning cycle time, target log reduction, and the surface biofilm risk. Validation against HACCP critical control points is required.
Operator PPE for handling concentrate at make-up dilution is mandatory in line with the Safety Data Sheet.
Key Data & Statistics
<0.5ppm
Typical continuous dose for cooling system Legionella control
0.1-0.3ppm
Target residual for PT2 pool and spa applications
PT2/4/5/11
GB BPR product types L20 is authorised under
4-10
pH range across which dosing remains effective
Indicative ChloroKlean Plus L20 Doses by Application
Starting-point dose ranges for the four main BPR product types ChloroKlean Plus L20 is authorised under.
| Feature | Application | Target Residual | Indicative Dose | Monitoring |
|---|---|---|---|---|
| Spa / small commercial pool (PT2) | 0.1-0.3 ppm ClO2 | 5-15 ml per 1000 L initial fill | Daily distal residual | |
| Commercial pool (PT2) | 0.2-0.4 ppm ClO2 | Continuous automatic dose | Multi-point distal residual | |
| Cooling tower (PT11) | 0.2-0.5 ppm ClO2 | Continuous, sized to loop volume | Daily during commissioning, weekly steady-state | |
| Potable water (PT5) | 0.1-0.3 ppm ClO2 | Continuous, sized to DWI limits | Per written scheme | |
| Food contact surfaces (PT4) | 100-250 ppm working solution | Make-up dilution from concentrate | Validated per HACCP CCP |
All figures are indicative starting points. Confirm against product TDS and written scheme of treatment for the specific system.
How to Set the Dose Rate for a New Application
Repeatable sequence for sizing a ChloroKlean Plus L20 dose against the system being treated.
Confirm Application and Authorised Product Type
Match the application to the relevant GB BPR PT for ChloroKlean Plus L20 (PT2, PT4, PT5, or PT11). Pull the SDS and TDS.
Establish System Volume and Turnover
Calculate the system volume in litres and the recirculation rate or turnover in volumes per hour. For pools and spas this comes from the pool plant design. For cooling towers, from the recirculation pump rating and cycles of concentration.
Set Initial Target Residual
Use the indicative target residual for the application from this guide as a starting point. Calculate the initial dose volume needed to achieve that target across the system volume.
Run a 7-Day Demand Test
Dose at the initial rate. Monitor free ClO2 residual at distal points twice daily. Adjust dose until the residual at the furthest point holds steady at the target value.
Document and Continue Monitoring
Record the steady-state dose rate, monitoring frequency, and acceptance criteria in the written scheme of treatment. Continue residual monitoring per the scheme; review trend data monthly.
Expert Insights
"Dose the distal point, not the dose point. If the residual at the far end of the loop is at target, the whole loop is being treated. If it is not, you are dosing into a dead leg."
Gavin Owen
Managing Director, ChloroKlean
"Most dosing problems are biofilm problems. Run a short higher-dose pass to break the biofilm matrix, then settle into sustained sub-0.5 ppm dosing. Chasing the bug count with higher continuous dose almost never works."
Gavin Owen
Managing Director, ChloroKlean
About the Reviewer
Gavin Owen
Managing Director, ChloroKlean
Gavin Owen leads ChloroKlean's technical and commercial operations, bringing over 20 years of experience in industrial chemical distribution and water treatment. He oversees product development, regulatory compliance strategy, and the company's BPR compliance programme across PT2, PT4, PT5, and PT11 product types. Gavin works directly with water treatment professionals, facilities managers, and public health engineers across healthcare, leisure, food processing, and industrial sectors.
Related Products
BPR-compliant chlorine dioxide products available from ChloroKlean.
Frequently Asked Questions
Common questions about this topic, answered by our technical team.
Important Safety Information
- ChloroKlean Plus L20 concentrate is a hazardous oxidiser. PPE per the Safety Data Sheet is required for handling.
- Do not mix the concentrate with other chemicals outside the documented dosing programme.
- All dose figures on this page are indicative starting points. Always confirm against the product TDS and the written scheme of treatment for the specific system.
- Residuals in potable water must remain within DWI and WHO guideline limits for ClO2, chlorite, and chlorate.
- Operators of systems within scope of ACOP L8 must maintain a written scheme of treatment, risk assessment, and competent person oversight.
This guide is technical guidance only. It does not replace the product Safety Data Sheet, Technical Data Sheet, COSHH assessment, or the written scheme of treatment for the system being dosed.
Related Resources
Continue exploring our knowledge base and product information.
Regenerative Chlorine Dioxide Explained
The chemistry behind sustained ClO2 residual.
Chlorine Dioxide vs Chlorine for Cooling Towers
Side-by-side comparison for HSG274-scope systems.
Legionella Control ACOP L8 Guide
How dose decisions fit into the written scheme of treatment.
Auto-Dosing Systems
Continuous dose hardware for pools, spas, and process water.
Safe Use Guide
PPE, storage, first aid, and COSHH-compliant handling for ChloroKlean concentrate.
Contact Technical Support
Get dosing calculations and product selection support from ChloroKlean's technical team.
Sources & References
This article references guidance from the following authoritative sources:
- ACOP L8: Legionnaires' disease - Control of legionella bacteria in water systems
HSE - Health and Safety Executive
- HSG274 Part 1: The control of legionella bacteria in evaporative cooling systems
HSE - Health and Safety Executive
- HSG274 Part 2: The control of legionella bacteria in hot and cold water systems
HSE - Health and Safety Executive
- Guidelines for Drinking-water Quality - Chlorine Dioxide
WHO - World Health Organization
- Drinking Water Inspectorate guidance
UK Government - Drinking Water Inspectorate
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