Oxygen pool treatment uses active oxygen, primarily hydrogen peroxide (H₂O₂) combined with polyhexamethylene biguanide (PHMB) as sanitiser, as a complete chlorine-free pool water management system, with hydrogen peroxide acting as oxidiser breaking down body oils, sunscreen, organic contaminants and algae while PHMB provides ongoing bacterial disinfection at 30-50 ppm concentration maintained every 10-14 days.
The system eliminates chlorine entirely without chlorine tablets, no chlorine shock, no chlorine smell, and no chloramines, producing soft odourless water gentle on skin and eyes by decomposing to water and oxygen with no chemical residue. A third component, polyquat algaecide, added weekly provides supplemental algae prevention since neither hydrogen peroxide nor PHMB alone reliably prevents all algae types.
This guide covers how the complete oxygen treatment system works (PHMB sanitiser + H₂O₂ oxidiser + algaecide), the distinct role of each component, PHMB chemistry and application schedule, hydrogen peroxide dosing (35% concentration, maintenance vs shock doses), potassium monopersulfate (MPS) as alternative oxidiser, chemical incompatibilities (PHMB incompatible with chlorine, ozone, ionisers), filter maintenance requirements (PHMB forms particles loading filter faster), system costs, water quality advantages, limitations (white water mould risk, no residual sanitiser gap protection), conversion from chlorine to oxygen treatment, and natural pool alternative eliminating all chemical treatment.
Key Takeaways
- Three components required: PHMB sanitiser + hydrogen peroxide oxidiser + polyquat algaecide
- PHMB: 30-50 ppm maintained – applied every 10-14 days, the only standalone non-chlorine sanitiser
- Hydrogen peroxide: oxidiser not sanitiser – breaks down organics, does not reliably kill all bacteria alone
- MPS alternative: Potassium monopersulfate used instead of H₂O₂ for shock oxidation in some systems
- PHMB incompatible with chlorine – never mix, serious chemical reaction
- Filter cleans more frequently – PHMB forms insoluble particles loading filter faster than chlorine systems
- White water mould risk higher – oxygen treatment pools more prone to Saprolegnia than chlorine pools
- Natural pools: zero chemicals – biological filtration replaces entire oxygen treatment system
There's a System That Goes All the Way
The Three-Component Oxygen Treatment System
Component 1: PHMB Sanitiser
What PHMB is: Polyhexamethylene biguanide is an organic polymeric compound classified as EPA-registered sanitiser. The only non-chlorine, non-halogen sanitiser approved for standalone use in residential swimming pools.
How it works: PHMB disrupts bacterial cell membranes by binding to bacterial cell wall components, causing cell contents to leak and bacteria to die. Unlike chlorine (oxidative mechanism), PHMB kills bacteria through physical disruption of membrane integrity.
Application: Liquid product applied by pouring around the pool perimeter with the pump running. Initial dose establishes 30-50 ppm concentration. Maintenance dose of 10-15 ml per 1,000 litres applied every 10-14 days compensates for degradation and splash-out.
Testing: Test PHMB concentration using PHMB-specific test strips (standard chlorine test kits do not measure PHMB). Maintain 30-50 ppm. Below 30 ppm, the disinfection is insufficient and above 50 ppm, it is unnecessary excess without additional benefit.
Incompatibilities: PHMB is incompatible with chlorine, bromine, ozone, ionisers, TSP, and certain other pool chemicals. Adding chlorine to a PHMB pool (or vice versa) causes a serious chemical reaction of cloudy white precipitation, and potential swimmer safety hazard. Must completely flush the system (partial drain, full drain, or extended water exchange) before switching between PHMB and chlorine systems.
Brand names: Baquacil, Soft Swim, Aqua Silk, or Revacil are all polyhexamethylene biguanide formulations.
Component 2: Hydrogen Peroxide (H₂O₂) Oxidiser
Role: Oxidiser, not primary sanitiser. Hydrogen peroxide breaks down organic contaminants such as body oils, sunscreen, sweat, cosmetics, or dead skin cells that accumulate in pool water and consume PHMB. PHMB does not oxidise these organics efficiently on its own.
Concentration: Pool-grade hydrogen peroxide sold at 27-35% concentration. Standard household H₂O₂ (3%) is insufficient – it requires impractical volumes for pool treatment. Use pool-specific formulation.
Decomposition: H₂O₂ breaks down into water (H₂O) and oxygen gas (O₂) without any chemical residue. This is the “oxygen” in oxygen pool treatment. Oxidised water releases dissolved oxygen as a reaction byproduct.
Application schedule: Applied every 3-4 weeks for routine oxidation maintenance, and additionally after heavy use or visible organic loading (cloudy water, waterline film, strong odour).
Shock dose (new pool setup or high organic load): 2.7 litres per 40,000 litres pool volume of 30% H₂O₂ achieves 80-100 ppm shock concentration.
Maintenance dose: 0.5-0.75 litres per 40,000 litres every 3-4 weeks.
Do not use with chlorine: Hydrogen peroxide neutralises chlorine. Adding H₂O₂ to a chlorinated pool destroys the chlorine residual immediately. This is why PHMB and H₂O₂ function only as a complete system without chlorine.
Component 3: Polyquat Algaecide
Role: Supplemental algae prevention. Neither PHMB nor hydrogen peroxide reliably prevents all algae types (particularly mustard algae and black algae) when used alone. Weekly polyquat algaecide addition fills this prevention gap.
Polyquat: Polyquaternary ammonium compound (polyquat 60% formulation) is compatible with the PHMB system unlike copper-based algaecides which react with PHMB.
Application: 60-120 ml per 40,000 litres weekly during pool season.
Compatibility check: Always verify algaecide label states compatibility with biguanide/PHMB systems before adding. Copper algaecides and some other formulations are incompatible.
Potassium Monopersulfate (MPS) as Alternative Oxidiser
Some oxygen treatment systems substitute or supplement hydrogen peroxide with potassium monopersulfate (MPS) – a granular non-chlorine oxidiser also called non-chlorine shock.
Form: White granular powder or tablet. Dissolves rapidly in water.
How it works: Releases active oxygen (peroxide chemistry) on dissolution in pool water, oxidising organic contaminants.
Advantages over H₂O₂: Granular form easier to measure and store than liquid peroxide. Longer shelf life. No special containers or child-proof storage required.
Limitations: Higher cost per oxidising dose than liquid hydrogen peroxide. Some pool professionals find liquid H₂O₂ more effective for heavy organic loads.
Application: 150-200 grams per 40,000 litres for maintenance oxidation every 2-3 weeks. Pre-dissolve in a bucket of pool water before adding (prevents granule contact with pool surfaces causing bleaching).
Compatibility: MPS compatible with PHMB and polyquat components of the oxygen treatment system. Incompatible with chlorine (neutralises free chlorine), it has the same restriction as hydrogen peroxide.
Setting Up an Oxygen Treatment System
New Pool Setup
- Fill pool with fresh water, balance chemistry (pH 7.2-7.6, alkalinity 80-120 ppm, calcium hardness 200-400 ppm)
- Add initial PHMB dose to establish 30-50 ppm concentration (consult product label for volume-specific dosage)
- Run pump minimum 4 hours after PHMB addition
- Test PHMB level using biguanide test strips to confirm target range
- Add initial hydrogen peroxide shock dose (2.7 litres 30% H₂O₂ per 40,000 litres)
- Run pump 24 hours
- Add polyquat algaecide initial dose per product instructions
- Do not swim until PHMB concentration confirmed 30-50 ppm and water clear
Converting from Chlorine Pool
Important: Must remove all chlorine from water before introducing PHMB.
- Stop all chlorine additions
- Allow free chlorine to deplete naturally below 0.5 ppm (test daily – typically 5-10 days with pump running, sunlight exposure)
- Do not add sodium thiosulphate dechlorinator – residue may interfere with PHMB
- Once chlorine confirmed below 0.5 ppm, drain 30-50% of pool water and refill (removes residual chlorine more effectively)
- Clean filter thoroughly (cartridge soak in cleaning solution, sand filter cleaner, DE grid scrub – removes chlorine-treated debris)
- Replace filter cartridge if possible – fresh media prevents chlorine residue interference
- Begin PHMB setup procedure as above
Timeline: 2-3 weeks from last chlorine addition to first PHMB addition.
Maintenance Schedule
Weekly
Apply polyquat algaecide (60-120 ml per 40,000 litres). Test pH and adjust if outside 7.2-7.6 range. Skim, brush, vacuum = identical to chlorine pool routine. Check the PHMB test strip (confirm 30+ ppm, add maintenance PHMB if below).
Filter cleaning: PHMB forms insoluble particles with some pool contaminants. These particles load filters faster than typical chlorine pools. Check filter pressure weekly. Clean when pressure rises 5-8 PSI above baseline (sooner than typical chlorine pool schedule).
Every 10-14 Days
Add PHMB maintenance dose (10-15 ml per 1,000 litres) to maintain 30-50 ppm concentration.
Every 3-4 Weeks
Add hydrogen peroxide oxidation treatment. Pour H₂O₂ around the pool perimeter with the pump running. Do not swim for 15-30 minutes after addition.
Test water for cloudiness (indicates organic loading requiring additional H₂O₂) or algae development (indicates algaecide gap requiring additional polyquat).
Monthly
Deep clean filter completely (cartridge soak or sand filter cleaner treatment). PHMB systems require more frequent filter servicing. Insoluble PHMB-contaminant particles accumulate in filter media faster than chlorinated pool debris.
Water Quality Advantages
No Chlorine Smell
PHMB and H₂O₂ produce no chloramines. Chloramines form when chlorine reacts with nitrogen compounds from swimmer waste and is responsible for “swimming pool smell” and eye/skin irritation. Oxygen-treated pool water is odorless and clear.
Skin and Eye Comfort
Free chlorine at 1-3 ppm causes measurable skin dryness, eye irritation, and swimsuit colour fade over time. PHMB-treated water is noticeably softer and gentler. Particularly beneficial for children swimming frequently, people with eczema or psoriasis, and contact lens wearers.
Swimmer Safety
No chlorine gas inhalation risk during chemical addition (indoor pools particularly). No chlorine storage, handling, or measuring hazards.
Environmental
H₂O₂ decomposes entirely to water and oxygen without chemical discharge to drainage or environment. PHMB degrades slowly in water but does not produce harmful environmental byproducts at pool concentrations.
Limitations and Challenges
White Water Mould Higher Risk
Oxygen treatment pools experience significantly higher incidence of white water mould (Saprolegnia spp.) than chlorine pools. PHMB is effective against bacteria but does not prevent water mould biofilm establishment in the same way chlorine does.
Management: More frequent monitoring, aggressive algaecide additions, thorough filter cleaning if mould detected. Treatment of water mould in the PHMB system requires biguanide-specific products (cannot use chlorine shock as it is incompatible).
Filter Maintenance Intensity
PHMB forms insoluble particles with pool contaminants. These particles accumulate in filter media faster than chlorinated pool debris requiring filter cleaning every 1-2 weeks in active season versus every 3-4 weeks for chlorine pool.
System Incompatibility
Strict chemical incompatibilities require complete water exchange if switching sanitiser systems. Accidental chlorine addition (e.g., maintenance worker unfamiliar with the system) causes immediate serious water quality problems.
Cost
Annual costs are around €400-600 (PHMB maintenance doses, H₂O₂, polyquat algaecide), which is significantly higher than chlorine (€200-400) due to more expensive chemical components, particularly PHMB.
Limited Availability
PHMB products are sold through specialist pool supply shops. They’re not universally available at supermarkets or hardware stores. Requires planning and access to informed suppliers.
AOP Systems: Hydrogen Peroxide + UV
Advanced Oxidation Process (AOP) systems combine UV light with hydrogen peroxide at injection point where UV radiation splits H₂O₂ molecules create hydroxyl radicals (•OH), among the most powerful oxidisers known.
Performance: Hydroxyl radicals destroy bacteria, viruses, and organic compounds faster and more completely than H₂O₂ or UV alone.
Application: Commercial pools, institutional facilities, high-end residential pools prioritising absolute minimal chemical use.
Cost: €3,000-8,000 installation. Ongoing electricity and UV bulb replacement.
Requirement: Still requires small residual sanitiser (0.5 ppm hydrogen peroxide maintained in water) for protection between circulation cycles.
Natural Pool Alternative: Zero Chemicals
Oxygen pool treatment represents a significant reduction in chemical harshness compared to chlorine without the chlorine smell, no chloramines, and gentler water. However, it still requires ongoing chemical management: PHMB dosing every 10-14 days, H₂O₂ oxidation every 3-4 weeks, weekly algaecide, frequent filter cleaning, strict chemical compatibility management, and annual costs of €400-600.
Natural swimming pools eliminate the entire chemical treatment regime through biological filtration, providing genuinely chemical-free water maintenance.
How biological filtration replaces PHMB: Beneficial bacteria in regeneration zone gravel substrate and plant roots perform the same bacterial disinfection role as PHMB. Through competitive exclusion and biological antagonism rather than chemical disruption. Dense established beneficial bacterial populations outcompete pathogenic bacteria for resources, preventing dangerous bacterial dominance without chemical sanitiser.
How plants replace H₂O₂: Aquatic plants (Typha, Phragmites, Juncus, Iris) absorb dissolved organic nitrogen, phosphorus, and other compounds through root systems continuously. They are the same organic compounds that H₂O₂ oxidises in oxygen treatment pools. Plants remove these substances biologically before they accumulate to problematic levels.
No white water mould risk: The elevated white water mould incidence associated with PHMB systems is absent in natural pools. Beneficial ecological communities in regeneration zones competitively exclude Saprolegnia – the competitive exclusion mechanism that is absent in chemically simplified PHMB-treated water.
Operating costs: €100-300 annually (pump electricity only) versus €400-600 for oxygen treatment system. Seasonal plant maintenance (trimming dead foliage, dividing overcrowded plants) replaces chemical dosing schedule.
Portugal climate advantage: Mediterranean temperatures maintain year-round biological activity. Plants and bacteria are active even in winter months in coastal regions so biological filtration should be continuous, with no seasonal restarts or chemical re-establishment.
Oásis Biosistema designs natural swimming pools using planted regeneration zones where aquatic plants and beneficial bacteria eliminate the need for PHMB, hydrogen peroxide, algaecide, and all chemical treatments, providing genuinely chemical-free pool water maintenance at lower annual cost than oxygen treatment systems through biological filtration in Portuguese landscape installations.
Conclusion
Oxygen pool treatment requires three components working together: PHMB sanitiser (polyhexamethylene biguanide maintained at 30-50 ppm every 10-14 days), hydrogen peroxide oxidiser (27-35% concentration applied every 3-4 weeks breaking down organics to water and oxygen), and polyquat algaecide (weekly, compatible formulation only), producing chlorine-free, odourless water but requiring strict incompatibility management (never mix with chlorine, ozone, or copper algaecides), more frequent filter cleaning due to PHMB particle formation, vigilance against elevated white water mould risk, and annual chemical costs of €400-600.
Natural swimming pools designed by Oásis Biosistema eliminate the entire chemical treatment regime: PHMB, hydrogen peroxide, algaecide, and all dosing schedules, through biological filtration in planted regeneration zones where beneficial bacteria and aquatic plants maintain water quality continuously at €100-300 annually for pump electricity in chemical-free Portuguese pool installations.
FAQ
What are the benefits of an oxygen pool?
An oxygen-based pool system uses alternatives like hydrogen peroxide or advanced oxidation instead of heavy chlorine use. Benefits can include softer-feeling water, reduced chemical smell, less skin and eye irritation, and a more natural swimming experience when properly maintained.
What is an oxygen pool?
An “oxygen pool” usually refers to a pool sanitized with active oxygen systems such as hydrogen peroxide or mineral/UV-based setups. It reduces reliance on traditional chlorine, but still requires regular balancing and sometimes a small backup sanitizer.
Are ozone pools better than chlorine?
Ozone water treatment systems can reduce chlorine usage and improve water clarity, but they are not a full replacement. Chlorine provides a lasting residual sanitizer, while ozone works instantly but does not stay active in the water for long periods.
What are the disadvantages of ozone pools?
Disadvantages of ozone water treatment include higher installation cost, lack of long-lasting protection, and the need for a backup sanitizer like chlorine. Systems also require proper maintenance and may not fully eliminate all contaminants without supplemental chemicals.
