Osmio PROMAX-III-XL Ultimate · High-capacity three-stage filtration
Advanced whole-house filtration in full-size 20-inch housings
The Osmio PROMAX-III-XL combines specialist PFAS and fluoride media, catalytic chloramine carbon and NanoCeram® filtration. Its three 4.5 × 20-inch stages provide greater media capacity than the standard PROMAX-III while treating the incoming mains supply before it travels around the home.
Point-of-entry treatment
Treat the supply before it reaches taps, showers and appliances
Installed on the incoming cold main, the PROMAX-III-XL combines chemical, disinfectant and fine-particle reduction in one high-capacity system. It is intended for larger homes and installations where longer 20-inch cartridges are preferable to compact 10-inch housings.
- Three specialist 4.5 × 20-inch filter cartridges
- PFAS, fluoride, chlorine and chloramine reduction
- 0.2-micron final NanoCeram® filtration
- 1-inch female BSP parallel brass connections
- No electrical supply or regeneration cycle required
Specialist stages Complementary treatment media
XL cartridges Greater media volume and capacity
NanoCeram® final stage Fine particle filtration
15 L/min optimal flow Published F-Guard guidance
The correct PROMAX-III-XL sequence
Three distinct stages with no Active Ceramics or KDF/GAC cartridge
The PROMAX-III-XL must not be confused with the PRO-III-XL. Water passes through F-Guard first, catalytic carbon second and NanoCeram® third.
F-Guard PFAS & Fluoride Filter · 2 Micron
Advanced adsorption media designed to reduce PFAS, PFOA, PFOS, fluoride, chlorine, chloramine, lead, other heavy metals, VOCs, THMs, pesticides, herbicides, pharmaceuticals and microplastics. Published PFAS and fluoride capacity is 21,000 litres, with an optimal flow rate of 15 L/min. A separate lead, mercury, chloramine and chlorine capacity of 78,358 litres is stated at 11.4 L/min.
Catalytic Chloramine Carbon Block · 0.5 Micron
High-performance coconut-shell activated carbon for chlorine and chloramine reduction, helping improve taste and odour while reducing a range of organic chemical compounds. Published chloramine capacity is 7,000 US gallons, approximately 26,500 litres, at 15.2 L/min. Projected chlorine taste and odour capacity is listed above 760,000 litres at the same test flow.
NanoCeram® Pleated Filter · 0.2 Micron
Electropositive nanofibre media designed to capture fine sediment, turbidity, cysts, bacteria and submicron particles while retaining useful flow through a large pleated surface area.
Test conditions matter: Percentage claims are reported in the F-Guard datasheet against its stated test standards. Real-world performance and cartridge life depend on flow, water chemistry, contaminant concentration and total usage.
Choose the correct Osmio system
PROMAX-III-XL and PRO-III-XL are different products
Similar names conceal different cartridge technologies. The PROMAX model focuses on PFAS, fluoride, chloramine and 0.2-micron final filtration; the PRO-III-XL uses a different Active Ceramics, carbon and KDF/GAC set.
PROMAX-III-XL
F-Guard, catalytic chloramine carbon and NanoCeram®.
20-inch cartridge format
Higher media volume than the standard 10-inch PROMAX-III.
Not a water softener
It does not remove dissolved hardness minerals or produce soft water.
Plan before ordering
High-capacity filtration still requires sufficient pressure and space
The three large housings become a substantial, heavy part of the main plumbing. Wall strength, standing pressure, peak demand, pipe size, bypass design and cartridge servicing clearance must all be confirmed.
Confirm at least 3 bar
Osmio recommends a minimum standing pressure of 3 bar for optimal performance and reduced impact on household flow.
Size around the limiting stage
F-Guard has a published optimal flow of 15 L/min. The 70 L/min figure applies only to an empty individual housing, not the complete system.
Install a bypass
A three-valve bypass allows the system to be isolated for filter changes without permanently interrupting the property supply.
Allow servicing clearance
Each housing is approximately 617 mm high. Leave at least 2 inches beneath every bowl and space to handle a full, water-filled housing.
Three antibacterial XL housings
Built around full-size 4.5 × 20-inch cartridges
The system uses three reinforced Osmio housings with brass 1-inch BSP connections. Silver-based antimicrobial protection is incorporated into the housing plastic to protect the product material.
- Reinforced polypropylene heads and PET bowls
- EPDM O-rings and pressure-release valve seals
- Maximum housing working pressure: 6 bar
- Complete-system working temperature: 4–38°C
- Individual housing size: 617 × 190 × 185 mm
Important: Antimicrobial housing construction protects the housing material. It does not mean the plastic itself disinfects the incoming water.
Maintenance and commissioning
Replace on condition and do not exceed the annual service interval
Osmio recommends replacing the three cartridges approximately every 12 months, with earlier replacement where usage, source-water quality or declining flow requires it. After replacement, fill slowly, flush until clear and inspect every joint and bowl for leaks.
Technical information
Osmio PROMAX-III-XL Ultimate specification
Installation information
Read the installation guide before arranging the plumbing
The guide covers pressure checks, bypass planning, cartridge order, mounting, O-ring preparation, commissioning and filter replacement.
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Helpful answers
Frequently asked questions
What is the difference between PROMAX-III-XL and PRO-III-XL?
The PROMAX-III-XL contains F-Guard, catalytic chloramine carbon and NanoCeram®. The PRO-III-XL uses Active Ceramics, a carbon block and a KDF/GAC filter. They are not interchangeable product descriptions.
How does the XL model differ from the standard PROMAX-III?
Both use the same three treatment types, but the XL uses 4.5 × 20-inch cartridges instead of 4.5 × 10-inch cartridges. The XL therefore has a larger footprint and greater media volume.
Does the PROMAX-III-XL reduce PFAS and fluoride?
Yes. The first-stage F-Guard filter is specifically designed to reduce PFAS compounds, including PFOA and PFOS, together with fluoride and a wider range of chemical contaminants.
Does the system remove bacteria?
The NanoCeram® stage is designed to reduce bacteria, cysts and fine particles. The system must still be used with microbiologically safe, adequately disinfected water and is not a substitute for correctly specified UV treatment on an unsafe private supply.
Will the system deliver 70 litres per minute?
Not necessarily. Seventy litres per minute is the maximum rating of an empty individual 20-inch housing. The F-Guard datasheet gives an optimal flow of 15 L/min. Actual output also depends on incoming pressure, pipework and the condition of all three cartridges.
How often should the cartridges be replaced?
Osmio recommends replacement approximately every 12 months. Replace sooner if source-water quality, heavy consumption or falling pressure and flow indicate that a cartridge is becoming exhausted or blocked.
Does the PROMAX-III-XL soften hard water?
No. It does not remove dissolved calcium and magnesium. A separate ion-exchange water softener is required when hardness and limescale removal are the main objectives.
Premium product support
Need to confirm pressure, peak flow or installation space?
Send us the incoming pipe size, measured standing pressure and flow, property size and available wall dimensions. We will help assess whether the PROMAX-III-XL is appropriately sized before ordering.