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4.5 x 10 Inch Carbon Block Filter Cartridge

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A compact 4.5" × 10" activated carbon block replacement cartridge that reduces chlorine, improves taste and odour, and filters fine sediment for cleaner, fresher mains water.

Reduces up to 99% of chlorine while improving the taste and smell of mains water.
Fits the Moby and most 4.5" x 10" Big Blue® filter housings for straightforward replacement.
Carbon block filtration reduces chlorine, taste, odour and fine sediment more consistently than GAC cartridges.
Optional siliphos hard water insert helps reduce limescale formation in medium hard water areas.
NSF/ANSI Standard 42 certified with a service life of up to 12 months, depending on water quality and usage.

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SKU: WWQ-WCBFF975

A compact 4.5" × 10" activated carbon block replacement cartridge that reduces chlorine, improves taste and odour, and filters fine sediment for cleaner, fresher mains water.

Reduces up to 99% of chlorine while improving the taste and smell of mains water.
Fits the Moby and most 4.5" x 10" Big Blue® filter housings for straightforward replacement.
Carbon block filtration reduces chlorine, taste, odour and fine sediment more consistently than GAC cartridges.
Optional siliphos hard water insert helps reduce limescale formation in medium hard water areas.
NSF/ANSI Standard 42 certified with a service life of up to 12 months, depending on water quality and usage.

Compatibility

This 4.5 x 10 activated carbon block replacement cartridge is designed for our Moby mains water filter and is compatible with most standard 10 inch Big Blue style filter housings that accept 4.5 x 10 inch cartridges.

It's compact size makes it ideal for smaller whole house and point-of-entry water filtration systems, helping to reduce chlorine, improve taste and odour, and filter fine sediment before the water reaches your cold water taps.

Not sure if this is the right replacement cartridge for your filter housing? Contact us and we'll be happy to help you identify the correct cartridge before you order.

What it reduces and what it doesn't

This 4.5'' x 10'' activated carbon block replacement cartridge is designed for use in 10'' Big Blue style filter housings. Made from 100% coconut shell activated carbon, it helps reduce chlorine, improve the taste and odour of mains water, and filter fine sediment before the water reaches your cold water taps.

If you're looking to reduce limescale, the cartridge can be supplied with an optional siliphos hard water insert. For fluoride, heavy metals or bacteria, you'll need a filter cartridge specifically designed for those contaminants.

Contaminant	Performance
Chlorine	Reduces - up to 99%
Taste	Improves
Odour	Improves
Sediment	Reduces
Limescale	No (optional hard water insert available)
Fluoride	No
Heavy Metals	No
Bacteria	No

Specifications - Watts WCBFF975

Product code	Watts WCBFF975
Size	4.5" x 10" (fits most standard 10" 'Big Blue' style filter housings)
Filter type	100% coconut shell activated carbon block, with a protective media wrap to help reduce carbon fines
Micron rating	5 micron
Recommended flow rate	4 gpm (approximately 15 lpm)
Maximum operating pressure	125 PSIG (approximately 8.6 bar)
Operating temperature	10ºC - 52ºC (50ºF - 125ºF)
Chlorine reduction*	Up to 99% reduction; > 37,850 litres / 10,000 US gallons @ 2 gpm
Approvals & certifications	Tested and certified to NSF/ANSI Standard 42 (materials); FDA grade components and materials
Optional	Siliphos hard water insert to help reduce limescale formation

*Performance depends on water chemistry,, flow rate, system design and application. Claims apply when installed in a complete water filtration system.

Specifications - Matrikx CTO

On some occasions a Matrikx CTO cartridge may be sent instead. This does the same job as the Watts WCBFF975 - they're just different brands.

Product code	Matrikx CTO 32-450-10
Size	4.5" x 10" (fits most standard 10" 'Big Blue' style filter housings)
Filter type	100% coconut shell activated carbon
Micron rating	5 micron nominal filtration
Chlorine reduction capacity	136,500 litres / 36,000 US gallons @ 3.0 gpm
Approvals & certifications	Certified to NSF/WQA (materials only). Manufactured in an ISO 9001 and 14001 certified facility. Certified for sustainability by WQA S-803

*Dependent on local water chemistry, flow rates, system design and application. Performance claims apply to a fully installed system with filter, housing, and connection to pressurised water.

How often to change and signs it needs changing

We recommend replacing your carbon block cartridge every 12 months to maintain effective chlorine, taste, odour and sediment reduction.

Depending on stock availability, you may receive either the Watts WCBFF975 or the Matrikx CTO replacement cartridge. The rated filtration capacity is over 37,850 litres (10,000 US gallons) for the Watts cartridge or 136,500 litres (36,000 US gallons) for the Matrikx cartridge, although actual service life will vary depending on your water quality and usage.

Typical signs that it's time to replace the cartridge include:

Reduced flow rate
The taste or smell of chlorine beginning to return
The cartridge reaching its recommended service liffe

To make maintenance easier, we'll send you a remindeer email every six months so you know when it's time to check your cartridge.

How to replace

Replacing the cartridge is straightforward and only takes a few minutes.

Turn off the water supply and open a downstream cold tap to relieve the pressure.
Using the housing spanner, unscrew the filter housing bowl. Have a container or towels ready to catch any water remaining in the housing.
Remove the old cartridge, rinse the housing bowl and inspect the O-ring. Clean, reseat or replace the O-ring if necessary.
Fit the new cartridge and screw the housing bowl back onto the cap by hand. Do not overtighten.
Turn the water supply back on, check for leaks, then flush the new cartridge for 1–2 minutes to remove any harmless carbon fines before use.

FAQs

Will this cartridge fit my water filter?

This cartridge is designed for our Moby mains water filter and is compatible with most standard 4.5" × 10" Big Blue style filter housings. If you're unsure whether it's the correct replacement for your system, contact us and we'll be happy to help.

What's the difference between a carbon block and a GAC cartridge?

A carbon block cartridge is made from compressed activated carbon, providing more consistent filtration than granulated activated carbon (GAC). It helps reduce channelling, offers effective chlorine, taste and odour reduction, and also filters fine sediment down to 5 microns.

Can I use this cartridge if I live in a hard water area?

Yes. You can choose the optional Siliphos hard water insert, which helps reduce limescale forming in pipework and appliances. It does not soften the water or remove dissolved hardness minerals.

How often should I replace the cartridge?

For the best filtration performance, replace the cartridge every 12 months. You may also need to replace it sooner if you notice reduced water flow or the taste or smell of chlorine returning.

Why does the cartridge need flushing after installation?

New carbon block cartridges can release a small amount of harmless carbon dust, known as carbon fines, during first use. Flushing the cartridge for 1–2 minutes removes these fines and prepares the filter for normal use.

Does this cartridge remove chloramine as well as chlorine?

Yes. The activated carbon block is designed to reduce both chlorine and chloramine, improving the taste and odour of treated mains water. The level of reduction will depend on factors such as your local water chemistry, water usage and flow rate.