• High performance carbon block filtration - reduces chlorine, unpleasant tastes, odours and sediment to deliver cleaner, fresher mains water throughout your home.
• 20" 'Big Blue' replacement cartridge - the replacement cartridge for our Doby whole house water filter, and a fit for other 20" 'Big Blue' style water filter housings.
• Whole-house capacity - a high-capacity 5 micron carbon block rated to over 26,000 gallons, ideal for a small house with up to four occupants.
• Optional hard water protection - add the hard water insert and siliphos crystals are included with your cartridge to help reduce scale.
• Long lasting, certified performance - up to 12 months of filtration, certified to NSF/ANSI Standard 42 and ISO 9001, and independently laboratory tested.

Compatibility | What it reduces | Specs | How often to change | How to replace | FAQs | Reviews

Compatibility

This 4.5" x 20" carbon block water filter cartridge is the replacement cartridge for our Doby whole house water filter, and it also fits other 20" 'Big Blue' style water filter housings. The Doby is a mains water filter ideally suited to a small house with up to four occupants, improving the taste and smell of your water while reducing chlorine and sediment at every tap.

Unsure if this is the correct replacement cartridge for your system? Contact us and we'll help.

What it reduces and what it doesn't

A high-capacity CTO (chlorine, taste and odour) coconut shell carbon block cartridge that reduces chlorine, taste, odour and sediment for cleaner, better-tasting water across the whole house. If you're on mains water there will be chlorine or chloramine present.

This carbon block cartridge does not treat limescale or reduce fluoride on its own, although you can add the optional hard water insert (siliphos crystals) to help reduce scale.

Specifications

How often to change and signs it needs changing

We recommend changing your cartridge every 12 months, or after approximately 98,420 litres / 26,000 US gallons, whichever comes first. Signs it's due include reduced water flow and a returning taste or smell of chlorine. We'll also send you an email every 6 months to remind you to check your filter's performance.

How to replace

To change your cartridge, follow these steps:

1. Turn off the water supply and open a downstream tap to release the pressure.
2. Using the housing spanner, unscrew the housing bowl from the cap. The 20" bowl will be full of water and heavy, so take care and have a container or towels ready.
3. Remove the old cartridge, rinse out the bowl, and check the O-ring is in good condition (reseat or replace as needed).
4. Insert the new cartridge, then screw the bowl back onto the cap, hand-tight - do not over-tighten.
5. Turn the water supply back on, check for leaks, then flush the new cartridge for 1-2 minutes to remove any carbon fines before use.

FAQs

Which filter does this cartridge fit?

It's the replacement cartridge for our Doby whole house water filter, and it also fits other 20" 'Big Blue' style water filter housings. If you're not sure whether it suits your system, get in touch and we'll check for you.

What does this cartridge reduce?

It's a coconut shell CTO carbon block that reduces chlorine, taste, odour and sediment from your mains water. If you're on mains water there will be chlorine or chloramine present, and this cartridge improves the taste and smell across your whole house.

Can I use it to treat hard water?

Yes. Choose the hard water insert option when you order and siliphos crystals will be added to your cartridge before despatch, helping to reduce scale. Note that this reduces scale build-up rather than fully softening the water.

Why do I need to change the O-ring?

Over prolonged time under compression the O-ring's profile can flatten; the cross section should be round, and if it isn't it may not seal easily. Even without an obvious leak we recommend replacing the O-rings every two or three years as a precaution. As O-rings age and compress, the bowl has to be tightened more, which makes it harder to loosen next time you change the cartridge.

How often should I change this cartridge?

We recommend every 12 months, or after approximately 98,420 litres / 26,000 US gallons, whichever comes first. You may also notice the taste or smell of chlorine returning when it's due.

Reviews