Gravity Cartridges
The Coldstream FTO Plus is a replacement filter cartridge for gravity water systems. It is the standard cartridge for our ARMOUR Stainless Steel Gravity System, a drop-in replacement for discontinued ProOne® gravity filters, and compatible with Berkey® stainless steel housings.
Which systems does the Coldstream FTO Plus fit?
The Coldstream FTO Plus fits the following gravity water systems:
- ARMOUR Gravity System — this is the original cartridge for the ARMOUR, our BPA-free stainless steel system
- ProOne® Big, Big+, and Traveler+ — direct drop-in replacement, made in the same UK factory that manufactured the original ProOneG2.0 gravity elements. It does not fit ProOne pitcher filters or the ProOne Scout
- Berkey® stainless steel housings — mounts in place of Black Berkey® elements with no modifications
If your gravity system uses standard single-mount cartridges, the Coldstream FTO Plus will likely fit. Contact us with your system model if you're unsure.
What does it reduce?
The Coldstream FTO Plus is independently tested and certified to NSF/ANSI Standards 42, 53, and P231. It reduces fluoride, chlorine, lead, heavy metals, VOCs, PFAs and microbiological contaminants including bacteria and cysts. Unlike most Berkey replacement elements, fluoride reduction is built into the cartridge — no separate fluoride add-on filter is required.
Coldstream FTO Fluoride Gravity Filter Cartridge FAQ
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The FTO Plus is a standard 8-inch gravity cartridge that fits:
- Berkey systems
- British Berkefeld systems
- ProOne Big, Big+, and Traveler+
- The ARMOUR Stainless Steel Gravity Filter
- Most other stainless steel gravity housings
It is not compatible with ProOne pitcher or Scout models, which use a different cartridge format.
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The Coldstream FTO Plus is made in the same UK factory that produced the original ProOne G2.0 elements, and it drops into the same housings. If your ProOne gravity elements are due for replacement, the FTO Plus takes their place with no adapters or modifications — the same ceramic-shell, all-in-one design you're used to.
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Two stages work together in one cartridge. The ceramic outer shell filters out bacteria, cysts, and sediment, and the granular activated-carbon core reduces fluoride, chlorine, lead and other heavy metals, PFAS, and microplastics. There is no separate fluoride add-on element to buy or hang in the lower tank.
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Yes. The FTO Plus is independently tested and certified to NSF/ANSI 42 (aesthetic effects), NSF/ANSI 53 (health effects), and NSF/ANSI P231 (microbiological purification). An accredited third party verified the performance claims — they don't rest on the manufacturer's own testing.
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Match the number of elements your system currently runs — most households run two. More cartridges filter more water per hour and extend the replacement interval: one cartridge lasts 6 months, two last 12 months, and four last 24 months.
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No priming. Fit the cartridge, fill the upper chamber, and discard the first two tanks of water as a rinse before drinking. There's no soaking or faucet-pressure priming step of the kind some gravity elements require.
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Every 6 months for a single-cartridge setup, 12 months for two, or 24 months for four. Slowing flow is a visible cue the ceramic shell is loading with sediment, but the carbon core's fluoride capacity depletes on schedule even when flow still seems fine — so replace by the calendar, not just by flow.
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Yes. Subscribe & Save delivers replacement cartridges on your schedule — every 6, 12, or 24 months to match your setup — so a due date never catches you without a fresh filter on hand. Subscribers also save 5% on every delivery, and you can pause or cancel anytime.
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In the United Kingdom, at the same factory that manufactured the original ProOne G2.0 gravity elements. The ceramic-shell construction is also about 95% plastic-free.