Both ceramic gravity filters and reverse osmosis systems are designed to improve the quality of your drinking water. But there is one fundamental difference between them:
Reverse osmosis removes almost everything from the water — including its naturally occurring minerals. A ceramic gravity filter reduces unwanted contaminants while allowing those natural minerals to remain.
Reverse osmosis: removing almost everything
Reverse osmosis, or RO, uses pressure to push water through an extremely fine membrane.
It is a powerful filtration method because it removes an extremely broad range of substances from water. But it doesn't distinguish between unwanted contaminants and naturally occurring dissolved minerals.
Along with contaminants, RO removes minerals such as calcium and magnesium that are naturally present in drinking water.
This leaves highly purified, largely demineralised water. Some RO systems therefore include an additional remineralisation stage to add minerals back into the water afterwards.
Ceramic gravity filtration: a more selective approach
A ceramic gravity filter works differently.
Water slowly passes through a ceramic filter element using gravity alone. The filtration media target unwanted substances, while naturally occurring dissolved minerals such as calcium and magnesium are small enough to pass through and remain in the water.
With Claii, this means reducing contaminants such as:
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Microplastics
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Bacteria and cysts
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Chlorine
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Lead and other heavy metals
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PFAS such as PFOA and PFOS
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Sediment and fine particles
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Many organic chemicals
Without stripping the water of its naturally occurring minerals.
A simpler system to live with
There is also a practical difference between the two.
Reverse osmosis systems are typically installed under the kitchen sink and often require a separate drinking-water tap. That can mean plumbing work and drilling into your countertop or sink — something you may not want to do, especially when renting.
A ceramic gravity filter simply sits on your countertop. No permanent changes to your kitchen are needed, and you can take it with you when you move.
There is something refreshingly simple about it.
No electricity.
No plumbing.
No wastewater.
No drilling or complicated installation.
Just water, gravity and a carefully designed filter.
So, which is better?
That depends on your water and what you want to achieve.
Reverse osmosis can be a good choice when you specifically need to remove substances that ceramic filtration isn't designed to target, such as high levels of dissolved salts or nitrates.
But for everyday drinking water, you may not necessarily want to remove everything.
At Claii, we chose ceramic gravity filtration because we wanted a more selective approach: reducing what doesn't belong in your water, while keeping the minerals that naturally do.
Effective filtration, without completely stripping the water of its natural mineral content — in a system designed to simply become part of your home.