Gravity Water Filter: How Does It Work?

Reading time: ~12 minutes

Search in the Netherlands for "zwaartekracht waterfilter" and what you mostly get is gleaming stainless steel urns: prices from 54.95 euros to 277.00 euros, brands such as British Berkefeld, AQUA Logic, Phoenix Gravity and Aqualine, and plenty of photos of filters on a worktop in a tiny house. What you rarely get is a level-headed answer to the question you are actually asking: does one of these filter my tap water better than what I have now, and what do I give up in return?

In this article we explain how gravity filtration works technically, what it demonstrably removes, where it falls short and which situations it genuinely suits best. At PureFilter we see that customers who arrive at this type of filter usually want one of two things: independence from electricity and water pressure, or simply better-tasting drinking water. Those are two different problems, and they call for a different device.

1. What is a gravity water filter?

The principle is centuries old and deliberately kept simple. Because no pump or connection is needed, a filter like this works just as well on a worktop as in a campervan, on a boat or in a holiday home without a reliable mains supply. That also explains why the Dutch search results for this term are full of prepper and emergency-kit shops: rampenrugzak.nl, noodzaken.nl and prepshop.nl all three sit in the top 10.

One important difference from a filter jug: a filter jug (think of Brita or ZeroWater) also runs on gravity, but uses a small cartridge with activated carbon and an ion exchanger and is meant for 1 to 3 litres at a time. A true gravity filter holds a larger volume, 5 to 14 litres is common, and uses heavier filter elements, often ceramic. If you want a sharper picture of the difference between jugs and systems, read our honest review of the Brita filter jug alongside this article.

The category is not large in the Netherlands, but it is steady: according to DataForSEO the search term "zwaartekracht waterfilter" attracts around 110 searches per month, with clear peaks in winter, when 210 to 260 searches per month were measured. That pattern fits emergency preparedness: people search when supply security or power cuts are in the news.

2. How does gravity filtration work, step by step?

The process has three steps, and each one determines how well and how quickly your filter works.

Step 1: filling

You pour water into the upper chamber. Most household models hold 4 to 8.5 litres there; larger models such as the 14-litre dispensers and the 12-litre British Berkefeld go further. The weight of that column of water is the only "engine" the system has: the fuller the upper chamber, the higher the pressure on the filter element and the faster the water runs through.

Step 2: filtering

The water descends through one to four filter candles. In ceramic elements, the type British Berkefeld and Doulton use, a porous outer layer holds back particles and micro-organisms; the core often contains activated carbon to bind chlorine, taste and organic compounds. Ultrafiltration models such as the AQUA Logic series contain a membrane of around 0.03 micron, roughly three thousand times thinner than a human hair.

Step 3: drawing off

The filtered water collects in the lower chamber and comes out through a small tap. Expect a flow rate of roughly 1 to 10 litres per hour, depending on the number of filter elements and how full the upper chamber is. For comparison: your ordinary kitchen tap delivers more water in a single minute than a gravity filter produces in an hour. If you want to understand how that compares with other filtration techniques, our explanation of how a water filter works sets the five common techniques side by side.

3. What does a gravity filter take out of your water, and what does it miss?

This is where marketing and measurability part ways. Gravity filters are strong at two things: microbiology and taste. A ceramic element with a pore size of 0.2 micron or smaller physically holds bacteria back, and that is exactly why this filter type is used worldwide where water sources are unreliable. The activated carbon in the core removes chlorine, chlorine taste and many organic compounds.

What often gets too little attention: in the Netherlands that microbiological gain is limited for tap water. According to the RIVM, drinking water quality meets the statutory standards in more than 99.9 per cent of all measurements, and Dutch tap water is supplied without chlorine. A bacteria filter therefore solves a problem you usually do not have at the tap, unless the water has been standing still for a long time. That last point is real enough: Legionella multiplies in standing water between 25 and 55 degrees, which is why Vitens advises flushing every tap for at least a minute after a holiday.

Where it often goes wrong: PFAS and dissolved substances

Gravity filters work on particle size and adsorption. Dissolved substances that are small and bind poorly to carbon slip through more easily. PFAS is the clearest example of this. For the Netherlands that is not a theoretical question: the RIVM advises a health-based guideline value of 4.4 nanograms of PFAS per litre, while the statutory limit sits at 100 nanograms per litre, and in drinking water made from river water that stricter guideline value is regularly exceeded. If you want to filter specifically for this, look at a system that has been demonstrably tested for it, as described on our page about the water filter for PFAS.

A second blind spot is limescale. A gravity filter does not meaningfully lower the hardness of your water. According to Vitens, average water hardness in the Netherlands sits at around 8 German degrees, rising to 12 degrees in parts of the country. If limescale is what you are aiming at, you will be disappointed; how that does work is set out in our article on filtering limescale out of tap water.

And minerals?

Most gravity filters simply let calcium and magnesium pass, which is fine in itself. They just do not add anything. Filters that do remove everything, such as reverse osmosis, also strip out the minerals that give your water its taste. That difference decides how your water ends up tasting; we worked it out in the article on minerals in drinking water.

4. The best-known gravity filters in the Netherlands

These are the brands that actually turned up in the Dutch search results and shopping listings in August 2026, with the prices shown there. Prices vary by shop and by the moment; always check them with the seller.

What stands out in that list: the price spread is enormous, from 54.95 euros to 277.00 euros for systems that on paper do the same thing. The difference lies in the filter element, how long it lasts and whether the material is 304 stainless steel or plastic. If you are looking specifically at the ceramic camp, the details are in our Doulton water filter review, because Doulton and British Berkefeld come from the same ceramic tradition.

A second observation: none of these brands advertises full NSF certification for both taste and health claims. That matters, because NSF International distinguishes between NSF 42 (taste, chlorine, odour), NSF 53 (health claims such as lead) and NSF 401 (emerging contaminants such as pharmaceutical residues). A filter tested only for taste may therefore not carry a health claim.

5. Advantages of a gravity filter

• Works without electricity and without pressure: all you need is water and a difference in height. During a power cut or a burst main, the system simply keeps working.
• Portable: you can put it on the worktop, in the campervan, on the boat or in a tiny house. No installation, no tools, no connection.
• Suitable for other water sources: rainwater, spring water or, in an emergency, surface water. That is why the search term "waterfilter voor slootwater", with 880 searches per month, sits so close to this category.
• Long element life: under normal use, ceramic candles often last a year or longer and can sometimes be cleaned.
• Visible and easy to understand: you can see how much you have filtered and there is no electronics inside to fail.

For anyone looking for an emergency supply, this type of filter is hard to beat. The same goes for time away from home: in our guide to the water filter for travelling the gravity version returns as the logical choice as soon as you are staying in one place with more than two people.

6. Points to watch and common mistakes

You keep refilling, every day

A household of four soon drinks and cooks with 6 to 8 litres a day. With a 4-litre upper chamber that means filling twice a day, plus waiting time. That is exactly the point where most families give up; it is the same reason filter jugs so often end up unused in the cupboard after a few months.

Standing water in the lower chamber

Filtered water no longer contains any disinfectant. If it sits in the lower chamber for days, bacteria can multiply again, certainly in a warm kitchen. Rule of thumb: empty the lower chamber at least every 24 to 48 hours and clean both chambers weekly.

Worktop space and height

An 8.5-litre stainless steel system is soon 50 centimetres tall and weighs over 10 kilos when full. It often does not quite fit under a wall cupboard, and you need to be able to put a glass underneath it. Measure this beforehand.

Claims without certification

Pay close attention to phrasing such as "removes up to 99 per cent". The question is always: 99 per cent of what, measured by whom, at which flow rate. Independent certification to NSF 42, 53, 61 or 372 says considerably more than a percentage in a product description. How to judge claims like these is set out in our analysis of the Consumentenbond water filter test.

7. Gravity filter or under-sink filter?

Both systems filter drinking water, but they solve a different problem. This table sets the practical differences side by side.

The honest conclusion: if your scenario is "the tap has stopped working", the gravity filter wins. If your scenario is "I want good, clean drinking water every day without any fuss", a system on your mains supply wins. We made the same trade-off in our overview of the best water filter under the sink.

8. What does a gravity filter cost per year?

The purchase price is only half the story. Filter elements are the recurring item: expect about 30.00 to 70.00 euros per element, and with systems that take two or four candles that adds up. Under normal household use you replace them once a year, sometimes more often if your water is cloudy or if you run a lot of litres through it.

Set that against the source itself. In 2026 tap water costs an average of 2.71 euros per cubic metre including taxes, or about 0.27 cents per litre, according to the tariff overview from Vewin. The water itself is therefore negligible in cost; you are paying almost entirely for the filtration. And compared with bottled water, every form of filtering stays favourable: according to Milieu Centraal, a glass of bottled water puts 100 to 200 times more strain on the environment than a glass of tap water.

9. Buying advice: which type suits your situation?

Choose a gravity filter if…

• you want an emergency supply that works if the tap or the power grid fails;
• you live or stay somewhere without a fixed water connection: campervan, boat, tiny house, allotment;
• you want to make rainwater or surface water drinkable;
• you cannot or would rather not drill in the kitchen, and you want to be able to take the device with you.

Choose an under-sink filter if…

• you want filtered water every day and would rather not refill or wait;
• you want to filter specifically for PFAS, heavy metals, microplastics and pharmaceutical residues, with independent certification;
• your worktop needs to stay clear;
• you want your water to taste not only cleaner but also softer and richer in minerals.

At PureFilter we see in practice that many people with both needs end up with a combination: a compact gravity filter in the emergency store for when things go wrong, and a fixed filter for every day. If you are only after the latter, you will find the options in our overview of a water filter for the home or in the comparison on the best water filter page.

10. Frequently asked questions

11. Conclusion

A gravity water filter is a strong piece of engineering for a specific problem: making water drinkable without electricity, without pressure and without a connection. As an emergency supply, in a campervan or on a boat there is little that can match it, and the better models with ceramic or ultrafiltration down to about 0.03 micron do precisely what they promise.

For everyday tap water in a Dutch kitchen the sums work out differently. According to the RIVM, the water from your tap meets the standards in more than 99.9 per cent of measurements, so the gain is not in bacteria but in what is dissolved in it: PFAS, heavy metals, pharmaceutical residues, microplastics. That is exactly where a gravity filter is weakest, and on top of that you pay in time: refilling, waiting, cleaning.

So if you are not looking for an emergency solution but simply for better drinking water every day, a fixed filter is the logical step. The PureFilter Mineral+ costs 149.00 euros including the first filter, is certified to NSF 42, 53, 61 and 372, filters more than 100 contaminants and adds calcium, magnesium and potassium back via Swedish Mineral Rock™. One filter lasts 15,000 to 20,000 litres, installation takes 5 to 10 minutes without a plumber, and the 65.00 euro replacement filter works out at less than one cent per litre. If it does not suit you, there is a 40-day free return period and a 5-year guarantee.