Water filter system: countertop or under sink?

Reading time: ~12 minutes

What is a water filter system?

The term water filter system is attached to at least five different products in Dutch webshops: a jug with a cartridge, a glass or steel jug that works on gravity, a clip-on unit for your tap, a fixed filter in the cold water line and a reverse osmosis unit with a storage tank. They share a name and they do not do the same thing. That is exactly why this choice feels so difficult.

The distinction between on and under is more useful than the distinction between brands, because it immediately fixes three things: the volume of filter material, the contact time between water and filter, and whether you have to operate the system yourself every day. If you would like to take a step back first and see which water filter types exist on and under the counter, that overview is on our filter page.

Countertop or under sink: the real difference

The difference is not in the filter technology. Activated carbon is in both. The difference is in three measurable properties, and those three explain almost every performance difference you see in tests.

Volume of filter material. A cartridge in a filter jug usually weighs a few tens of grams. A cartridge in an under-sink housing is a cylinder ten to twenty centimetres tall with considerably more carbon material inside. More material means more adsorption capacity before the filter is saturated, and therefore more litres per cartridge.

Contact time. In a jug the water drops through the cartridge in seconds, driven by nothing more than gravity. In an under-sink system the water is pushed through a longer column of filter material by mains pressure. With adsorption the rule is: the longer the water touches the carbon, the more stays behind. It is the same reason a slow drip coffee machine brews a stronger cup than a fast one.

Number of actions. A 2.4 litre jug in a household that drinks and cooks with three litres a day quickly means two filling rounds a day. That is well over 700 actions a year. An under-sink system asks for none, because the water flows through by itself as soon as you open the tap.

That third one is the decisive one in practice. At PureFilter we see that customers who switch from a jug to a fixed system almost never do so because the jug did not work, but because nobody felt like filling it any more. A filter standing on the countertop waiting for someone to top it up is filtering nothing at that moment.

Why the location of the filter matters

Dutch tap water is not a problem that needs solving. The most recent ILT assessment published by Vewin, the Dutch association of water companies, shows that water companies carried out 559,933 measurements and that 99.9% of the samples met the legal standards. In 502 cases they did not, and in 90% of those it concerned substances with no direct danger to public health. Anyone buying a filter to make unsafe water safe is solving a problem that does not exist.

More interesting is where the exceedances that did occur were measured. In 19 cases of exceeded standards it concerned legionella growth, and according to that same assessment those were all measured at the tap, in the internal plumbing of the customer. Not in the distribution network of the water company, but in the pipes behind the front door.

That is the argument for the location of your filter in one sentence: the water company delivers up to your water meter, and everything that happens after that happens in your home. The same logic applies to lead. According to the RIVM, the Dutch National Institute for Public Health, buildings from before 1960 may still contain lead pipes that release lead into the tap water, and the advice is to have them replaced. A filter as close to the tap as possible catches what is only added to the water in your own internal plumbing. A jug you fill from that same tap does so too, by the way, as long as you keep filling it.

Water filter system on the countertop

Everything that stands apart from the plumbing falls into this category. There are three variants, and they differ considerably from one another.

The filter jug

The cheapest entry point, usually 20 to 40 euros for the jug and 4 to 8 euros per cartridge. A jug mainly tackles chlorine, taste and odour and is therefore a taste improver. The cartridge normally lasts four weeks, regardless of how much you draw, because the ion exchanger inside saturates over time. If you want to know how strict that interval is, you can read how often you replace a Brita filter. The brand Aquaphor sits in the same segment with a slightly different cartridge build; we looked separately into what Aquaphor water filters do and do not do.

The gravity or dispenser system

A steel or glass tank with ceramic or carbon candles inside, usually 8 to 14 litres, which you fill at the top and through which the water slowly descends. This is the type most often promoted as a water filter system in Dutch search results. The advantage is the contact time: hours instead of seconds, and that is a genuine technical advantage. The drawbacks are the footprint on your countertop, the weight when filling and the price, which with the well-known brands quickly exceeds 300 euros. We reviewed the ceramic gravity filter from British Berkefeld separately, and explained more generally how a water dispenser works.

The tap-mounted filter

A cap you screw onto the spout of your tap, with a small lever to switch between filtered and unfiltered. No refilling, but a small cartridge and a noticeably lower flow rate. On top of that it does not fit every tap spout by a long way, and on a modern pull-out kitchen tap almost never.

Where countertop systems are strong

• Low entry price: you start for less than 50 euros.
• No connection needed: you do not touch your plumbing, which is convenient in a rented home or a temporary situation.
• Moves with you: out of the cupboard, into the box, done.
• No installation: unpack, rinse, fill.

Where they fall short

• Refilling: the main reason jugs end up in a cupboard.
• Space: a 12 litre dispenser permanently takes over a corner of your worktop.
• Cost per litre: four cartridges a year at 6 euros over roughly 1,500 litres comes to a good one and a half cents per litre, more than with a fixed system.
• Only what you pour in: your pasta water, your coffee machine and your kettle get unfiltered water, unless you fill those from the jug as well.

Water filter system under the sink

An under-sink system is built into the cold water supply of your kitchen tap. It sits in the cabinet under the sink, you see nothing of it, and all the cold water you draw is filtered. Within this category there are two main variants, and the difference between them is bigger than many webshops let on.

Inline filtration

The water passes through one or more filter cartridges on mains pressure and comes straight back out. No electricity, no storage tank, no waste water. The flow rate stays close to that of your ordinary tap, which means your pan fills in the normal amount of time. The PureFilter Mineral+ works this way, with five filter stages and a mineralisation stage as the last step.

Reverse osmosis

A membrane system that forces water through a very fine membrane. It removes a lot, but in return it requires a storage tank that takes up a good part of your cabinet, often a power socket, and it flushes part of the water away as concentrate. It also removes the minerals you do want to keep in your water. We described in detail what a Waterdrop osmosis system asks of your kitchen and where that difference pinches in practice.

Where under-sink systems are strong

• Zero actions: opening the tap means filtered water, for cooking, tea and the kettle too.
• More filter material: a cartridge good for 15,000 to 20,000 litres against a jug cartridge good for a few hundred.
• Out of sight: your worktop stays clear.
• Lower price per litre: with the PureFilter Mineral+ the replacement filter costs €65.00, and across that capacity that works out at less than one cent per litre.
• Combines with a Quooker: the filter goes before the Quooker system on the cold water supply, and there is more about that on our page about the Quooker water filter.

What to take into account

• One-off installation: 5 to 10 minutes on the cold water line. You do not need a plumber; for the installation you use one pair of water pump pliers, and you change the cartridge later with the supplied key.
• Connection size: a 3/8 connection is supplied as standard. If your tap has a different size, an adapter is needed.
• Space in the cabinet: an inline filter fits almost always; an osmosis system with a storage tank far from always.
• Higher purchase price: you start higher than with a jug, but you end up lower per litre.

If you want to see what that installation looks like step by step before ordering, our piece on how to install a water filter yourself has the complete sequence, including what to do if the tap connection is different.

The two side by side

What does a water filter system cost per litre?

The purchase price says little; the price per litre says everything. Work it out with the two figures you can always find: the price of a replacement cartridge and its capacity.

With a filter jug you normally buy twelve to thirteen cartridges a year if you keep to the four-week interval. At 6 euros each that is 72 to 78 euros a year. If you drink and cook with three litres a day, that is a good 1,000 litres, and you end up at roughly seven cents per litre. If you barely fill the jug, that price per litre only goes up, because the cartridge expires on time rather than on use.

With the PureFilter Mineral+ the replacement filter costs €65.00 and covers 15,000 to 20,000 litres. That is €0.0033 to €0.0043 per litre, or less than one cent. For comparison: a litre of bottled water costs 40 cents to a euro. The duo with two cartridges costs €115.00. If you would rather not think about it at all, the Filterplan sends the filters automatically and on time, for €48.00 with 1 to 3 people or €86.00 with 4 to 6 people; individual filters remain available to order as usual.

On top of that, tap water itself costs almost nothing. We worked out exactly how that sum runs in our piece on what a cubic metre of water costs. And purely on environmental impact the comparison is not even close: according to Milieu Centraal, the Dutch information body for sustainability, the climate impact of one glass of bottled water is comparable to roughly 70 glasses of tap water.

What should you look at when choosing?

Certification, and the difference between 42 and 53

This is the most useful filter against marketing language there is. According to NSF International, NSF/ANSI 42 covers aesthetic effects such as chlorine, taste, odour and iron, and NSF/ANSI 53 covers health-related substances such as lead, volatile organic compounds and cryptosporidium. A system with 42 only is a taste improver. If you want health-related substances to be reduced as well, you look at 53. The PureFilter Mineral+ is certified to 42, 53, 61 and 372, where 61 covers material safety and 372 covers lead-free material.

Flow rate

With an under-sink system this is the objection that comes up most often: will my tap run more slowly? With inline filtration the difference is limited and you mainly notice it when filling a large pan. With osmosis and a storage tank the difference is large, because you then draw from a tank that has to refill. If you want to know where you are starting from, first measure how many litres per hour come out of your tap.

The replacement moment

A saturated filter holds nothing back any more, and that is the only scenario in which a filter is worse than no filter. So choose a system whose interval you can remember. With the Mineral+ the lifespan depends on household size: roughly twelve months with 1 to 3 people, roughly six months with 4 to 6 people. How that works out for other types is in our overview of how often you replace a water filter.

Are you staying put?

The only question on which a countertop system objectively scores better. If you live somewhere temporarily, rent furnished or move within a year, a jug or dispenser is the wiser choice. If you are staying put, the installation is a one-off ten-minute job against hundreds of filling rounds a year.

Whole house, campervan and emergency kit

Anyone searching for a water filter system also runs into three adjacent situations. Each one calls for something different, and it is fairer to say so plainly.

For the whole house. A system on the main line filters all the water in your home, so your shower, washing machine and toilet as well. That means much larger housings, a connection to the main supply and, in most cases, an installer. For drinking water it is unnecessary, because you would be filtering hundreds of litres a day of which you drink three. We do not supply this type.

In a campervan or caravan. Here it is about a tank that stands still, and standing still is a different problem from contamination. A compact inline filter with a disinfecting action makes more sense then than a drinking water filter for the home.

In an emergency kit. If a pipe bursts or a boil water notice is issued, a fixed system does not help you, because it is attached to a line that is delivering nothing at that moment. That calls for a portable filter. We have set out what you need in an emergency kit, including how much water to count on per person.

Which system suits which situation?

Four situations, four answers.

• You simply want your water to taste better and you live somewhere temporarily: a filter jug. Low threshold, and you take it with you.
• You care about taste but do not want to touch any plumbing and have space to spare: a gravity system on the countertop. Long contact time, but count on a sizeable footprint and a higher price.
• You live somewhere permanently, drink and cook with tap water daily and do not want to think about it: an inline system under the sink. This is the situation in which the sum comes out most clearly.
• You want to remove as much as possible and accept a storage tank, electricity and waste water: reverse osmosis. Bear in mind that the minerals disappear as well.

If you are in the third group, the follow-up question is which fixed system. For that we have set the types side by side in our overview of the best water filters under the sink, and what we stock in under-sink filters is visible at a glance in the collection. If you are still hesitating between categories, our comparison of the best water filter will take you further.

Concretely: the fixed filter that is mounted under your sink costs €149.00 including the first cartridge, removes more than 100 contaminants including PFAS, microplastics, heavy metals, fluoride, nitrates, pharmaceutical residues and chlorine, and as a final step returns calcium, magnesium and potassium through Swedish Mineral Rock™. With 40 days free returns and a 5-year warranty you can try at home, in your own time, whether you taste the difference.

Frequently asked questions

Conclusion

The choice between a water filter system on or under the counter is not about filter technology but about three practical things: how much filter material fits inside, how long the water stays in contact with it and how many actions it costs you per day. On those three points a fixed system under the sink wins, and the third is in practice the reason jugs end up in a cupboard.

Put the figures next to each other and the picture sharpens. A jug costs roughly seven cents per litre, an inline under-sink filter less than one cent. A jug cartridge does a few hundred litres, an under-sink cartridge 15,000 to 20,000. And the only part of your water chain you have any influence over is exactly the stretch behind the water meter: that is where the legionella exceedances reported by Vewin were measured, and that is where the lead pipes sit that the RIVM flags in buildings from before 1960.

The countertop genuinely wins on one point, and that point is not trivial: it costs you nothing to start and it moves house with you. If you live somewhere temporarily, choose that. If you are staying put, the ten-minute installation is a one-off price for hundreds of filling rounds you no longer do, and the PureFilter Mineral+ delivers filtered and mineralised water from the tap you already have.