Why filter water: reasons, benefits and limitations
At the waterworks, tap water complies with the limit values in over 99% of cases. The supplier's responsibility ends at the house connection. What a filter does beyond that point.
According to the federal report for 2020 to 2022, German tap water meets the limit values in over 99% of cases for almost every parameter. For nitrate the figure is 99.97%, for pesticides in 2022 a full 100%. The reason for a filter therefore lies elsewhere: the supplier's responsibility ends at the point of delivery in the basement. For nickel, the federal authorities attribute 92 of 202 exceedances to the plumbing in the building, for lead 71 of 215. This guide explains where a filter works, where its limits lie and which households it is worthwhile for.
The short answer
A filter at the tap is worthwhile above all where the pipes in the building are old, long or rarely used. At the waterworks, the German supply delivers top results. According to the Statistisches Bundesamt (Federal Statistical Office), 5,599 suppliers delivered 4.67 billion cubic metres of drinking water in 2022. Of this, 3.80 billion went to households and small businesses. A considerable share of the exceedances only arises after that point, 38.3% in the case of metals.
In new buildings with short pipe runs and daily use, on the other hand, the added benefit remains small. The honest answer distinguishes between the two cases instead of issuing blanket warnings. Which case applies depends on the year of construction, the length of the riser and how often the tap is used.
What the 2025 federal report says about water quality
Every three years, the Bundesministerium für Gesundheit (Federal Ministry of Health) and the Umweltbundesamt (German Environment Agency) publish a joint report. The current edition was published in February 2025 and covers 3 years, namely 2020 to 2022. It is based on reports from the federal states covering 2,507 areas. For the 2022 reporting year, the figures are as follows:
| Parameter | Tests | Compliance rate |
|---|---|---|
| Escherichia coli | 118.344 | 99,97 % |
| Enterococci | 72.838 | 99,89 % |
| Nitrate | 18.843 | 99,97 % |
| Lead | 14.573 | 99,58 % |
| Nickel | 14.581 | 99,57 % |
| Copper | 14.042 | 99,89 % |
| Total pesticides | 4.524 | 100,00 % |
These values are high, and they come from the authorities themselves. A guide claiming the opposite is working against the evidence. What matters is where the authorities measure and how far their responsibility extends.
In 2022, the raw water consisted of 67.6% groundwater, 15.9% surface water, 8.7% artificially recharged groundwater and 7.8% bank filtrate. Treatment at the waterworks depends on the origin of the raw water. A waterworks using bank filtrate works with more stages than one using deep groundwater.
Where the water supplier's responsibility ends
The point of delivery is where drinking water passes from the network into a building's drinking water installation. It is usually located at the water meter in the basement. Up to that point, the supplier is responsible for 3 steps: abstraction, treatment and distribution. This is how the Trinkwasserverordnung (German Drinking Water Ordinance) describes it in its section on risk management.
From the meter onwards, the owner of the building is liable. Pipes, soldered joints, taps and hoses belong to them. For a block of rented flats, this means the supplier delivers water in perfect condition up to the basement wall. The stretch up to the flat on the third floor belongs to the owner.
Beyond the meter, the Ordinance has a separate category. Annex 2 Part II is headed “Chemical parameters whose concentration may increase in the distribution network, including the drinking water installation”. It lists 15 substances, including lead, copper, nickel, antimony, arsenic, cadmium, bisphenol A and trihalomethanes. The legislator itself therefore expects values to rise over the last stretch.
Domestic plumbing in the federal figures
The federal report has a separate column for exceedances attributable to inadequate plumbing in the building. Over the 3 reporting years, the totals are as follows:
| Parameter | Exceedances 2020 to 2022 | of which domestic plumbing | Share |
|---|---|---|---|
| Nickel | 202 | 92 | 45,5 % |
| Lead | 215 | 71 | 33,0 % |
| Copper | 50 | 16 | 32,0 % |
| Enterococci | 253 | 17 | 6,7 % |
| Escherichia coli | 110 | 6 | 5,5 % |
For the three metals, a combined 179 of 467 exceedances originate in the building, i.e. 38.3%. The report names the cause clearly. There, exceedances for lead are regarded as an indication of existing lead pipes in the building. As a second cause, it cites taps that do not meet the generally recognised rules of technology.
For nickel and cadmium, the report gives the same reason. It adds a practical note: residents often install taps themselves, bypassing a specialist company. According to the report, cadmium exceeds the limit value only in buildings.
A filter at the tap targets precisely the section beyond the point of delivery. It does not replace the renovation of old pipes or an inspection by a specialist company.
Who the federal report leaves out
A water supply area becomes subject to reporting as soon as it supplies more than 5,000 people or delivers more than 1,000 cubic metres per day. In 2022, this applied to 2,507 areas with 74.06 million people. That corresponds to 88.55% of the population.
The remaining 11.45%, around 9.6 million people, live in smaller areas. The same Ordinance applies to them, but the federal report leaves out their figures. Anyone living in a village with its own spring will therefore find the federal figures only partly applicable to them.
Then there is the type of sampling. The authorities take spot samples at four points: at the waterworks, in the network, at the point of delivery and at the tap. An individual flat is not covered by routine monitoring.
5 evidence-based reasons for a water filter
The following five reasons are based on the Ordinance of 20 June 2023 and the federal report of February 2025. Each point comes with a verifiable figure or a reference in the legal text. Speculative arguments are left out because they harm the cause.
Reason 1: Responsibility ends at the house connection
The supplier is liable up to the point of delivery, the owner after that. For tenants, the crucial stretch is therefore outside their control. They live in a building whose pipes were chosen by the owner, who alone may replace them. A filter at the tap is the one point they can decide on themselves.
Reason 2: A large proportion of metals comes from the building
For nickel, 45.5% of the exceedances from 2020 to 2022 are attributable to the plumbing in the building. For lead the figure is 33.0%, for copper 32.0%. All three values come from the federal report. More on lead, nickel and copper can be found in the guide to heavy metals in tap water.
Reason 3: Lead pipes have only been disappearing since January 2026
Section 17 of the Drinking Water Ordinance requires operators to remove or decommission lead pipes by the end of 12 January 2026. The health authority extends the deadline on application, and where the supply serves only the operator's own household, even until 12 January 2036. Some of the old pipes will therefore remain in buildings for another ten years.
Reason 4: Standing water changes the values
If water stands in the pipe for a long time, the resulting stagnant water dissolves more metal from the pipe wall and the tap. That is why the Ordinance prescribes staggered stagnation sampling with three samples for lead, copper and nickel. The limit value is deemed exceeded if just one of these three samples is above it. The effect is strongest in holiday flats, offices and rarely used guest bathrooms.
Reason 5: Stricter limit values are yet to come into force
For lead, the value of 0.010 milligrams per litre applies until 11 January 2028, after which it drops to 0.005 milligrams. The sum of 20 per- and polyfluoroalkyl substances (PFAS) has been limited to 0.00010 milligrams per litre since 12 January 2026. The stricter sum of 4 of these compounds follows on 12 January 2028 at 0.000020 milligrams. A value that is only just being met today may be an exceedance in two years' time.
What a water filter can do
An activated carbon block is a pressed filter body that works in 2 ways at once. Its dense structure retains particles mechanically. The internal surface of the carbon binds dissolved substances by adsorption. How adsorption works in detail is explained in the guide What is activated carbon.
According to the current state of the art, activated carbon binds six types of substances:
| Substance group | Origin in the water |
|---|---|
| Chlorine and its odorous compounds | Disinfection at the waterworks |
| Lead, copper and nickel | Pipes and taps in the building |
| Pharmaceutical residues | Wastewater and sewage treatment |
| Hormonally active substances | Wastewater and industry |
| Plant protection products | Agriculture, via groundwater |
| PFAS | Industry, firefighting foam, coatings |
| Particles, down to microplastics | Abrasion in the network and in the plumbing |
An additional membrane stage broadens the spectrum. Nano hollow-fibre membranes with pores of around 0.1 micrometres retain bacteria and legionella. How the other methods differ is shown in the overview of filtration technologies.
Minerals and trace elements remain in the water. This is where the activated carbon block differs from reverse osmosis, which largely demineralises the water and then remineralises it.
Where a water filter reaches its limits
6 points belong in an honest assessment of an activated carbon block. A guide that lists only advantages deserves little trust.
Nitrate remains in the water. Activated carbon binds dissolved salts poorly. Nitrate requires ion exchange or reverse osmosis. The situation across Germany is described in the guide to nitrate in groundwater and drinking water.
Limescale remains as well. Calcium and magnesium pass through the block. Anyone who wants soft water needs a separate softening system.
The service life is limited. An exhausted cartridge releases bound substances again. The replacement interval is therefore part of the filter's performance; more on this in the guide to water filter cartridges.
Standing water in the device becomes contaminated with germs. The risk is greatest with jugs and table-top devices. Details can be found in the guide to the risk of germ growth in jug filters.
Renovation remains the owner's responsibility. Lead pipes must be replaced, as the Ordinance has required since 12 January 2026.
A laboratory analysis remains the way to certainty. Anyone who suspects a specific contamination should have their water tested and act on the findings.
Together, these 6 points are the reason why blanket advertising claims harm the cause. A filter is a specialist tool for specific groups of substances, in other words the opposite of an all-purpose device.
The opposing view of the Verbraucherzentrale
The Verbraucherzentrale (German consumer advice centre) generally considers the use of filters for tap water unnecessary from a health perspective. The assessment dates from 22 April 2025. It points to the strict controls and warns of germ growth in jugs and old cartridges. It is outspoken about promises such as vitalisation or harmonisation.
Much of the Verbraucherzentrale's position is correct. It applies to the typical case. This means a household with short pipes made of new material and daily use. The federal report supports it with compliance rates of over 99%.
The two views contradict each other less than it seems. The Verbraucherzentrale is talking about the typical case, while a filter targets the exception. The trick is to assess your own household correctly.
A second piece of information comes from the same source. According to DIN 1988, a particle filter directly downstream of the water meter assembly is actually mandatory. A filter in the drinking water system has therefore long been standard; the debate is about the second stage at the tap.
4 claims fact-checked
4 claims about water filters are particularly persistent, and all 4 are wrong in their sweeping form. This fact check assesses each one individually.
“Water filters are breeding grounds for germs.” This is true of jugs with loose granules and long standing times. A block with water flowing through it and a membrane stage works differently, because there is no stored water and no stagnation. The design is what matters; the word water filter alone says little.
“German tap water is always safe.” At the waterworks, this is true according to the federal figures. For the stretch beyond that, it only partly applies. 179 metal exceedances from domestic plumbing in the years 2020 to 2022 prove this.
“Filters remove important minerals.” For activated carbon blocks, the claim is wrong: calcium and magnesium pass through them. For reverse osmosis it is true; there, remineralisation follows afterwards.
“A filter makes any water healthy.” This statement overstretches the technology. Nitrate, limescale and water hardness remain unchanged, and the only remedy for a lead pipe is to replace it.
What the colony count really tells you
Some guides to water filters cite 40,000 to 200,000 germs per millilitre of tap water. A look at the Ordinance puts this into perspective. Annex 3 sets a limit value of 100 per millilitre each for the colony count at 22 degrees Celsius and at 36 degrees Celsius. The figures cited would therefore be 400 to 2,000 times higher.
The standard is even stricter for the 2 most important germs. Escherichia coli and intestinal enterococci must be completely absent from 100 millilitres of drinking water. The limit value is 0 per 100 millilitres. In the 2022 reporting year, 99.97% of the 118,344 tests for Escherichia coli met this value.
The colony count is classed as an indicator parameter because it signals a change in the network or in the building. It serves as an early warning and, for precisely that reason, is ill-suited as a scare argument.
Who benefits most from a filter
The available data point to 6 cases in which a filter at the tap makes a measurable contribution:
| Situation | Why a filter is effective here |
|---|---|
| Buildings dating from before 1973 | Lead pipes were installed until then; 33.0% of lead exceedances originate in the building |
| Long risers from the 3rd floor upwards | more contact surface and longer residence time in the pipe |
| Holiday flat, second home or office | Standing times of several days dissolve more metal from pipe walls and taps |
| Noticeable chlorine or metallic taste | Activated carbon binds precisely the substances that cause the off-taste |
| Taps installed without a specialist company | The federal authorities attribute 45.5% of nickel exceedances to the plumbing |
| Small supply area with fewer than 5,000 people | the values do not appear in any federal statistics |
In new buildings with plastic or stainless steel pipes and daily use, on the other hand, the benefit is small. If you are unsure, ask your supplier for the current analysis and check the year in which your own pipes were installed. Both are free of charge and take just a few days.
Filtered tap water and mineral water compared
According to the Verband Deutscher Mineralbrunnen (Association of German Mineral Springs), sales of mineral and medicinal water rose to 10.2 billion litres in 2025, an increase of 2.4%. Per capita, this amounted to 128.8 litres compared with 125.6 litres the previous year. Around 150 mineral water companies share the market.
Tap water costs around 2.10 euros per cubic metre on average across Germany, i.e. about 0.21 cents per litre. A litre of branded mineral water costs considerably more, depending on the brand. The gap remains large even after deducting the cost of cartridges; the exact amount depends on service life and consumption.
| Criterion | Filtered tap water | Bottled mineral water |
|---|---|---|
| Legal basis | Drinking Water Ordinance | Mineral and Table Water Ordinance |
| Monitoring point | up to the point of delivery, spot checks up to the tap | at the source and during bottling |
| Transport route | Pipeline | Lorry, warehouse, shopping |
| Packaging | not applicable | Glass or plastic, returnable or single-use |
| Price per litre | around 0.21 cents plus cartridge | many times that, depending on the brand |
A detailed comparison of the two options can be found in the guide Tap water or mineral water.
What to look for when buying
7 criteria help with the choice, because water filters differ greatly in technology and performance:
- Filter medium. A sintered activated carbon block, loose granules and a membrane lead to very different results.
- Pore size. It determines which particles are retained and belongs in the data sheet.
- Proof of testing. A tested result for individual groups of substances carries more weight than an advertising claim.
- Replacement interval. Only the figures in litres and in months together give a complete picture.
- Installation location. Directly on the tap, under the sink or as a system for the whole house.
- Flow rate. Too low an output leads to frustration in everyday use.
- Material and take-back. A stainless steel housing lasts longer than a plastic one.
If you tick off these 7 points before buying, you will quickly see which offers have substance. If a detail is missing from the data sheet, it is worth asking the manufacturer.
Filtering water with Alb Filter
Alb Filter drinking water filters combine 2 stages in a stainless steel housing. Stage 1 is sintered activated carbon manufactured in Germany. Stage 2 is a Nano hollow-fibre membrane with pores of around 0.1 micrometres that retains bacteria and legionella. Minerals, salts and trace elements remain in the water.
As an activated carbon block filter, the device sits directly on the tap or, as an under-sink filter, under the sink, depending on the model. This places the filter at the last point before the glass, i.e. after the entire domestic plumbing. An overview of the models can be found on the drinking water filters page.
Related to this topic
Filtering water with Alb Filter
Alb Filter drinking water filters rely on sintered activated carbon Made in Germany. An additional Nano hollow-fibre membrane with pores of around 0.1 micrometres blocks germs and legionella. The solid block retains pollutants together with adhering residues and leaves minerals, salts and trace elements in the water. This way, clean drinking water comes straight from the tap. That saves lugging crates and packaging waste.
Frequently asked questions
Should you filter tap water?
There is a lot to be said for it as soon as the pipes in the building are old or long. The federal report for 2020 to 2022 attributes 45.5% of nickel exceedances and 33.0% of lead exceedances to the plumbing in the building. In new buildings with short pipe runs and daily use, on the other hand, the added benefit is small.
Do you have to filter tap water?
Legally, filtering is voluntary. The Drinking Water Ordinance requires the supplier to comply with all limit values in Annexes 1 and 2 up to the point of delivery. Within the household itself, the decision lies with the occupant. A filter is therefore an additional stage installed by personal choice.
Is filtered water healthy?
As a foodstuff, filtered tap water is safe as long as the cartridge is changed at the intended interval. An activated carbon block leaves calcium, magnesium and trace elements in the water. An exhausted cartridge, on the other hand, releases bound substances again, which is why the replacement date matters.
Do water filters make sense?
It depends on the design and the building. A block with water flowing through it and a germ barrier makes sense in an old building with long risers. An open jug with loose granules that stands on the worktop for days works against its own purpose.
Is filtered water better than tap water?
Chlorine, heavy metals from the plumbing and taste speak in its favour. For nitrate, limescale and water hardness, the result stays the same. The comparison therefore turns out differently depending on the substance.
What does a water filter filter out?
An activated carbon block binds chlorine, metals, pharmaceutical residues, hormonally active substances, plant protection products and PFAS. A membrane stage adds retention of bacteria and legionella. Dissolved salts such as nitrate pass through the block.
Do you need a water filter for tap water?
Every household is free to decide. A filter makes sense as soon as the stretch beyond the point of delivery carries risks. Typical cases are lead pipes, long standing times and self-installed taps made of unknown material.
Is a table-top water filter worthwhile?
Table-top and jug filters improve the taste and bind chlorine. Their weak point is the standing water in the container, which quickly becomes contaminated with germs at room temperature. If you use such a device, decant small quantities and put them in the fridge.
How often does the filter cartridge need to be changed?
The manufacturer's specification in litres and in months is what counts, and whichever value is reached first always applies. Exceeding the service life reverses the effect, because bound substances get back into the water.
Which water filter is the best?
The best filter only exists in relation to a specific household. 5 points are decisive: medium, pore size, tested retention, interval and installation location. A device that shines in an old building is often oversized in a new one.
How much does filtered tap water cost?
The raw material costs around 0.21 cents per litre, plus the cartridge's share. The exact total depends on the service life of the filter insert and the household's consumption.
Why do many people prefer to drink their tap water filtered?
The most common reason is taste. Residues of disinfectants and metals from old pipes create a distinct aftertaste, which activated carbon reliably binds. The guide on chlorine in drinking water shows how heavily water is chlorinated from region to region.
This is based on official reports, legal texts and data from associations. All information can be looked up at the source:
Sources
- Bundesministerium für Gesundheit (Federal Ministry of Health) and Umweltbundesamt (German Environment Agency): Report on the quality of drinking water in Germany 2020 to 2022, Environment and Health series 03/2025, published February 2025 (https://www.umweltbundesamt.de/system/files/medien/11850/publikationen/dwd_bericht_2020-2022.pdf)
- Trinkwasserverordnung (German Drinking Water Ordinance) in the version of 20 June 2023, BGBl. 2023 I No. 159 (https://www.gesetze-im-internet.de/trinkwv_2023/)
- Umweltbundesamt: Lead in drinking water (https://www.umweltbundesamt.de/umwelttipps-fuer-den-alltag/essen-trinken/blei-im-trinkwasser)
- Statistisches Bundesamt (Federal Statistical Office of Germany): Public water supply 2022, press release No. 304 of 8 August 2024 (https://www.destatis.de/DE/Presse/Pressemitteilungen/2024/08/PD24_304_32311.html)
- Verbraucherzentrale (German consumer advice centre): Water filters from a hygiene perspective, as of 22 April 2025 (https://www.verbraucherzentrale.de/wissen/umwelt-haushalt/wasser/wasserfilter-sind-sie-aus-hygienischer-sicht-notwendig-5534)
- Verband Deutscher Mineralbrunnen (Association of German Mineral Water Producers): Market data on sales 2025 (https://www.vdm-bonn.de/presse/pressemitteilungen/mineralwasser-absatz-steigt-2025-deutlich/)
