Where does our drinking water come from? Origin, treatment, quality

Four sources of raw water sustain Germany's drinking water supply. The UBA report for 2022 covers 2,507 water supply areas. An area is included as soon as more than 1,000 m³ of drinking water per day is distributed there or more than 5,000 people are supplied. These areas are home to 74.1 million people, i.e. 88.6% of the population.

The picture varies greatly from region to region. Bremen, Hamburg, Saarland and Schleswig-Holstein rely 100% on groundwater. Brandenburg is at 93.4%, Berlin at 32.0%. Thuringia covers 67.0% from lakes and reservoirs, Saxony 46.0% and Saxony-Anhalt 33.5%. Berlin draws 56.0% from bank filtrate, North Rhine-Westphalia 31.0% through groundwater recharge. So anyone asking where their own water comes from only gets the answer at the level of the supplier.

Under § 2 TrinkwV, drinking water is water intended for human consumption, either in its original state or after treatment. The ordinance names five uses: drinking, cooking, preparing food and drinks. These are joined by personal care and cleansing as well as the cleaning of objects in contact with food or in lasting contact with the body. The physical state and the means of transport play no role.

A central water supply system starts at 10 m³ of drinking water per day. Below this threshold, other rules apply, for example for building systems and small systems. The actual requirement is laid down in the Infektionsschutzgesetz (IfSG, German Infection Protection Act). § 5 TrinkwV deems § 37(1) IfSG to be met when three conditions come together. The generally recognised rules of technology are complied with, the requirements of §§ 6 to 9 are fulfilled, and the water is pure and fit for consumption.

Treatment follows an exhaustive list of permitted purposes. § 18 TrinkwV names four: removal of substances and particles from the raw water, removal of solids in the drinking water installation, modification of the physicochemical composition, disinfection. Anything not on the list is not permitted.

The third purpose is the least conspicuous and, in practice, the most important. It permits four interventions: ensuring compliance with the requirements up to the draw-off point, adjusting corrosion-chemical properties, detecting leaks, and adjusting the calcium and magnesium content. This means that water is treated even when it already complies with all limit values. The reason is the pipe: aggressive water dissolves metals from the material, and corrosion eats away at the network's substance.

Three rules place additional limits on the process. § 19(2) states the first one concisely. Verbatim: “Substances other than treatment substances must not be added to raw water and drinking water.”

Only substances and disinfection processes from the UBA list under § 20 are permitted. Under § 19(6), treatment substances must be completely removed at the end, unless they are expressly intended to remain in the water.

Unavoidable residues must meet three conditions. They must be technologically inactive and harmless to health in the quantities present. Colour, odour and taste must not suffer as a result. If a supplier uses a new treatment substance, it must inform consumers of this in writing under § 26, including its concentration in the drinking water. For central systems, an announcement in local daily newspapers is sufficient, which is why such notices are easily overlooked.

Chlorination is worth putting into context. Disinfection is one of the four permitted purposes, but it is not standard: where the raw water is well protected, waterworks operate without it. Details can be found in the guide on chlorine in drinking water.

In 2022, the supply was ensured by 5,599 water suppliers. 4,155 of them abstracted the water themselves and operated over 15,200 water abstraction facilities for this purpose. According to the Bundesverband der Energie- und Wasserwirtschaft (BDEW, German Association of Energy and Water Industries), the distribution network downstream is around 544,000 km long (as of 2020). In 2022, around 4.67 billion m³ went to end consumers, 81.5% of it to households and small businesses.

What matters is where the limit values apply. § 10 TrinkwV requires compliance “at the outlet of the drinking water draw-off points”, i.e. at the tap and not at the outlet of the waterworks. The requirement therefore explicitly covers the last few metres through the building.

From the house connection onwards, the owner is liable, not the supplier. The drinking water installation in the building falls within the responsibility of the connection holder. There, three factors determine quality: the pipe material, the age of the pipes and how long the water stands in them. Since 12 January 2026, lead has been completely banned under § 17 TrinkwV. Galvanised steel pipes and old copper pipes remain an issue. Water that has been standing in the pipe overnight absorbs more from the material than freshly drawn water. Then there is temperature. Legionella find the best conditions between 25 and 45 degrees Celsius. § 31 TrinkwV therefore provides for specific testing obligations for Legionella spec.

A filter at the draw-off point targets precisely the section that no supplier can reach. Which cartridge performs which task is shown in the overview of drinking water filters. The supplier remains responsible for the network upstream, and its figures are public.

At least once a year, the operator must inspect the protection zones of its system. § 27 TrinkwV requires it to check for circumstances that were previously unknown to it and that may impair quality. If anything is noticed, adapted tests of the raw water follow. The results must be documented in writing and kept available for ten years. If no protection zones have been designated, the obligation applies to the area surrounding the water intake.

Since the 2023 version, a second instrument has been added. § 34 TrinkwV obliges operators of central systems to carry out continuous risk management across the entire chain. Two deadlines apply: by 12 January 2029 for systems with more than 100 m³ per day or more than 500 people supplied, and by 12 January 2033 for smaller ones from 10 m³ or 50 people. After that, the risk management must be reviewed at intervals of no more than six years.

Both obligations explain the high quality better than spot checks alone. It is not only the measured value at the tap that is monitored, but also the catchment area upstream.

Over 99% of the samples tested comply with the legal requirements, and this applies to almost all microbiological and chemical quality parameters. This is how the UBA report for the period 2020 to 2022 sums it up. The assessment refers to the supply areas subject to reporting, i.e. to 88.6% of the population.

The report becomes specific regarding active substances in plant protection products and biocides. Of 349 active substances and metabolites tested, 14 exceed the limit value of 0.00010 mg/l in up to 1% of the samples tested for them. The report concludes that this does not pose a health risk, because for precautionary reasons the limit value is far below the toxicologically derived concentration.

Two caveats apply to this rate. Small areas below the reporting threshold are missing from the statistics, as is domestic plumbing as a source of problems in its own right. And a rate of over 99% does not mean zero: individual exceedances do occur, and the reporting and action obligations described below apply to them.

Under § 46 TrinkwV, the operator of a central system must provide seven items of information on a website. This turns your own water quality into a question of knowing the right address rather than of research.

Incidentally, the third item answers the most common practical question. Anyone who wants to know whether their water is hard or soft will find the value there rather than on a test strip. What hard water means in practice is explained in the guide on limescale in water.

In 2022, water supplied amounted to 126 litres per inhabitant per day. The figure is the quantity delivered by the suppliers per inhabitant, not household consumption measured at the tap. It is falling over the long term: in 1991 it stood at 144 litres, in 2010 and 2013 at 121, in 2016 at 123 and in 2019 at 128 litres.

In 2022, 99.5% of households and small businesses were connected to the public network, compared with 97.9% in 1991. Of the roughly 4.67 billion m³ of water supplied, 3.80 billion m³ went to households and small businesses and 862 million m³ to large commercial consumers. The share that is actually drunk amounts to a few litres per person per day.

Two thirds of Germany's drinking water comes from groundwater, the rest from lakes and reservoirs, recharged groundwater and bank filtrate. Treatment is restricted to four purposes and a positive list. Over 99% of samples meet the requirements, measured in areas covering 88.6% of the population.

Responsibility is divided along a clear line. Up to the house connection, it lies with the supplier, who must publish its values under § 46 TrinkwV. From the house connection onwards, it lies with the owner, while the limit value under § 10 TrinkwV nevertheless only applies at the tap. If you want to know your own figures, start with your supplier and then look at the material and age of your own pipes and how long water stands in them.