Rust in Tapwater: dangerous or not? 

Is the water in your tap suddenly turning brown? Then rust is most likely the culprit. The unappetizing color and metallic taste mean that many people no longer drink this water, thinking it is unhealthy. But is that really true? We explain!

In this Guidebook you will learn...

• ... how rust occurs in drinking water in the first place, 
• ... how to recognize rust particles in water, 
• ... the limit values for iron in drinking water in Germany, 
• ... the dangers of brown Tapwater ,
• ... whether rusty water is a reason to reduce the rent
• ... and what you can do against rust water. 

How does rust form in drinking water? 

Rust is a product of corrosion. It is caused by the oxidation of iron or steel in the presence of water. The oxygen in the water reacts with the iron in the pipes, creating iron hydroxide, which is deposited on the walls of the pipes. This iron hydroxide reacts further with the oxygen in the water and eventually rust forms. If the rust formation is more advanced, the rust particles dissolve and get into the water. The result is brown Tapwater. 

There are many causes of rust in water. This process occurs most frequently in galvanized iron or steel water pipes. Over the years, the protective zinc coating wears off and is removed. This exposes the underlying iron and the pipe begins to rust. Old cast-iron water pipes or pipes made of mixed materials are just as susceptible. 

However, prolonged stagnation or high temperatures can also stimulate rust formation. Particular care should be taken if you have your own well water supply, as this can also lead to rust in the water. Rusty water can also occur briefly during maintenance work on the drinking water pipes or pressure fluctuations in the pipes. 

Causes of rust in water

• Poorly galvanized steel pipes
• Natural erosion of the zinc coating over time
• Old cast-iron water pipes
• Pipes made from mixed materials
• Long periods of stagnation 
• High temperatures 
• Water supply from our own well
• Maintenance work on the drinking water pipes
• Pressure fluctuations in the line

How do I recognize rust water? 

The most reliable sign of rusty water is its brown color. The only other reason for brown water from the tap is a high concentration of manganese. You can also recognize rusty water by its typical metallic taste and possibly unpleasant smell.

Rust and other heavy metals

Once rust is in the water, there is a risk that other heavy metals will also get into the drinking water due to corrosion. The problem is that, unlike rust, this can pose a health risk. For example, a high concentration of lead in the water is particularly undesirable. High doses of copper can be just as dangerous for babies and children.

Rusty water: limit values in Germany

The German Drinking Water Ordinance regulates the quality of our tap water ¹. It specifies various limit values that must not be exceeded and must be checked regularly. These include iron, which is responsible for rusty water. Its limit value is 0.2 mg per 1 liter of water. 

Iron is naturally contained in our Tapwater. However, from 0.5 mg iron in the water, there are changes in taste and the characteristic brown coloration ². The cause of this increased value usually lies in the in-house pipelines and not in the general water supply network. 

Is rust in water harmful to health? 

In principle, rusty water is not dangerous because our body simply excretes the excess iron. It is even an important trace element for the human organism. The daily requirement for adults is approx. 10-15 mg per day and for pregnant women even up to 30 mg per day ³. 

Iron only becomes a health hazard at very high doses, which rusty water generally does not reach. As a rule, an excess is only achieved by taking iron supplements over the long term and not as prescribed by a doctor ⁴. In such a case, there is a risk that the iron will be deposited in organs such as the liver, spleen or heart and cause damage there. 

Disadvantages of rust in water pipes

Even if rusty water is not harmful to our health in principle, you should still eliminate the problem as quickly as possible. This is because it is a clear indication of defective water pipes or soldered joints and can have numerous other disadvantages, including

• Pipe bursts
• Release of heavy metals (e.g. lead, copper, zinc)
• Colonization of bacteria and germs that need iron for metabolism
• Red-brown stains in freshly washed laundry
• Damaged and consequently leaking seals
• Clogged strainers in washing machines and dishwashers
• Blocked pipes

Even if rust in water is not a health risk per se, you should definitely have this clarified in order to avoid the side effects mentioned above. 

Rust in the water: what to do? 

If water pipes are not used for a long period of time, rust can occur under certain circumstances. This is the case, for example, in empty houses or apartments or if water pipes have been temporarily turned off due to building work or similar. You should therefore drain the water for a few minutes after a long period of inactivity. This will simply flush out the rust particles and you can then enjoy rust-free water. 

If the problem is deeper and the cause is damaged pipes, the water pipes should ideally be renovated with corrosion-resistant materials. Another option is to use chemical agents consisting of phosphates and silicates. For this purpose, a dosing device is installed in the pipe, which gradually releases the substances. These form a protective layer in the water pipes and thus prevent the further formation of rust. 

Drinking water filters are another alternative. High-quality activated carbon block filters or filters with quartz sand are able to filter rust particles out of Tapwater and provide you with clean drinking water. The advantage of water filters: in addition to rust, they also remove heavy metals and other undesirable substances from your drinking water. 

Rusty water in the rented apartment: right to a rent reduction?

In principle, the house or apartment owner is obliged to check the quality of the drinking water if it is not in perfect condition. If it turns out that the Tapwater does not comply with any limit values, the landlord must rectify the problem. The landlord usually has to pay the costs of pipe renovation himself. 

Until this defect is rectified, tenants may be able to claim a rent reduction. There is always a right to a rent reduction if the rented apartment does not correspond to the condition agreed in the contract or if its use or suitability for living is significantly restricted by a defect ⁵. Whether this applies to rusty water depends on the individual case. 

In order to achieve a rent reduction, a notice of defects must be submitted to the landlord. In the end, the reduction usually amounts to 10-15%. However, the exact amount and whether this is actually granted varies from case to case. The chances are poor, for example, if the problem only occurs after prolonged stagnation and is rectified after the water has drained away for a short time. 

No more brown water from the tap! 

Rust in water is not dangerous for our health per se, but most people still don't want to drink it. This is mainly due to the unappetizing discoloration and unfamiliar taste. 

Although rusty water is toxicologically harmless, you should still take action if the water in your pipes is brown. This is because corroded water pipes can have numerous other undesirable consequences. In such a case, you will probably not be able to avoid renovating the pipes. If the reason for the rusty water lies elsewhere, a water filter can help. It cleans the drinking water in no time at all so that you can enjoy clean water again.

Questions and answers

What happens when you drink water containing iron? 

As a rule, nothing unusual happens when you drink water containing iron. This is because, despite the increased concentration, there is normally still too little iron in the water to be dangerous for the human body. Some of the trace element is absorbed by your body and excess iron is simply excreted. 

Can rusty water be filtered? 

Yes, high-quality activated carbon block filters and water filters with quartz sand in particular can be used to filter rust particles out of drinking water. After the filtering process, the water should return to its usual color and original taste. 

Is rust in water harmful to plants? 

No, rusty water is generally just as harmless to plants as it is to humans. 

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