Water Quality

Yes, you can drink the tap water without hesitation.

A working group at ETH Zurich has identified that, after standing still for a prolonged period, drinking water may slightly exceed thresholds for lead and nickel. However, due to the low quantities involved, there is no appreciable risk to health. We recommend flushing taps until the water reaches a constant temperature in order to minimise lead and nickel levels. This also helps to fight the bacteria that can develop in standing water.

There have been no such indications to date. In buildings in which elevated lead and nickel levels were detected in the autumn of 2024, 25 exposure assessments were conducted, and 64 personal consultations were carried out. In total, 13 people elected for biomonitoring. In no cases was an appreciable health impact detected ¨C including for expectant and breastfeeding mothers.

Levels slightly in excess of legal thresholds only occur in isolated cases after water has been standing still for a prolonged period ¨C and, due to the low quantities involved, do not present an appreciable risk to health. Over the long term, it is important to minimise our lead and nickel intake. We therefore recommend allowing the tap to run until the water reaches a constant temperature before drinking.

From a health perspective, you can wash your hands and brush your teeth without hesitation, also without flushing the tap first. Lead and nickel in tap water cannot enter your body in significant quantities through your skin. The tiny quantities that could enter your body while brushing your teeth are inconsequential for your health.

Certain materials used in plumbing fixtures, such as brass, red bronze and chrome plating, can release small quantities of lead and nickel when drinking water stands still. Although the lead concentration in fixtures has fallen consistently over the last 20 years, lead and nickel levels can exceed legal thresholds in isolated cases if water stands still for prolonged periods. The longer the water stands still in the pipes, and the older the plumbing system, the more heavy metals can leach out.

You can find details and results of the investigation conducted by an external plumbing engineer on behalf of ETH Zurich in this Download report (PDF, 2 MB).

No. Levels only exceed thresholds in isolated cases, and only when water has been standing still for prolonged periods ¨C as the external Download report (PDF, 2 MB) confirms.

Lead-containing fixtures ¨C such as taps, fittings and pipe connectors ¨C are widespread in Switzerland and across Europe, including in all ETH buildings. These are fixtures made from alloys such as brass and red bronze, or which feature chrome plating.

The recommendation to flush taps before use extends to all buildings. Newer fixtures and fittings also contain small quantities of lead, which can result in elevated levels if water has been standing for long periods.

Internal and external experts have attributed the fact that elevated levels have been found in some buildings but not in others to water standing still for longer in the affected pipes.  

Following isolated measurements above set thresholds in the autumn of 2024, there was a suspicion that the age of the plumbing systems could play a role. However, this was only true to an extent. In-depth investigations identified the time for which water had been standing still in the pipes as the most decisive factor. Consequently, tests for heavy metals will be conducted in all ETH buildings in the future ¨C regardless of their year of construction.

Yes. Lead-containing fixtures ¨C such as taps, fittings and pipe connectors ¨C are widespread, not only in ETH buildings but also in Switzerland and across Europe.

No. Elevated lead and nickel levels do not result in visible discolouration of water. A brown tinge in water is caused by rust.

The Water Quality working group includes experts from the Engineering & Systems, Facility Services (FS) and Safety, Security, Health and Environment (SSHE) departments, along with the water research institute Eawag. An external plumbing engineer was engaged to examine the causes and potential solutions. The engineer implemented extensive measures in two buildings (HPM & HPP) where elevated levels were identified in original samples. They also produced a report that underpins the ETH recommendations.

Our occupational health team sought advice from an ETH toxicologist in the course of the risk assessment and engaged with cantonal physicians.

Reducing potentially elevated levels of heavy metals is plain and simple: just allow the tap to run until the temperature is constant before drinking. That¡¯s why the ETH Zurich working group issued the following recommendation: ¡°Flush briefly ¨C drink without hesitation.¡±

This simple recommendation is being communicated to all members of the ETH community and publicised with posters in buildings.

Water quality in first aid rooms will be ensured at all times, including without prior flushing ¨C after measures are implemented in the months ahead.

ETH Zurich will also examine the lead and nickel levels in drinking water in all ETH buildings on an annual basis moving forward ¨C in line with existing tests for Legionella and bacteria.

The recommendations were developed by Water Quality working group, which includes experts from the Engineering & Systems, Facility Services (FS) and Safety, Security, Health and Environment (SSHE) departments, along with the water research institute Eawag. They are based on a report by an external plumbing engineer. The engineer conducted extensive measures in two buildings (HPM & HPP) in which measures levels exceeded thresholds in the autumn of 202.

Download Link to the report (PDF, 2 MB)

Yes, this is evidenced in the external report produced by a plumbing engineer following extensive measurements in two of the originally affected buildings.

Installing water filters in all buildings would not be a reasonable solution because these devices require regular maintenance and replacement. In addition, if a filter reaches capacity and no longer functions correctly, it could even lead to contaminants like heavy metals being emitted back into the water.

Completely lead-free fixtures have not yet become standard. This makes them scarce and difficult to source. In addition, fittings, pipes and joints are built into walls, which means they can¡¯t be easily replaced. In future construction and renovation projects, we will take measures to further minimise the levels of heavy metals in drinking water by using fixtures containing the lowest possible amount of lead. 

Even if we take a tap out of use, there is still water in the pipes that supply it. This standing water can absorb heavy metals. Legionella colonies can develop quickly in standing water. If these colonies are disturbed when water is removed from other taps in the system, the bacteria could spread throughout the water supply ¨C which would be counter-productive.

Eating and drinking are strictly prohibited in laboratories and workshops for hygiene and health reasons. Objects or surfaces (e.g. fittings, drinking bottles) may be contaminated with harmful substances such as chemicals or microorganisms, which can be ingested unnoticed when consuming food and pose a risk to your health.

You can find more information in the Download information sheet "Prohibition of Food in Laboratories and Workshops" (PDF, 680 KB).

There¡¯s no way to avoid a certain increase in consumption. But when it comes to frequently used sources ¨C such as in break rooms and bathrooms ¨C water isn¡¯t left standing for long. As a result, the water usually reaches a constant temperature after a few seconds, at which point you can drink it without hesitation. 

The recommendation to let taps run briefly before drinking the water is being communicated to staff, students and guests via posters in all ETH Zurich buildings. We will also raise awareness through the Internal news page, a website featuring FAQs, the VS-ETH newsletter and targeted emails to people in buildings where elevated heavy metal levels were detected in the autumn of 2024.

In older buildings, rusty water can sometimes come out of taps ¨C especially if water has been standing still for a prolonged period or building work is underway. If water is discoloured, you should flush the tap until the water runs clear.

Not necessarily. Lead and nickel are not visible in drinking water. Discoloured water is caused by rust. However, discoloured water does not satisfy the requirements of drinking water as defined in the external page Swiss FDHA Ordinance on Drinking Water . Let the water run for a few minutes until it runs clear before drinking.

Enter the precise location and describe the problem in the Facility Services reporting portal. The report will be forwarded to the relevant service area, who will look into the issue.

As a fundamental rule, you should not drink hot tap water because it may have been standing still in boilers for a prolonged period. When preparing tea and other hot drinks, you should use cold tap water and then heat it as required. This is particularly relevant when preparing baby food.

Easy-to-apply instructions (¡°Flush briefly, drink without hesitation¡±) will be communicated comprehensively and repeatedly to the ETH community. ETH Zurich will also examine the lead and nickel levels in drinking water in all ETH buildings on an annual basis moving forward ¨C in line with existing tests for Legionella and bacteria.

Measures will also be implemented in future construction and renovation projects to further minimise the potential for heavy metals to leach into drinking water.

The water dispensers installed as a precaution in the autumn of 2024 will be removed because testing has shown that tap water quality is impeccable following a brief flush. We are informing the users of these buildings. The elevated levels were caused by water standing still for prolonged periods.

Yes. This is a statutory requirement and is carried out on an annual basis.

The legal maximum levels of heavy metals are set out in external page in the Swiss FDHA Ordinance on Drinking Water and Water in Public Baths and Shower Facilities (available in DE/FR/IT only).

The limits are:    

• Lead: max. 0.01 mg/l
• Nickel: max 0.02 mg/l