The Hidden Health Risk in Your German Apartment Nobody Warned You About

This one isn’t talked about enough. Most people who move to Germany worry about health insurance, registration, finding a flat. Nobody tells you about the thing quietly sitting in your apartment’s pipes.

Legionella bacteria. And if you’ve never heard of them — you’re not alone. But once you know, you’ll never go back from a long trip without doing this simple thing first.

What Is Legionella?

Legionella is a type of bacteria that grows in water systems — specifically in the warm, still water that sits inside pipes, water tanks, and shower heads. When the water gets disturbed — say, when you turn on the shower — tiny droplets of water become airborne, and you breathe them in.

That’s how you get infected. Not by drinking the water. By breathing the mist.

In mild cases, it causes Pontiac fever — flu-like symptoms that pass on their own. In serious cases, it causes Legionnaires’ disease, a severe form of pneumonia that can be life-threatening. The Robert Koch Institute (RKI) recorded 2,745 reported cases in Germany in 2024 alone — and the trend is rising. An estimated 2,000 people die every year from its consequences.

Germany has a lot of older apartment buildings with complex hot water systems — large storage tanks, long pipe networks, and sometimes pipes that haven’t been used in a while. That’s exactly the environment Legionella loves.

The bacteria thrive between 25°C and 55°C. German hot water systems are supposed to keep the water at 60°C or above — at that temperature, Legionella can’t survive. But if the system is old, poorly maintained, or the temperature drops somewhere in the pipes, the bacteria can multiply rapidly.

By law — the Trinkwasserverordnung (Drinking Water Ordinance) — landlords running large hot water systems (tanks above 400 litres, or pipes where more than 3 litres of water sits between the tank and the furthest tap) must test for Legionella every three years. If they find the bacteria above the permitted level, they have to fix it — and until they do, you may not be allowed to shower.

The Situation Most Expats Walk Into

Here’s when the risk is highest, and it’s a situation most of us face — coming back from a holiday, or moving into a new apartment.

When water sits still in pipes for days or weeks, it stagnates. The temperature in those stagnant sections can drift into the danger zone. The moment you turn the shower on after two weeks away, you get a face full of that water as mist.

The same applies when you move into a new flat. If it’s been vacant for a while, the water in the pipes has been sitting there. The first shower you take could be the riskiest one.

The good news is that a few simple habits significantly reduce your risk.

• After being away for more than a few days, don’t jump straight into the shower. First, open a window. Then run the cold tap for a minute or two, then the hot — let both flush through properly. Don’t stand close enough to breathe in the initial steam. Only then is it safe to shower.
• After moving into a new flat, do the same flushing process on every tap and shower before your first use. It takes five minutes and it matters.
• Regularly clean and descale your shower head. Scale buildup is a perfect home for Legionella. Unscrew it, soak in descaling solution, rinse thoroughly. Every few months is enough.
• Never use hot tap water for drinking or cooking. Always use cold water. Hot water from the boiler has a higher chance of contamination — not just from Legionella but also from pipe sediment.
• Don’t fill a humidifier with tap water. Humidifiers create exactly the kind of fine aerosol mist that carries Legionella. Use distilled or boiled water instead.

Know the Symptoms

Legionnaires’ disease usually develops 2 to 10 days after exposure. The signs are a high fever (often above 39°C), a persistent cough, shortness of breath, muscle pain, and sometimes confusion. It can look like a bad flu at first.

If you have these symptoms after returning from a trip or after moving somewhere new, mention it to your doctor — specifically say you’re concerned about Legionella. It requires a specific test and specific antibiotics. Most people recover fully with treatment, but it can get serious if it goes undiagnosed.

You have every right to ask your landlord whether the building’s hot water system has been tested for Legionella, and to see the results. In buildings that fall under the testing obligation, landlords must inform tenants of the findings. If there’s a positive result above the permitted level, the landlord is legally obligated to fix it.

If you have concerns, you can also contact your local Gesundheitsamt (public health office) — they have authority to investigate and order remediation.

Germany is genuinely one of the safest countries to live in, and most people never have a problem. But this is one of those things where knowing the basics, and following a simple routine when you’ve been away, takes almost no effort — and keeps you safe. Sources: Robert Koch Institut — Legionellosis in Germany 2024 (rki.de) | Trinkwasserverordnung / German Drinking Water Ordinance (bundesgesundheitsministerium.de) | Umweltbundesamt — Legionella in Drinking Water | GBA Group — German Drinking Water Ordinance and Legionella Testing | Gesundheitsamt Bremen — FAQ Legionella in Drinking Water