Heavy rain in 2026: Prevent backwater, keep cellars dry

2026 is a year in which many people only think about their wastewater pipes when it's already too late: it rains briefly but heavily. And suddenly there's a gurgle in the sink, the floor drain in the cellar smells bad - or the water is already standing in the laundry room.

The good news is that backwater and flooding can be avoided in many cases. Not with magic, but with a few clean routines, the right checks and, if necessary, professional precautions.

If you are already in the middle of a problem: 24-hour emergency service or to the overview of services on kanalhelden.ch.

What is backwater - and why does it hit the basement first?

In simple terms, backwater means that the wastewater can no longer drain away normally. During heavy rainfall, the sewer system is heavily loaded. If a pipe in the house is also partially blocked, there is no backflow protection or a drain in the cellar is the lowest point, the water seeks the path of least resistance - and unfortunately this is often the floor drain in the cellar.

Typical warning signs that are still underestimated in 2026:

•   Gurgling in WC/sink as soon as it rains heavily outside
•   Water drains slowly in shower/sink
•   Unusual odor from the drain (even temporarily)
•   Basement drain looks damp, although no one has used water

If you are in the city of Zurich: At the first signs, professional clarification is often cheaper than the water damage afterwards. Find out more: Sewer cleaning Zurich.

10-minute emergency plan if it is already backing up

If water is pushing up or the situation is tipping over, these steps will help (without panic, but quickly):

1. Do not run any more water (do not flush, do not shower, do not start the washing machine).
2. Check electricity in the affected area (water and sockets are a bad combination).
3. Put up valuables; provide towels, bucket, wet vacuum cleaner (if available).
4. Observe cellar drains and lowest points: Is water coming up? How fast?
5. Organize help immediately if things escalate - especially at night or at the weekend.

For such cases: 24-hour emergency service. And if it's more of a plumbing emergency (e.g. burst pipe/water damage): Sanitary emergency Zurich or Sanitary emergency.

Preventing a backlog: The 2026 checklist

A) For homeowners (single-family house / condominium)

Can be implemented immediately (today or this week):

•   Keep floor drains in the cellar clear: do not store anything above them (boxes, mats, shelves directly on the floor).
•   Visual check of all drains: does it smell strong, is it gurgling, is it damp?
•   Check rainwater drains: Balcony drain, light well, garage ramp, yard drains.

Monthly (5 minutes, honest):

•   Gullies/manhole covers around the house: remove leaves, gravel, dirt.
•   In heavy rain, take a quick look to see if there are any puddles (this is an indication).

1-2× per year (as a preventive measure, before things go wrong):

•   Have the condition of the pipes checked (e.g. with a camera/TV inspection) and clean if necessary.
•   Especially if there have been problems before: better before than again.

If you want to take a clean approach: Free preventive check-up.

B) For administration (apartment buildings, commercial, underground parking)

Administrations need one thing above all in 2026: a plan that is not just written in the event of a claim.

Documents & Routine:

•   Wiring diagram/revision openings: Where are they? Who has the keys?
•   Protocol: When was the last cleaning/inspection, what were the findings?
•   Tenant sensitization: Wet wipes do not belong in the toilet (yes, annoying - but saves trouble).

Technology & risk:

•   Identify critical zones: Underground garage, plant room, laundry room (lowest points).
•   Take recurring faults seriously: „It was almost twice...“ is actually an alarm.
•   In the event of damage: not only clean, but also clarify the cause (subsidence, roots, cracks).

Partner & Accessibility:

•   Emergency contact clear: Who responds at night/weekends?
•   Regional deployment planning: useful for several properties.

Helpful for the overview: Our locations in Switzerland.

Case study 1: Basement in Zurich district 3 - why it happened (before/after)

Initial situation (before)

An apartment building in Zurich district 3, downstairs: Laundry room, cellar compartments, a floor drain in the middle of the room. There were small signs for months: When it rained heavily, there was a brief gurgle. Once it smelled like a sewer in the cellar, then it was quiet again. And the laundry room was just slightly damp - but nobody wanted to open the barrel.

What happened next

On an evening of heavy rain, water pushes into the drain. A little at first - then suddenly a lot. Cardboard boxes in a cellar compartment soak up, the smell remains. It is then crucial not only to „flush freely“, but to proceed in a structured manner:

•   Acute relief (so that it does not push up any further)
•   Cleaning (high pressure/suction depending on the situation)
•   Find the cause (camera/TV inspection instead of „just rinse and hope“)

Zurich is a good place to start: Sewer cleaning Zurich.

Result (After)

•   Drain runs freely again, no more gurgling.
•   The administration defines a maintenance rhythm (instead of „we'll let you know when it stinks again“).
•   Cellar drains are cleared: no boxes directly on the floor, clear view of critical points.
•   And very importantly, you reduce the risk of the next thunderstorm - not just the symptoms.

Practical case 2: Lucerne - underground parking garage, ramp, courtyard drainage

In Lucerne, a frequent trigger is not even the toilet, but the combination of a garage ramp, heavy rainfall and a yard drain that is partially blocked. The water then stands on the ramp, runs off via the lowest point and, in the worst case, finds its way towards the building.

Find out more regionally: Sewer cleaning Lucerne.

Case study 3: Winterthur - „It's never an emergency until it is“

Over a period of two years, an administrative office in Winterthur repeatedly had minor faults: sometimes a toilet on the ground floor, sometimes a drain in the stairwell. Nobody wanted to „spend money unnecessarily“. In 2026, there was one evening when two parties called at the same time: The toilet was overflowing and there was a strong smell in the basement.

A clear process makes the difference: contact, on-site appointment, cleaning, report, maintenance plan.

Regional entry: drain cleaning Winterthur.

Practical case 4: Basel (Grossbasel) - Backwater in the laundry room after heavy rainfall

Place & object Apartment building from the 60s in Grossbasel. Basement with laundry room, cellar compartments and floor drain (lowest point).

Initial situation (Before): There were warning signs, but nothing that seemed „urgent“:

•   Gurgling in the floor drain after periods of heavy rain.
•   Temporary unpleasant odor in the basement, especially after weekends.
•   Yard inlet outside quickly becomes clogged with leaves.

The trigger (heavy rain): A short, heavy thunderstorm. Within minutes, water pushes up from the floor drain. Two cellar compartments are affected, cardboard immediately becomes a sponge.

What typically happens on site (operational logic):

1. Acute relief: Stop water consumption, secure affected area, vacuum if necessary.
2. Clear the pipe/channel: High-pressure flushing and suction until the flow is stable.
3. Narrow down the cause: Constriction due to deposits/foreign bodies (TV inspection if necessary).
4. Brief report to administration/janitor: findings + clear recommendation for prevention.

Why it happened: Not just the rain. A partially constricted pipe plus a yard inlet that doesn't swallow enough during heavy rain - and the cellar drain becomes a weak point.

Result (After): After cleaning, everything runs smoothly again. The administration includes the courtyard inlet, cellar drains and main pipe in a simple maintenance schedule - so that not every storm becomes a risk in 2026.

You can find out more about our services here at Sewer cleaning Basel.

Practical case 5: Bern (Marzili) - Backwater in the ground floor WC and damp cellar

Place & object: Old building with two apartments and a small studio on the ground floor, near Marzili. Basement with floor drain as lowest point.

Initial situation (Before): There were „mini-problems“ for weeks:

•   WC on the ground floor sometimes flushes slowly and gurgles.
•   Shower occasionally runs more slowly.
•   Odor in the cellar comes and goes.

The moment it tips over: Heavy rain outside, at the same time water is being used in the house. Suddenly the toilet on the ground floor overflows, shortly afterwards moisture appears in the floor drain in the basement - classic backwater. A familiar case for us in the Pipe cleaning Bern.

As experience shows (typical for Bern): It is often a bottleneck caused by deposits (grease/soap residue) or an old transition in the pipe. During heavy rainfall, the reserve is then missing and the pressure pushes upwards.

Measures that really help:

•   Immediately stop running water (do not flush) until the pipe has been drained.
•   Clean the line specifically (not just „flush briefly“) so that deposits are removed.
•   In case of repetition: Schedule a TV inspection to rule out cracks / displacement / ingrowth.
•   Prevention: Define maintenance and briefly inform residents what does not belong in the toilet.

Result (After): The toilet works normally again, the cellar remains dry. The decisive step is the plan afterwards: Fix the bottleneck, set the rhythm, done.

When it's not just cleaning: damage to the sewer and pipe

Sometimes the pipe is not only dirty, but also damaged (often cracked, leaking, settling). In this case, cleaning is sufficient in the short term, but the issue will return. In such cases, it is worth taking a look at:

•   Sewer renovation
•   Inliner renovation

Common 2026 mistakes that you can avoid

•   „Chemicals in, problem gone“: it often only postpones the problem or makes it worse.
•   „Ignore “just a little gurgle": This is often the last warning signal before the big night.
•   Wet wipes and the like: banal, but real - and often the cause in apartment buildings.

Matching background article: Clogged toilet - causes, help & responsibility.