Rainwater harvesting in the Swiss garden: sustainable and cost-saving

Rainwater harvesting in Swiss gardens combines practical sustainability with tangible cost benefits. In many communities, drinking water consumption for watering gardens during the summer droughts is a challenge - also financially. Collecting rainwater reduces the burden on the public water supply, conserves resources and supplies beds, lawns and hedges with soft water that plants have proven to tolerate well. With the right system - from a simple rain barrel to an underground cistern - rainwater harvesting can be planned and operated safely depending on the size of the property and roof area.

Why is it worth using rainwater in Swiss gardens?

Rainwater harvesting reduces drinking water consumption, especially in gardens with lawns, flower beds and privacy hedges. Soft rainwater prevents limescale deposits on plants and irrigation technology, which increases the service life of drip hoses and micro-sprinklers. At the same time, a rainwater storage tank reduces runoff peaks during heavy rainfall events: The property can retain water instead of discharging it directly into the sewer system - in many places a plus point in residential areas with a high level of sealing.

Typical areas of application in family gardens

In home gardens with play areas, vegetable patches and herbaceous borders, rainwater is used for watering, drip irrigation, pond replenishment or cleaning garden furniture. If there is sufficient volume, rainwater harvesting can also be considered for toilet flushing or washing machines - however, this requires clear separation from the drinking water network, reliable replenishment, correct labeling and professional installation in accordance with local regulations.

Which systems are suitable - from rain barrel to cistern?

The right solution depends on the roof area, garden requirements, available space and budget. Starting small and expanding later is no problem. The following overview shows common systems with typical applications and approximate costs.

Important components for reliable rainwater harvesting

• Filter and leaf trap: retain coarse material; clean regularly.
• Steady inlet and floating drainage: reduce sediment turbulence and ensure clear drainage water.
• Overflow with backflow flap: prevents backflow from the sewer system; ideal for coupling with infiltration basin.
• Pump/pressure control: provide constant pressure for hose or irrigation system; combine with drinking water feed and separation system for domestic use.
• Level indicator and overflow edge: facilitate management during periods of heavy rainfall.

How much rainwater can be collected? Practical example calculations

The annual volume depends on the roof area, regional precipitation and runoff coefficient. A simple approximation: collected volume (m³) ≈ roof area (m²) × annual precipitation (m) × runoff coefficient (approx. 0.8). For example, a roof area of 100 m² with approx. 800 mm of precipitation per year and a runoff coefficient of 0.8 approx. 64 m³, i.e. around 64,000 liters.

Note: Rainfall varies considerably from region to region (Alps/Midlands/Jura). For gardens with a large watering requirement, it is worth having a cistern that can bridge several weeks of low rainfall. For flower beds and smaller lawns, linked rainwater barrels or a compact above-ground rainwater storage tank are often sufficient.

Planning and approval in Switzerland: What needs to be considered at property and municipal level?

Cantonal and municipal regulations play a key role in implementation. Underground cisterns, earthworks, distances to property boundaries and discharges into sewers or infiltration troughs may require notification or approval. In some municipalities, retention and infiltration solutions are desirable, sometimes with an impact on fees. Consultation with the local authority at an early stage makes planning easier and saves costs later on.

Site selection, roof surface and material compatibility

• Inflow as far as possible Place close to the gutter, short pipe runs reduce losses.
• Pay attention to the roof material: Water running off copper surfaces or bitumen sheets may contain substances that are undesirable for the consumption of sensitive leafy vegetables; it is generally less critical for soil irrigation.
• Take statics and frost depth into account (underground pipes at frost-free depth, observe local values).
• Manage overflow sensibly: Infiltration on your own property, retention boxes or - where permitted - regulated connection to the rainwater pipe.

Safety in the family garden: childproof rainwater harvesting

• Always equip rainwater barrels and shafts with childproof, lockable lids.
• Use fine-meshed grids/nets against mosquitoes; avoid standing water without a cover.
• Minimize non-slip installation, fixed hose routing and tripping hazards.
• Never use rainwater as drinking water; clearly mark pipes, exclude cross-connections.

Irrigation solutions: How can rainwater be used as efficiently as possible?

Efficiency determines how long stored rainwater lasts. Drip irrigation targets water to the roots, reduces evaporation and keeps leaves dry - ideal for berries, vegetable patches or hedges. A simple irrigation computer with a moisture or rain pause sensor prevents unnecessary running times. Mulching with grass clippings or wood chippings preserves soil moisture and stabilizes the microclimate. Water in the morning during hot spells to minimize losses.

Winter operation and maintenance

• Empty above-ground containers before frost or set up frost-proof; leave the tap open to avoid tension.
• Clean filter units, maintain pumps and controls according to manufacturer's instructions.
• Underground cisterns usually only require an annual visual inspection; remove sediment if necessary.
• Flush drip lines and valves, check seals, observe frost protection.

Costs, savings and amortization - realistically estimated

The investment varies greatly with volume, installation and technology. The following components are relevant for a rough guide. Prices are approximate and vary depending on the provider, region and building conditions.

Depending on the water price, charges and consumption, a medium-sized rainwater harvesting system can pay for itself over the years. The effect is particularly noticeable during long dry spells when a lot of watering takes place. If the overflow is directed into an infiltration system, there may be additional benefits depending on the municipality (e.g. less wastewater pollution; information not guaranteed).

Step-by-step: How to create a robust rainwater harvesting system

1. 1 Clarify requirements: Assess garden area, plant types, watering habits and possible house use.
2. 2 Record roof areas and estimate potential yield; select suitable downpipes.
3. 3 Select a system: Couple rain barrels or plan cistern; check location, excavation and pipe routes.
4. 4 Involve the municipality/canton: Clarify reporting or authorization requirements, drainage concept, infiltration.
5. 5 Define components: Filter, calmed inlet, overflow with backflow flap, pump, drip irrigation.
6. 6 Have the system professionally installed or - in the case of simple systems - install it carefully yourself.
7. 7 Optimize operation: Determine watering times, mulch coverage, sensors and maintenance intervals.