Using rainwater as process water on the construction site conserves resources, reduces logistics effort, and lowers environmental impacts. Especially in concrete demolition and special deconstruction, in building gutting and cutting, as well as in rock excavation and tunnel construction, there is a high demand for service water—for example for dust suppression, wet cutting, cleaning, or surface moistening. In work areas where Darda GmbH hydraulic demolition tools such as concrete demolition shears or rock and concrete splitting devices are used, captured rainwater can be a robust, practical source for these tasks—properly treated and safely supplied.
Definition: What is meant by rainwater harvesting on the construction site
“Rainwater harvesting on the construction site” refers to the collection, storage, treatment, and demand-based provision of precipitation water directly at the place of use as non-potable water. This service water typically serves dust suppression, wet cutting and drilling, tool and surface cleaning, site moistening, as well as interim storage for process purposes. Drinking water standards are not targeted; instead, fit-for-purpose quality for technical applications is prioritized—while complying with occupational safety and environmental protection requirements.
Benefits and objectives of rainwater harvesting on the construction site
Rainwater harvesting supports construction and deconstruction projects by providing dependable service water directly on site. This improves dust control, stabilizes workflows, and reduces transport.
- Resource conservation: Reduced consumption of drinking water for technical purposes.
- Dust suppression: Effective binding of mineral dust during demolition, crushing, and cutting operations.
- Logistics: Fewer water deliveries, greater independence at remote sites.
- Environment: Lower discharges of uncontrolled runoff; better retention and sedimentation of solids.
- Process reliability: Demand-based availability for wet cutting, cooling, cleaning, and moistening.
Demand and typical applications in demolition and deconstruction
Water demand depends on methods, daily output, weather, and dust limit values. In Darda GmbH’s fields of application, the following focal points arise:
Concrete demolition and special demolition
During demolition with concrete demolition shears, combination shears, or during secondary breakage of components, fine concrete dust is generated. Rainwater is suitable for perimeter wetting and targeted dust binding in the work area, for example via spray lances or nozzles. For cleaning exposed reinforcing steel or flushing work surfaces, simple sedimentation before reuse is sensible, as fine concrete dust can increase pH.
Building gutting and cutting
In wet cutting and drilling (e.g., separation cuts, core drilling), rainwater serves as a cooling and flushing medium. It is important to remove slurries (cement fines) before recirculation or disposal. Two-stage treatment—sedimentation and filtration—improves usability and protects pumps and nozzles.
Rock excavation and tunnel construction
In underground or spatially confined areas, dust control is particularly important. Moistened work surfaces and fine but controlled spray patterns reduce aerosol exposure and visual impairment. Rainwater reserves provide operational security where external supply is limited.
Natural stone extraction
During splitting, sawing, and sorting of natural stone, captured precipitation water supports dust binding, cools cut edges, and facilitates cleaning. Water quality should be low in particles to protect nozzles and valves in continuous operation.
Special deployments
In temporary or remote operations—for example, in emergency stabilizations or partial demolitions—mobile rainwater provision enables rapid, self-sufficient dust suppression without waiting times for external water supply.
Planning and sizing: From area analysis to operation
A structured approach ensures that storage volume, delivery capacity, and treatment match the task.
- Demand analysis: Which processes require service water (dust suppression, wet cutting, cleaning)? What peak withdrawals are expected?
- Yield estimation: Which areas provide precipitation water (roofs, canopies, tarps)? How is rainfall distributed seasonally?
- Storage concept: Size and type of storage (IBCs, mobile cisterns, retention containers) including reserve for dry spells.
- Treatment: Sedimentation, screening/filtration, if necessary turbidity monitoring; for concrete-laden water, pH control according to general, conservative guidelines.
- Distribution: Pump capacity, hose runs, couplings, shut-off, marking “Not drinking water”.
- Operation: Inspection intervals, cleaning routines, documentation of volumes and quality.
Mass balance – simple estimation
A practical estimate results from effective collection area, regional precipitation, and an efficiency factor (losses due to evaporation, overflows, filters). Example: If a covered area of 200 m² receives a rainfall event of 10 mm with an efficiency of 0.8, around 1,600 liters are available. Multiple events per week add up to the usable reserve, provided sufficient storage is available.
Typical consumption values (guidance ranges, non-binding)
- Dust suppression in the demolition area: approximately 2–10 l/min per spray nozzle, depending on spray pattern and wind.
- Wet cutting/wet drilling: approximately 5–15 l/min per saw or drill bit, depending on diameter and material.
- Cleaning of work surfaces/tools: depending on the method, 200–500 l per work section.
Guidance values do not replace project-specific determination; actual demands vary with material, equipment fleet, and daily output.
Technology: Collection, storage, treatment, distribution
Collection
- Sources: Hall and container roofs, material tents, temporary tarps, watertight channels.
- Pre-separation: Leaf traps, coarse screens, and a stilling section to avoid resuspension of sediments.
- Separation: No inflow from areas with oil or hazardous substances; separate collection prevents mixing.
Storage
- Storage types: IBC containers, mobile cisterns, open or covered retention tanks.
- Operation: Cover to prevent ingress, protection against algae growth, frost-proof setup, stable storage.
- Safety: Emergency overflow, backflow prevention, clearly marked fill and draw-off points.
Treatment
- Sedimentation: Settling tanks or cascades to retain solids upstream of the pump.
- Filtration: Screen or bag filters (e.g., 100–300 µm) to protect nozzles and pumps; fine filtration if needed.
- pH management: Fine concrete dust can make the water alkaline; apply cautious, general neutralization measures and route discharge according to the responsible authority’s requirements.
- Oil separation: Provide a downstream separator where potential oil ingress is possible.
Distribution
- Delivery: Matching pump capacity and pressure for spray nozzles and hose lengths; dry-run protection.
- Lines: Robust hoses, suitable couplings, shut-off valves, non-return (backflow) preventers.
- Marking: “Not drinking water” at all draw-off points; color-coded hoses help avoid confusion.
Water quality, occupational safety, and hygiene
Rainwater on construction sites is non-potable water and is used as process water. Regular visual checks (turbidity, odor), removal of sediments, and filter replacement increase operational safety. To avoid unnecessary aerosol formation, spray patterns should be designed for dust binding rather than fine mist. Personal protective equipment and skin-friendly work practices must be observed.
Legal and organizational aspects
In general: Discharging treated water into sewers, soil, or water bodies requires compliance with local authority requirements. These concern in particular solids content, potential alkaline reactions from concrete fines, and possible oil or contaminant inputs. Early coordination with responsible bodies, clean separation of water streams, and transparent documentation of volumes and disposal routes are recommended. Statements herein are always non-binding and do not replace official guidance.
Integration into the use of Darda GmbH hydraulic tools
Concrete demolition shears
When crushing concrete components, dust forms along break and tear edges. Rainwater can be applied via short-throw nozzles in the effective zone. Robust filtration stages are advantageous to keep nozzles clear, along with a spray pattern that binds dust without creating puddles.
Rock and concrete splitting devices
These hydraulic rock and concrete splitters operate with low vibration. Supplemental surface moistening reduces dust generation during set-up and follow-up work (e.g., with additional separation cuts). Rainwater is suitable for this if provided with low particle load.
Other cutting and shear tools
For combination shears, multi cutters, steel shears, or tank cutters, rainwater is primarily used for dust suppression in the vicinity, for surface cleaning, and for cooling auxiliary cuts. Safe provision via clearly marked, unmistakable lines is essential.
Operation, monitoring, and documentation
- Inspection: Regularly check storage, screens, filters, and hose connections.
- Cleaning: Remove sediments in a controlled manner and dispose of them properly.
- Monitoring: Record simple key figures such as liters withdrawn per day, rainfall amounts, and filter change intervals.
- Winter operation: Provide a freeze protection concept (draining, insulating, heated components).
- Emergency: Define overflow paths and emergency shut-offs.
Avoid common mistakes – proven practical solutions
- Storage too small: Plan a safety margin for low-rain periods.
- No pre-screening: Combine coarse and fine separation to protect pumps and nozzles.
- Mixing with contaminated water: Strict separation by origin and quality.
- Missing labeling: Clearly mark all draw-off points as non-potable water.
- Insufficient pH attention: Check concrete water for alkaline reaction and treat according to requirements.
Step-by-step implementation in practice
- Define demand and plan draw-off points (dust suppression, wet cutting, cleaning).
- Specify collection areas, provide pre-cleaning, and determine storage size.
- Configure treatment (sedimentation, staged filtration, pH control if needed).
- Design distribution paths and pump capacity for nozzle technology and line lengths.
- Implement labeling, training, and an inspection plan.
- Monitor operation, keep documentation, and iteratively adapt the system.