10 June 2026

Rainwater treatment systems: a guide to choosing between storage and continuous flow systems

Proper management of stormwater runoff is essential for environmental protection and hydraulic safety in any industrial context. This type of system is critical not only for activities exposed to the risk of accidental hydrocarbon spills—where precise mitigation strategies and compliant systems are required—but also for treating rainwater that washes over potentially contaminated surfaces such as parking lots, industrial yards, or car washes.

At Di Camillo Serbatoi Srl, we know that choosing between a storage system and a continuous flow system is not just an engineering decision, but a guarantee of compliance that protects your company from fines and environmental damage.

Storage Systems: The Safety of Physical Separation

The storage (discontinuous) system is often the ideal solution for areas where the risk of light liquid pollution is high, such as fuel transfer zones.

The Hydraulic Process and the Retention Phase

Operation is based on a temporal separation principle:

• Bypass rainwater: A bypass manhole channels the initial first flush water directly into the storage tank. Once the tank is full, a shut-off device prevents further water from entering, diverting the “second flush” (considered clean) directly to the final discharge point.
• Sedimentation and flotation: The collected wastewater remains in the tank for a “retention” or “quieting” period (usually between 48 and 96 hours). During this time, sludge settles to the bottom and hydrocarbons rise to the surface, facilitating the downstream oil separator’s work and increasing the pollutant removal rate.
• Controlled treatment: Once the delay period has elapsed, a pump delivers the water at a constant flow rate toward the final treatment unit.

Continuous Flow Systems: Real-Time Efficiency

As an alternative, there are Continuous Flow Treatment Systems (IPC). These systems do not involve volumetric storage; instead, they treat the entire stormwater flow as it passes through the system.

• Flow-based design: Unlike storage systems that operate based on volumes, continuous systems are sized according to critical rainfall intensity and peak flow rates.
• Operational advantages: They can operate entirely by gravity, reducing the need for electromechanical components such as pumps or PLC control panels.
• Technical considerations: While effective, they require rigorous maintenance because, during severe storms, the hydraulic retention time is reduced, which can affect effluent water quality compared to a storage system.

The Technological Heart: Class I Oil Separators and Intrinsic Safety

Regardless of the configuration, the core unit is the light liquid separator, which must comply with UNI EN 858 standards. To ensure maximum performance, we always recommend Class I technology.

1. Coalescence Filtration: Thanks to specialized filters, oil micro-droplets aggregate into larger droplets, gaining the necessary buoyancy to rise to the surface and remain trapped.
2. Automatic Shut-off Float Valve: This is a critical safety device. In the event of a massive accidental spill, the float loses buoyancy in the fuel and drops, mechanically sealing the outlet. This transforms the system into a watertight containment basin, preventing any escape of pollutants.

The Di Camillo Serbatoi Srl Solution

A properly designed system not only protects you from legal risks and fines but also ensures the continuity of your operations even during the most intense weather events. Whether it is a storage system for maximum safety or a continuous flow system for maximum hydraulic efficiency, our team is ready to guide you toward the most reliable technical solution.

Want to make your company a model of efficiency and environmental safety?

Don’t wait for the next emergency. Contact us for a dedicated consultation and discover how our systems can make a difference for your business.