How does a rainwater harvesting system work?

Through five key stages—collection, pretreatment, storage, purification, and reuse—natural rainfall is collected, stored after removing initial pollutants, and then pumped out for use when needed.

I. Summary of Core Principles
Through five key stages—collection, pretreatment, storage, purification, and reuse—natural rainfall is collected, stored after removing initial pollutants, and then pumped out for use when needed. Rainwater exceeding the storage capacity is discharged via overflow facilities, thereby achieving the resource utilization of rainwater while alleviating the drainage pressure on the municipal sewer system.
II. Detailed Step-by-Step Operating Principles
1. Rainwater Collection Phase (Siphon Collection Section)
Polymer protective drainage profiles (siphon drainage panels) are installed beneath the soil cover of green spaces or garage roof slabs. Rainwater seeps through the soil layer and is collected by the drainage panels;
Under the combined effect of gravity and the siphon effect, the water flows into Siphon Drainage Channel A. Using T-joints and cross-joints to form a mesh-like drainage network, rapid water conveyance is achieved with zero slope;
The collected rainwater is transported via HDPE drainage pipes to the pretreatment equipment; the drainage panels and their seams are sealed with polymer adhesives to prevent soil from entering the pipe network and causing blockages.
2. Initial Rainwater Pretreatment Stage
The initial rainwater at the start of a rainfall event washes over the ground surface, carrying large amounts of pollutants such as silt, fallen leaves, and dust.
Waste Interception Basket: Intercepts large floating debris such as leaves and plastic bags;
Initial Runoff Diverting Device: Automatically diverts this contaminated rainwater, preventing it from entering the storage tank;
The remaining, relatively clean rainwater flows into the downstream storage tank.
3. Rainwater Storage Phase
Filtered rainwater is conveyed to a storage tank assembled from PP rainwater collection modules.
The exterior of the storage tank is wrapped in an HDPE impermeable geomembrane, forming a sealed water storage space; the modules’ open-cell structure provides an exceptionally high effective storage capacity for long-term storage of collected rainwater.
Note: If designed as an infiltration retention tank without an impermeable geomembrane, rainwater can slowly seep into the ground to replenish groundwater.
4. Rainwater Reuse and Distribution Phase
When rainwater is needed, the rainwater lift pump activates to draw water from the storage tank;
after passing through advanced filtration and disinfection equipment (optional for high-standard applications), the water is distributed to points of use: landscape irrigation, road surface washing, and landscape water replenishment, among others.
5. Overflow Discharge Protection
In the event of extreme downpours, when the volume of stored rainwater exceeds the tank’s capacity, excess rainwater is automatically discharged into the municipal stormwater network via an overflow well, preventing overloading of the underground storage tank and water accumulation on the roof slab.
III. Complete Water Flow Path
Rainwater infiltration → Collection via polymer siphon drainage profiles → Siphon drainage channels + T- and cross-fittings for flow diversion → HDPE drainage pipes → Pollutant interception and initial flow diversion pretreatment → Storage in PP modular retention tanks → Pressurized conveyance via lift pumps → On-site reuse
Excess rainfall → Discharge via overflow well