Rainwater harvesting is the process of collecting and storing precipitation that falls onto prepared surfaces, typically a home’s roof. This practice allows homeowners to reduce reliance on municipal water sources, conserve local water supplies, and gain water independence. Setting up a safe and effective system requires careful planning regarding collection surfaces, the storage vessel, and purification steps. This guide provides an overview of the components and procedures necessary to ensure the collected water is of high quality for home use.
Choosing the Right Storage Container
The primary decision in setting up a rainwater collection system is selecting the container material and size, both of which affect water quality and usability. For residential applications, tanks made from food-grade polyethylene plastic are a popular choice due to their affordability, corrosion resistance, and light weight. Alternative materials like stainless steel or concrete are also excellent options for long-term storage; stainless steel offers superior purity, and concrete provides durability and thermal insulation.
The tank must be completely opaque to block sunlight penetration. Preventing light from reaching the water inside the tank is the simplest method for inhibiting biological growth, as algae rely on photosynthesis. Proper sizing is necessary, which involves calculating the collection potential of the roof area against local rainfall patterns.
A simple estimation suggests that every square meter of roof space can collect approximately one liter of water for each millimeter of rainfall. Homeowners should compare this potential collection volume with their intended water usage. Final tank placement requires a stable, level foundation to support the weight of stored water, and the location should be close to the downspout connection for efficient plumbing.
Pre-Storage Filtration Systems
Maintaining water quality begins through a series of physical filtration steps before the water enters the main storage tank. The first defense involves installing leaf screens or debris catchment baskets at the gutter or downspout level. These devices prevent large organic matter like leaves, twigs, and bird droppings from entering the system, which can decompose and introduce contaminants into the stored water.
A highly recommended component is the first-flush diverter, designed to discard the initial, dirtiest flow of water from the roof. During dry periods, dust, pollen, and accumulated contaminants settle on the roof surface, and the first rainfall washes these materials away. The diverter intercepts this initial volume of water, preventing it from mixing with the cleaner water that follows.
These diverters often consist of a dedicated vertical pipe chamber that fills with the initial runoff. Once this chamber is full, a floating ball rises and creates a seal, diverting the subsequent, cleaner flow of water past the chamber and into the storage tank. This mechanism significantly reduces sediment and microbial contamination, such as fecal bacteria, that enters the main storage volume.
The diverted water slowly drains out through a small weep hole at the bottom, allowing the system to automatically reset itself for the next rain event. Fine-mesh screens should be placed directly before the water inlet on the tank to catch any remaining small particles. Implementing these three filtration steps—screens, first-flush diverters, and fine-mesh inlet filters—is an effective strategy for ensuring the water entering the tank is as clean as possible.
Securing and Maintaining Stored Water
Once the collection system is installed, ongoing maintenance is necessary to secure water quality and the integrity of the tank. The tank’s access points, including the lid and inlet, must be tightly sealed. This prevents light entry and stops pests like insects and small animals from contaminating the supply. A sealed system also eliminates standing water access points, which is the most effective way to prevent mosquito breeding.
Consistent water usage is a simple method to prevent water stagnation and the growth of algae or biofilm inside the tank. Water should be drawn off and replenished regularly to cycle the volume, which helps maintain freshness. Even with an opaque tank, shading the storage container is beneficial, as reduced temperature fluctuations also inhibit microbial growth.
A routine maintenance schedule should include checking all screens and filters for clogs, especially after heavy rainfall events. Homeowners should also inspect the tank’s lid and pipe connections for cracks or leaks. Periodically, the tank interior will require cleaning to remove the accumulated layer of fine sediment and sludge at the bottom. This is best accomplished by draining the tank and gently scrubbing the interior surfaces.