Rainwater Harvesting Systems details
What a complete rainwater harvesting system includes
A rainwater harvesting system collects runoff from a suitable roof or hard surface, removes debris, stores the water and distributes it to approved non-potable outlets. A complete installation may include leaf guards, pre-tank filtration, calming inlets, an overflow, a storage tank, level controls, a pump or booster set, a mains backup arrangement and dedicated distribution pipework.
The components must be designed as one system. A tank without enough catchment will rarely refill; a large catchment with inadequate overflow can create drainage problems; and an incorrectly selected pump may not provide the required flow or pressure.
Rainwater harvesting for dry-weather resilience
Stored rainwater can reduce reliance on mains water for suitable uses when rainfall and demand are properly balanced. This is particularly useful for estates, gardens, farms, schools, workshops and commercial premises with regular irrigation, cleaning or toilet-flushing demand.
Storage is most effective when there is a predictable non-potable demand throughout the year. Where the main requirement is seasonal, the design should consider how often the tank is likely to refill, how the water will turn over and what happens during extended dry periods.
Domestic rainwater harvesting systems
Domestic installations can supply garden irrigation, external taps, toilet cisterns and washing machines where the plumbing and controls are designed for that purpose. Options range from straightforward garden storage and pumping to buried tanks with automatic controls and a dedicated supply into the property.
Retrofit work requires careful planning because the system must remain separate from drinking-water pipework. Access for the tank, excavation, service routes and future maintenance can determine whether an underground, above-ground or alternative arrangement is most practical.
Commercial and estate rainwater harvesting
Commercial systems may serve landscape irrigation, yard or vehicle wash-down, toilet flushing, process support or other suitable non-potable applications. AFS can assess single buildings, estates and multi-use sites where storage, pumps and controls must respond to changing demand.
For larger systems, design information may include roof and hardstanding areas, occupancy or process demand, existing drainage drawings, available plant space, electrical supply, proposed storage location and the required delivery pressure.
Tank location, filtration and overflow
The tank can be above ground, below ground or incorporated into a plant area depending on capacity, access, appearance, ground conditions and the intended use. The structure supporting the tank, maintenance access and the route for replacing pumps or controls later must be considered before installation.
Filtration helps prevent leaves, sediment and other debris reaching the tank. The overflow also needs a suitable destination and should be designed so that a full tank does not transfer the flood risk elsewhere.
Pumps, controls and mains backup
The pump is selected for the required flow, pressure, duty pattern and tank arrangement. Controls may include level monitoring, dry-run protection, pressure control, duty and standby operation or remote alarms for commercial sites.
Where a mains backup is required, it must be arranged to protect the drinking-water supply and prevent cross-connection. Dedicated non-potable outlets and pipework should be clearly identifiable and the proposed arrangement should be reviewed against the applicable water fittings requirements.
System sizing and design information
AFS will normally ask for the site address, proposed water uses, approximate daily or seasonal demand, catchment drawings or roof area, photographs, access information and any existing drainage or services plans. This allows the initial design to focus on storage that can realistically be filled and used.
For developments where the harvesting system also forms part of the surface-water strategy, runoff calculations, attenuation requirements and the wider drainage design may also be needed.
Installation, commissioning and maintenance
Installation can include excavation or tank positioning, inlet and overflow connections, filters, pump equipment, control panels, distribution pipework and electrical work within the agreed scope. Commissioning checks confirm that the system fills, controls respond correctly, the pump delivers the intended duty and outlets are clearly identified.
Routine maintenance should include accessible filters, tank condition, inlets, overflow, pumps, level controls and backup arrangements. For pump faults or an existing system that is not delivering water, see our rainwater harvesting pump repair and servicing page.
Request a rainwater harvesting survey
AFS supports rainwater harvesting projects within about 50 miles of Alton; for sites more than 40 miles away we will confirm whether we can attend. Send the site details and postcode, or call 01420 561661, to discuss a new system, retrofit or upgrade.
