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Communal Rainwater Harvesting Versus Individual House Systems

Quick explanation

  1. Rainwater is collected from the roof of each home.
  2. Preliminary filtration removes large debris (like leaves).
  3. Rainwater enters the main storage tank via an inlet calmer.
  4. Sedimentation allows sediment to settle on the base of the tank.
  5. Rainwater is pumped from the tank via a floating suction hose.
  6. Rainwater is transported to multiple header tanks throughout the development.
  7. Rainwater is boosted to each home for non-potable use.

Detailed explanation


Rainwater is collected from the roof area of each home and transported via separate pipework. Separate pipework will prevent the cross-contamination of the roof water and surface water runoff.

Roof rainwater and surface water runoff are always kept separate as only roof rainwater will be reused. Surface water contains additional contaminants which are not suitable for reuse in most instances.  

Roof rainwater is transported to a central location on the development.


Leaves and undissolved particles are separated before the main storage tank via a pre-tank filter. Pre-tank filters trap any debris above 1mm on a mesh surface, allowing clear rainwater to flow into the tank.

Stormsaver pre-tank filters are designed to be fully removable from ground level for maintenance purposes. Stormsaver Systems integrates the pre-tank filter within a separate chamber in the main storage tank for ease of installation.


After preliminary filtration, rainwater enters the main storage tank via a calmed inlet.

The calmed inlet prevents the disturbance of fine sediment in the base of the storage tank. Rainwater Harvesting tanks are designed to naturally overflow (around three times per year if not reused) to prevent stagnation.

Submersible pumps sit within the storage tank and draw water from the cleanest part of the storage tank via a floating suction filter.

Rainwater tanks can also be connected to attenuation capacity via Active Attenuation. Learn more here.

Additional filtration

Best practice specifications will include an optional third stage of filtration to protect the system against smaller debris. Stormsaver provides Automatic Backwash Filtration to achieve a self-cleaning solution for third-stage filtration. Learn more here.

Secondary storage

Rainwater is boosted from a central storage tank to smaller header tanks around the development. The number of header tanks is determined by the location and number of homes served by the rainwater harvesting system.

Mains water top up

An intelligent mains water top up is achieved in the header tank via a WRAS-compliant air gap.

Stormsaver Systems are supplied with mains water protection in the form of a mechanical shut off valve. This vital feature protects against waste in the event of a solenoid valve failure.

Did you know that many regions in England are considered ‘seriously water stressed’ by the Environment Agency? As the country's future water deficit grows to an additional 5 billion litres per day by 2050, communal rainwater harvesting offers a long-lasting solution to improve water efficiency within homes.

Issues around water scarcity are not the only problem with water in the UK. Water management is also an issue with aging sewage infrastructure regularly reaching capacity and releasing pollutants into nearby natural water courses.

Rainwater harvesting is a solution to both of these problems. Not only can systems reduce per capita consumption of water by replacing precious drinking water with recycled rainwater in non-potable outlets, but rainwater harvesting also prevents large volumes of surface water from entering the over-capacity drainage network.

Rainwater harvesting is proven to reduce water consumption in residential properties by up to 55%.

Our Communal System Types

Communal rainwater harvesting can be achieved through a variety of different system types. The best type of system for your development is determined by the size, number of homes, and water demand requirements.

Our experts can advise on the best solution for achieving optimal water savings and minimising stormwater discharge rates. See a summary below.

 Community rainwater harvesting diagram showing rainwater being captured from roof areas and recycled.

Non Pressurised System

  • Provides high flow rates for use points.
  • Suited for medium to large developments, more than 10 homes.
  • Compatible with on-site attenuation systems.
  • Secondary header tank sized by number of homes.
  • Rainwater boosted from header tank via a booster set.  
  • Smart controls top up with mains water when rainwater is low.
  • Above ground components housed in brick or GRP buildings, not in homes.
  • Reliable water supply in failure and maintenance scenarios.

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 A rainwater harvesting diagram showing a storage tank and control unit

Combi System

  • Simple to install solution providing high flow rates.
  • Ideal for medium-sized apartment blocks or small-scale developments.
  • Includes a secondary break tank within the combi control unit for internal capacity.
  • Combi control unit supplied in 225, 400, and 620-litre capacities.
  • Positioned in a plant room or weather-proof cabinet.
  • Pre-wired, pre-built, pre-tested unit with an energy-efficient booster set.
  • Automatic mains water top-up via a compliant air gap.

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Technical Features 

PLC Controls: Smart system with easy-to-replace components, minimising downtime compared to more common PCB controllers.

Intelligent Systems: Centralised control panel ensures stability, easy monitoring, and minimal water supply disruption.

BMS Connectivity: Custom-designed to easily monitor storage levels, water consumption, faults, salinity levels, and temperature.

Mains Water Backup: Always prioritises rainwater but will automatically switch to mains water when necessary for a steady supply.

Mains Water Protection: Prevents mains water wastage with automatic shutoff valves and alerts, avoiding high water bills in valve failure scenarios.

Header Tank Optimisation: Smart controller ensures the header tank is always full, ensuring the system can keep up with demand.

Multi-Tank Compatibility: Works with multiple header tanks, reducing the need for multiple systems on large projects.

Further Information

  • Remove ownership and maintenance responsibilities from the homeowner to a management organisation.
  • Remove internal components from homes, assisting with reduced risk of cross-contamination between the rainwater and mains water supplies.
  • Prevent homeowners from switching the system off due to a lack of knowledge.
  • Can be linked with onsite attenuation capacity for a more cost-effective per-dwelling solution.
  • Can work as part of a wider biodiversity plan whilst saving space by reducing the required capacity of swales and ponds.
  • Utilise commercial grade components for extended lifespan.
  • A single point of maintenance.
  • Mitigate the need for consumer behaviour changes in water usage by supplying them with rainwater.

Many rely on the ‘water fittings’ approach for achieving greater water efficiency within homes. Water fittings are technologies that reduce the use of water in key outlets, examples include air-assisted showers, aerated toilet flushing, and dual-flush toilets. Communal rainwater harvesting is the optimal water-saving solution because…

  • Communal systems cannot be simply removed by homeowners for high water using alternatives.
  • Using rainwater rather than mains water is commonly seen as indistinguishable.
  • A lasting piece of infrastructure which can be monitored, maintained, and enforced.
  • Offers centralised monitoring of water levels and water savings.

Why Choose Stormsaver?

Our Added Value Options

Looking for additional filtration, UV disinfection, or installation services? Our added value options give you access to best-practice approaches. Learn more here. 

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Constructionline Gold Member CHAS Accredited UK Rainwater Harvesting Association Member Safecontractor Approved Waterwise Affiliate UK Business Awards Winner 2022