Rainwater lends itself well for reuse due to being clean and clear when it falls from the sky. This means that relatively little filtration is required to make it safe for a non-potable water supply.

Rainwater is collected via the roof drainage points and into a central storage tank. Rainwater from the roof area is of the highest quality and does not contain any contaminants or pollution from vehicles, unlike rainwater collected from hard-standing surfaces.

Before entering the storage tank, rainwater passes through a pre-tank filter to remove leaf and roof debris. The pre-tank filter is rated at 1000 microns (1mm).

Rainwater enters the storage tank via a calmed inlet to prevent the disturbance of fine sediment on the base of the storage tank.

On retrofitted systems, storage tanks will be located as close to the roof drainage points as possible to minimise pipework alteration requirements.

Rainwater is then collected from the cleanest part of the storage tank via a floating suction filter and drawn through a set of submersible pumps (or a booster set on the StormStation).

An intelligent mains water top-up will operate automatically via a solenoid valve during dry spells or when there are limited rainwater supplies available. This mains water top-up is physically separated from the public water supply via a compliant air gap to prevent cross-contamination.

An option third stage of filtration can be achieved via automatic backwash filters which remove small particles to improve the quality of the rainwater supply. Learn more about this technology here.

Rainwater is then distributed to points of use around the building.

There has never been a more crucial time to consider retrofitting a rainwater harvesting system. Climate change and population growth are causing significant challenges for our water supplies. In the drier months, water scarcity is prevalent, and in the wetter months, national drainage infrastructure cannot cope with excess stormwater.

Within the last two decades, there have been many advancements in water-saving technologies, one of which is rainwater harvesting. These valuable water-saving systems can provide significant water savings by capturing rainwater from the previously underutilised roof area of a building.

Rainwater Harvesting can provide your existing building with a non-potable water management strategy, in line with your sustainability goals.

Recycled rainwater is an alternative to using precious drinking water supplies for outlets including, toilet flushing, vehicle wash down, irrigation, manufacturing, cooling, and many other applications.

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Rainwater Harvesting can provide water savings of up to 75%. On retrofitted systems, savings are highly dependent on how much rainwater can be diverted away from the drain and into the rainwater harvesting storage tank.

We provide free-of-charge desktop surveys to provide potential water-saving estimates, potential costs, and runoff savings. We can then provide a full proposal based on an in-depth site visit.

Our site visits enable you access to a rainwater harvesting expert who will consider the drainage locations, potential tank sizing, and points of use locations.

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Our Retrofit System Types

Retrofit rainwater harvesting can be achieved through a variety of different system types. The type, scale, and water demand requirements of your building will determine which system is right for you.

Our experts will advise on the best solution for achieving higher water efficiency and meeting your sustainability goals. See our solutions below.

 rainwater harvesting diagram. The image shows a rainwater system which has been retrofitted to an existing site


  • The easiest solution to install on the market!
  • Above-ground unit, no excavation needed.
  • A plug-and-play system, including pumps, controls, filters, and storage all in one.
  • Can be supplied with solar panels for carbon neutral operation.
  • Available in sizes 3,000 to 20,000 litres, covering the most common tank capacities.
  • Features self-circulating UV disinfection to prevent bacteria growth.
  • Branded to bespoke specifications.
  • External placement near usage points and roof drainage areas.
  • Automatic mains water top up for when rainwater is low.

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 A small retrofit rainwater harvesting system diagram. The image shows the system working within the building to capture and recycle rainwater

StormStation Micro

  • Self-contained rainwater harvesting unit with a 1,000L tank.
  • Ideal for retrofitting small buildings like convenience stores and drive-thrus.
  • Can be installed inside a plant room or in a weatherproof enclosure.
  • Features intelligent mains water top-up.
  • Compact and easy to install.
  • Equipped with a self-circulating UV disinfection system to prevent bacteria.
  • Offers a pressurised rainwater supply via a variable speed booster set.

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 an above ground rainwater harvesting diagram.

Above Ground Systems

  • Above-ground solution for excavation-free installation.
  • ideal for high water consumers in large buildings, like manufacturing sites.
  • Available in various system arrangements tailored to site needs.
  • Features a central storage tank, control panel, and booster set for pressurised rainwater supply.
  • Controls housed internally or in weather-proof enclosures.
  • Smart mains water top up for when rainwater is low.
  • Easy installation for minimal disruption.

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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

  1. Tell us your roof area, water demand, and postcode and we will complete a free-of-charge desktop survey. This service provides you with early costs, savings estimates, and sizing details.
  2. Should you wish to explore rainwater harvesting further, one of our experts will attend your site to survey the building for roof drainage points, mains water connections, and points of use, and to determine where the equipment will be situated (chargeable at a small fee which is redeemable against a final order).
  3. Our estimating team will provide you with accurate supply and installation costs.
  4. Upon placing the order, you will receive details about our full installation process.
  5. Start reusing valuable rainwater, don’t forget to maintain your system!
  • UK manufactured by us! Most UK suppliers buy the same system made in Germany. For you, this means rapid access to replacement parts when components fail, unlike equivalents which take 14 weeks to be delivered from Germany!
  • Unrivalled experience. As a supplier and maintenance provider who has been in the water reuse sector for over 20 years, we know what works and what does not work so well. All of this knowledge feeds into our design to provide the most robust systems.
  • Our business is water reuse. That means we are solely committed to saving water through rainwater harvesting and greywater recycling.
  • Quality installs. Our systems provide high levels of quality and include many fail-safe features to protect your building from a complete supply failure. Many alternatives simply do not have these important fail-safe features!

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