Both the AA Eco-Plus and AA Silentio collect rainwater from your roof, keep the underground tank reserved entirely for rainwater, and manage mains backup automatically. The Silentio adds a reversible flow filter, a water level reader, and an automatic filter jet wash cycle. If you want the system to monitor and maintain itself with minimal input, the Silentio is the step up worth considering.
When people compare GRAF UK’s AA rainwater harvesting systems, the most common question is straightforward: what is the difference between the AA Eco-Plus and AA Silentio, and which one is right for their project? Both systems share the same core architecture. Both keep mains water out of the underground tank entirely. And both supply toilets, washing machines, garden irrigation, and outdoor cleaning automatically from harvested rainwater. The differences sit in three additional features on the Silentio, and whether those features matter to you depends on how you want the system to perform day to day.
What does the AA Eco-Plus and AA Silentio have in common?
Before comparing the two, it helps to understand what both systems share, because the foundation is identical.
Both the AA Eco-Plus and AA Silentio use the same core AA architecture. Rainwater is collected from the roof, filtered before entering the underground tank, and stored ready for use. A multi-mounted pump supplies harvested rainwater on demand to toilets, washing machines, garden taps, and outdoor cleaning. A dual switch setup manages auto mode and the pumping unit automatically, with no manual intervention required from the occupant.
When the underground tank runs low, both systems detect the mains supply and switch over seamlessly, keeping the home constantly supplied. The critical point is that in both systems, mains water feeds into a separate integrated cistern inside the property rather than the underground tank. The underground tank stays reserved entirely for rainwater at all times.
Both systems are available in tanks from 1,500 to 7,500 litres, manufactured from 100% recycled plastic, with free UK mainland delivery included and a 15-year tank warranty as standard.
What does the AA Silentio include that the AA Eco-Plus does not?
The Silentio builds on the Eco-Plus with three additional features. Each one addresses a specific aspect of system performance and long-term maintenance.
Reversible flow filter for an additional level of filtration. The AA Eco-Plus uses GRAF’s high-performance inlet filter to remove leaves, debris, and particulates before rainwater enters the tank. The Silentio adds an additional in line reversible flow filter, providing a second level of filtration. This means finer particles that pass through the first filter are caught before they reach the appliances, resulting in consistently cleaner water delivered to points of use.
Water level reader for accurate rainwater level readings. The Eco-Plus manages the switchover between rainwater and mains backup automatically but does not include a display screen showing the current level of rainwater in the tank. The Silentio adds a water level reader that gives the homeowner a clear, accurate reading of how much rainwater is stored at any time. For homeowners who want visibility of how the system is performing, this is a meaningful addition.
Jet wash cycle to periodically remove debris from the filter. The Eco-Plus filter requires periodic manual inspection to maintain performance. The Silentio adds an automatic jet wash cycle that cleans the filter at regular intervals without any action from the occupant. Over the lifetime of the system, this reduces maintenance requirements and keeps the filter operating at consistent efficiency.
How do the AA Eco-Plus and AA Silentio compare on price?
The AA Eco-Plus starts from £3,042 including VAT. The AA Silentio starts from £3,702 including VAT. Both prices include free UK mainland delivery.
The difference in starting price is £660. Whether that represents good value depends on how much the three additional Silentio features matter for a given project. For self-builders who want a reliable, proven system that operates automatically and requires minimal intervention, the Eco-Plus delivers everything the AA architecture offers at the more accessible price point. For those who want greater visibility of tank levels and the lowest possible long-term maintenance requirement, the Silentio justifies the step up.
It is also worth noting that tank size affects the final price of both systems. A larger tank costs more than a smaller one. The starting prices above reflect the smallest available tank size, so the actual price for a given project will depend on the tank size recommended for the roof area and household demand.
Which rainwater harvesting system suits a straightforward self-build project?
For most self-build projects where the priority is a reliable, compliant system that collects rainwater efficiently and operates without fuss, the AA Eco-Plus is the right choice.
It includes everything the AA architecture delivers: the core separation of mains and rainwater supplies, automatic switchover between rainwater and mains backup, and supply to all non-potable uses in the home. The system operates automatically from commissioning, keeping maintenance requirements low. Both systems carry a Type AA air gap as standard, which is a common compliance approach for non-potable systems under the Water Supply (Water Fittings) Regulations 1999, and both make the Building Control process straightforward for self-build projects.
The AA Eco-Plus is described as: “Practical, efficient, and ideal when you want the AA architecture in a straightforward package”.
Which rainwater harvesting system suits a project that wants more monitoring and control?
For self-builders and homeowners who want greater visibility of how the system performs and the lowest possible maintenance burden over the long term, the AA Silentio is the better fit.
The water level reader gives a clear, real-time view of rainwater levels in the tank at any time, which is useful both for understanding how the system is performing and for planning around dry spells. The reversible flow filter adds a second stage of filtration that the Eco-Plus does not provide. And the automatic jet wash cycle on the filter means the filter maintains itself without periodic manual cleaning.
As water bills continue to rise, and reducing mains water consumption over the long term is a meaningful financial consideration. A system that maintains itself efficiently and keeps the filter performing at its best throughout its operational life contributes to that goal consistently. The Silentio is described as “advanced monitoring and filtration features for projects needing more visibility and control,” which captures the distinction well.
How do you decide between the AA Eco-Plus and AA Silentio for your project?
The decision comes down to two questions. How much visibility do you want of the system’s performance? And how much do you want the system to maintain itself automatically over time?
If the answer to both is “as much as possible,” the Silentio is the right choice. If you want a proven, efficient system that operates reliably without those additional features, the Eco-Plus delivers the same core performance at a lower starting price.
For both systems, the right tank size depends on your roof area and anticipated household demand. Our tank size calculator gives you a personalised recommendation in around two minutes, which is the starting point for a full quote from the GRAF UK team.
Posted by Callum Vallance-Poole, on May 18, 2026.