Rainwater Tanks
PRODUCTS ARRVING SOON
Underground rainwater tanks provide a discreet, high-capacity solution for long-term rainwater harvesting in the UK. Installed below ground level, they allow substantial volumes of water to be stored without impacting garden space or property aesthetics.
With increasing pressure on mains water supplies and more frequent dry periods, below-ground storage offers a practical way to improve water resilience and future-proof your property.
Unlike smaller above-ground water butts, underground tanks are designed for significantly larger capacity and long-term structural performance. Positioned below ground, they are protected from UV exposure and extreme temperature fluctuation, providing stable year-round storage conditions.
At OutdoorOutlet, our underground tanks are selected for strength and durability. Manufactured using heavy-duty roto-moulded materials, they are engineered to withstand ground pressure and typical UK soil conditions when installed in accordance with manufacturer guidance.
Suitable For:
- Larger gardens and landscaped properties
- New build and renovation projects
- Homes seeking increased water independence
- Installations where above-ground space is limited
Many systems can be integrated with pumps and filtration units to supply irrigation systems or external taps, enabling a scalable rainwater storage solution.
Explore the range below to find a discreet, high-capacity underground system built for long-term performance in UK conditions.
There are no products listed under this category.
Why Choose an Underground Rainwater Tank?
Discreet Installation
All storage is hidden below ground, preserving garden layout and visual appeal.
Higher Capacity
Underground systems typically offer significantly greater storage than standard water butts, helping you maintain supply during extended dry periods.
Protected Storage Conditions
Below-ground positioning reduces UV degradation and temperature fluctuation, improving long-term durability.
Scalable Systems
Many underground tanks can be integrated with pumps, filtration units and irrigation systems for expanded functionality.
What Size Underground Tank Do You Need?
Choosing the right size depends on:
1 - Roof surface area
2 - Average rainfall in your region
3 - Intended usage (garden watering vs irrigation system)
4 - Available installation space
Larger properties with extensive roof coverage can collect thousands of litres annually. Proper sizing ensures you maximise storage without overspending on unused capacity.
Built for UK Ground Conditions
Underground tanks must withstand soil pressure, potential surface loading and seasonal ground movement. The systems we supply are selected for structural integrity and long-term outdoor use when installed according to manufacturer guidelines.
For drive-over or traffic-rated applications, ensure the tank specification matches the intended load requirements.