carat xl underground water tank
carat xl underground water tank
Klaro Two Tank System
klaro xxl tanks

Carat 8500L-52000L XL/XXL Underground Water Tank

£2,789.34£16,959.94 inc VAT

Large-capacity underground water tank for a diverse range of applications.


FREE Delivery by Wednesday, 05 June, 2024.


Protecting you



Extensive Storage Capabilities: The Carat XL/XXL Underground Water Tank is designed to handle a wide array of storage needs, accommodating non-potable water, wastewater, raw sewage, effluent, silage, slurry, rainwater, greywater, and blue water. This flexibility makes it perfectly suited for extensive residential, agricultural, or industrial applications where large-volume storage solutions are crucial.

Substantial Size Range: With capacities ranging from 8500L to a massive 52,000L, the Carat XL/XXL Tanks cater to all scales of storage requirements. This range allows users to select the perfect size to meet their needs, ensuring efficient space utilisation and optimal storage management.

Ready for Immediate Use: Delivered fully assembled, these tanks streamline the installation process, significantly reducing on-site labour and setup time. The preassembled delivery ensures that the tanks can be quickly integrated into existing systems or new projects with minimal disruption.

Optional Vehicle Loading Lid: An optional vehicle loading lid is available for installations requiring placement under drivable surfaces, such as driveways or parking areas. This lid allows the tank to withstand heavy loads, ensuring safety and durability even under high traffic conditions.

Assured Longevity with Warranty: The Carat XL/XXL Tanks have a 10-year warranty, demonstrating the manufacturer’s confidence in their durability and construction quality. This warranty provides long-term security and peace of mind for your investment.

Stable in Varying Groundwater Conditions: These tanks are designed to be groundwater stable up to the middle of the tank, featuring an extremely stable construction that protects against water ingress and structural damage, even in high groundwater areas.

Customisable Installation Options: Adjustable lid heights allow seamless flush alignment with ground level, providing a discreet and unobtrusive installation. Compatible tank domes, risers, and lids are available to meet specific invert-level requirements, ensuring that each installation is tailored to the site’s unique needs.

Guaranteed Watertight Integrity: All connections between the tank dome, riser, and lid are sealed with high-quality thick rubber gaskets, creating watertight seals that prevent leaks and contamination, safeguarding the environment and the stored substances.

Flexible Backfill Choices: Depending on site-specific ground conditions and groundwater levels, the Carat XL/XXL Tanks offer granular or concrete backfill options. This flexibility allows for optimal adaptation to varying site conditions, ensuring the stability and integrity of the installation.

Opt for the Carat XL/XXL Underground Water Tank if you require a robust, versatile, and sizable underground storage solution. Its comprehensive range of features and extensive capacity options make it an ideal choice for handling significant storage demands in various settings.

Images are for illustrative purposes only, there is a possibility that certain products may have been upgraded or replaced with equivalent alternatives.

What’s included

Supplied by Graf

  • Underground tank & dome (choice of tanks available, sizes vary according to application type).
  • Pedestrian telescopic lid as standard, 3.5 tonnes vehicle loading adjustable lid available on request.
  • Tank supplied with 1x lid and dome & 1x tank dome plug. (8,500L – 16,000L)
  • 2nd maxi tank dome and telescopic lid available upon request. (22,000L – 52,000L)
  • Extension risers available on request.

Supplied by Others

  • Inlet/outlet drainage pipework.
  • Connecting pipework between multiple tank systems.

System Benefits

  • Simple & quick to install
  • High-quality, robust, polypropylene tank & related accessories for use with a wide range of media
  • Adjustable lid height for flush alignment to ground level
  • The pedestrian telescopic lid as standard, 3.5 tonnes cast iron adjustable lid available on request
  • Fully compatible tank domes, risers & lids to deal with invert-level requirements
  • All tank dome, riser & lid connections include high-quality thick rubber gasket for watertight seals
  • Granular or concrete backfill options, subject to ground conditions & groundwater level.

Product Dimensions, Levels & Weights

Product Dimensions, Levels & Weights

Carat XL/XXL Tank Dimensions & Weights (8500L – 52000L)

Carat XL 8500L | Download
Carat XL 10000L | Download
Carat XXL 16000L | Download
Carat XXL 22000L | Download
Carat XXL 26000L | Download
Carat XXL 32000L | Download
Carat XXL 36000L | Download
Carat XXL 42000L | Download
Carat XXL 46000L | Download
Carat XXL 52000L | Download

Carat XL Installation and Maintenance Instructions | Download
Carat XXL Installation and Maintenance Instructions | Download

CARAT Tank Levels Mini Dome | Download
CARAT Tank Levels Maxi Dome | Download

Mini & Maxi Lid Dimensions

PE Mini Lid (Pedestrian Loading 371010) | Download

PE Maxi Lid (Pedestrian Loading 371011) | Download

Vehicle Loading Lid (371052) | Download

Extension piece options

Extension Sleeve (371003) | Download

Extension Sleeve (371015) 1000mm | Download


Carat Tank (Levels, Maxi Dome) | Download

Carat Tank (Levels, Mini Dome) | Download

Carat XL Installation Instructions | Download

Carat XXL Installation Instructions | Download

Carat XXL | Download


Specification Sheet | Download

Installation & Commissioning

This informative guide covers the following:

  • Loading information
  • Tank coverage heights
  • Excavation dimensions
  • Technical & general data
  • Installation & Assembly

Read the Guide Carat XL Instructions | Download

Read the Guide Carat XXL Instructions | Download


Service Provider Support

Graf UK has a national service provider network of contractors who can offer various services including the installation of our tank systems.

Coming Soon: New UK map with the service provider/installer contact details.

Delivery Information

Please note the following regarding Graf UK deliveries

We’re still delivering to our customers safely via our own delivery vehicles & drivers in the main, using external hauliers when required.


This gives us much greater control & flexibility over our deliveries.


All orders are typically delivered within 5-7 working days from receipt of order, however during this time due to UK-wide disruption, some deliveries may take a little longer and we would still aim to deliver within 10 days.


• Delivery lead time is 5-7 working days on all orders, unless otherwise advised.
• Price includes delivery to mainland UK.
• Please check for deliveries into Cornwall, Mid & Northern Scotland & Isles as additional delivery charges may be applicable.
• We cannot currently provide a tracking number for all orders but can accept customer enquiries by phone.
• Off-loading by the customer unless agreed otherwise.
• Tanks are generally strapped to a pallet for fork lift off-load, slings can also be used.
• Please advise if there is restricted access to site or special delivery instructions.