Double Wall Tanks

Double-wall tanks: liquid storage with integrated containment

A double-wall tank includes an inner tank that holds the liquid and an outer enclosure that provides containment if the inner tank leaks. This configuration can be considered for storing chemical or corrosive products when the project requires secondary containment.

Within our plastic tank range, double-wall tanks combine storage and containment in a single assembly. However, the liquid, operating conditions and connections must be validated before selecting the configuration.

Double-wall tank or tank in a containment basin?

These configurations address a containment need, but their installation and access differ.

A double-wall assembly can reduce the space occupied compared with a tank placed in a separate rectangular basin. The actual space savings depend on the selected dimensions and the clearance needed for maintenance.

To compare the options, consider our closed-top vertical tanks and our secondary containment basins. The choice must account for the complete installation, rather than only the volume to be stored.

Validate the liquid and its operating conditions

The versions listed are made of UV-treated HDPE and have a nominal specific gravity rating of 1.9 at 20 °C. A range with a specific gravity rating of up to 2.2 is available on request, subject to confirmation of the configuration.

Specific gravity does not determine everything. A liquid may meet this rating while requiring a different selection because of its composition, concentration or temperature. Compatibility must cover the tank, fittings, gaskets and accessories in contact with the product.

For projects in agriculture or food processing, specify the exact product to be stored. The industry alone does not establish compatibility.

Our section on tank applications presents the main usage contexts.

Plan connections without compromising containment

The tanks offered include a lid but are supplied without a drain, vent or level indicator. These components are selected according to the project. The liquid is normally withdrawn through the top using a pump.

An important point at Agrico: we validate connection locations before ordering. Adding an outlet as you would on a single-wall tank can compromise the function of the outer enclosure. Any connection through both walls requires a specially adapted and validated configuration.

Bulkhead fittings and ball valves must therefore be considered according to the planned assembly, without assuming that a standard accessory is suitable.

The selection of tank vents must account for filling, draining and potential fumes. The tanks offered cannot be pressurized.

To monitor the contents, a suitable level measurement system must be planned: the outer wall does not allow the liquid level in the inner tank to be read directly. Level indicators are not automatically compatible with every double-wall configuration.

Prepare the installation before delivery

Before ordering, confirm:

• The liquid, its concentration, specific gravity and actual operating temperature.
• The volume to be stored and the project’s containment requirements.
• Access to the room and the available space above the tank.
• The filling, pumping, venting and level measurement connections.
• The supporting surface and access for inspection.

The tanks offered are free-standing with flat bottoms and are intended for above-ground use. They must rest on a flat, smooth surface suitable for the load.

Frequently asked questions

Does a double wall guarantee chemical compatibility?

No. It provides secondary containment, but compatibility of the liquid with the materials and operating conditions must be validated separately.

Can a drain be added at the bottom?

A bottom outlet requires a configuration adapted to both walls, to be validated before ordering. The outer enclosure must not be drilled like an ordinary tank.

Are the drain, vent and level indicator included?

No. These components must be planned according to the liquid and how your installation operates.