Two formats dominate the flexible water tank market: pillow tanks and cube tanks. Both are made from the same coated fabric materials and both serve water storage and transport applications. The choice between them is almost always determined by site conditions, footprint requirements, and how the tank will be moved, installed, and maintained.

What Is a Pillow Tank?

A pillow tank — also called a bladder tank or onion tank — is a flat-bottomed, dome-topped flexible tank that rests directly on the ground and fills vertically. The profile resembles a cushion or pillow when full. Most pillow tanks have a large flat base with the volume rising upward, stabilised by the weight of the liquid inside.

Pillow tanks are the most widely used flexible tank format globally. They are well established in agriculture, construction water supply, emergency relief, bushfire fighting, and aquaculture.

What Is a Cube Tank?

A cube tank is a flexible bladder designed to sit inside a rigid cage or IBC (Intermediate Bulk Container) frame. The cage gives the tank a defined rectangular footprint and keeps it structurally upright without relying on ground support alone. Cube tanks match the standard 1,000-litre IBC format in many cases, though custom sizes are produced for specific cage dimensions.

Cube tanks are common in industrial liquid storage, chemical handling, and logistics applications where tanks must stack, palletise, or interface with existing IBC handling infrastructure.

Key Differences

Footprint and Ground Requirements

Pillow tanks require a level, compacted surface without sharp objects. They spread horizontally as they fill, so the base area at capacity may be significantly larger than the collapsed footprint. For large capacities — 10,000 litres and above — the ground surface and support structure matter considerably.

Cube tanks rely on the rigidity of the outer cage, so they can be placed on pallets, concrete pads, or within racking systems. They do not require a specially prepared ground surface in the same way.

Stackability and Logistics

Cube tanks inside IBC frames can be stacked (typically two high when empty, one high when full). They can be moved by forklift, placed on standard pallets, and handled through standard warehouse and transport logistics.

Pillow tanks are not stackable. They are transported folded and flat, which makes them highly compact for export and long-distance shipping, but once deployed they occupy a fixed ground area.

Capacity Range

Pillow tanks scale across a very wide capacity range — from 100 litres to over 500,000 litres. This makes them the practical choice for large-volume applications: irrigation reservoirs, emergency water supply for communities, and bulk storage on remote sites.

Cube tanks are typically produced in the 300–1,000 litre range, constrained by the dimensions of standard IBC cages. Larger custom formats are possible but require a matching custom cage, which increases cost.

Installation and Setup

A pillow tank requires site preparation (clearing, levelling, and often a ground sheet or protective layer) and is then unfolded and connected to an inlet. For large tanks, this is a manual multi-person process.

A cube tank is placed in its cage, the cage is positioned as required, and the bladder is connected to inlet and outlet fittings. Setup is faster for a single unit, but does not scale as easily to very large volumes without adding multiple cages.

Maintenance and Cleaning

Pillow tanks can be drained, collapsed, and inspected or cleaned without removing any outer structure. The tank itself is accessible at all seams.

Cube tank bladders can be removed from their cages for inspection and cleaning, but this involves disassembling or opening the cage, which adds a step to the maintenance process.

Which Format Should You Specify?

Choose a pillow tank when:

  • Capacity exceeds 2,000 litres
  • The tank will be deployed outdoors on a prepared ground surface
  • The application is agricultural, construction site water, emergency relief, or bulk storage
  • Transport cost per litre needs to be minimised (pillow tanks fold flat, maximising shipping efficiency)
  • The site is remote and heavy lifting equipment is not available

Choose a cube tank when:

  • Capacity is in the 300–1,000 litre range per unit
  • The tank must fit within a standard IBC cage or existing frame infrastructure
  • Forklift handling or pallet racking is part of the logistics plan
  • The application involves chemical storage, industrial liquids, or frequent relocation
  • Multiple units will be stacked or stored in a warehouse environment

Material Applies to Both Formats

Both pillow tanks and cube tanks are produced in PVC or TPU-coated fabric. The material selection criteria are the same regardless of format: application, operating temperature, liquid compatibility, and handling frequency. See the Flexible Water Tank Buyer's Guide for a detailed comparison of PVC and TPU.

Ordering from ZolinWorks

ZolinWorks manufactures both pillow tanks and cube tank bladders at our Hangzhou facility. All formats are produced using our in-house HF welding equipment and inspected before packing. Custom sizes, fittings, and colour options are available across both formats.

To request a specification and quote, contact us with your required format, capacity, liquid type, fitting configuration, destination, and order quantity. We typically respond within one business day.