Pillow Tank (Closed Bladder Tank) | A sealed, low-profile bladder made from coated technical fabric or thermoplastic film, with welded seams and dedicated filling, discharge, vent, or inspection fittings. | Approximately 0.5–500 m³ for common project configurations; larger systems may be engineered for specific sites. | Requires a smooth, level base with no sharp stones or protrusions. The tank expands horizontally while filling and has a relatively low visual profile. | Rainwater storage, potable-water reserves when approved materials are used, agricultural water, emergency reserves, and temporary or permanent site storage. | High storage efficiency, low evaporation because the tank is enclosed, limited algae exposure, low transport weight when empty, and fast installation without a rigid frame. | Needs careful site preparation and protection from abrasion, sharp objects, excessive heat, and unauthorized access. It is not designed for internal access while full. | Commonly about 10–20 years when correctly installed, operated, and protected; actual life depends on material, sunlight, temperature, and maintenance. |
Onion Tank (Self-Erecting Open-Top Tank) | An open-top flexible liner supported by a foam or inflatable collar that rises as the tank fills and lowers as the water level falls. | Approximately 0.5–200 m³ for widely used portable and emergency models. | Needs a level, prepared base but normally does not require a metal support frame. The circular footprint is available immediately after deployment. | Firefighting water, disaster response, construction sites, livestock water, wash-down water, and short- to medium-term storage. | Very rapid deployment, easy visual monitoring, simple filling and emptying, and good portability when drained and folded. | Open water is exposed to dust, sunlight, animals, and evaporation. A cover may be needed for hygiene, contamination control, and algae reduction. | Often about 5–15 years under regular outdoor use; service life is affected by UV exposure, handling, and storage conditions. |
Collapsible Frame Tank (Folding Frame Tank) | A flexible liner held by a removable metal or composite frame, usually with an open top and replaceable or repairable liner components. | Approximately 1–100 m³ for common emergency, municipal, and industrial units. | Requires a level base and assembly of the frame. It occupies a defined rectangular or polygonal footprint and can be installed on locations where a self-supporting collar is less suitable. | Emergency water supply, firefighting, utility maintenance, remote worksites, temporary treatment processes, and industrial wash water. | Good wall support, clear usable volume, easy access for inspection and cleaning, and comparatively stable geometry during repeated filling cycles. | Heavier and slower to deploy than a simple pillow or onion tank. Frame components require transport space and can corrode or become damaged if poorly maintained. | Typically about 8–15 years for the liner, while the frame may last longer with corrosion protection and proper maintenance. |
| Baffled Transport Bladder | A flexible bladder containing internal baffles that divide the liquid into compartments and reduce movement during transport by road, rail, or aircraft. | Approximately 0.1–20 m³ for commonly transported water loads; capacity is limited by vehicle payload and handling requirements. | Installed inside a vehicle, transport tray, or approved containment area. It must be restrained and protected against puncture, impact, and excessive bending. | Potable-water delivery, humanitarian logistics, remote-site resupply, military or civil-defense operations, and mobile water distribution. | Reduced liquid surge compared with an unbaffled bladder, efficient empty transport, fast loading and unloading, and suitability for difficult-to-reach locations. | Not normally the first choice for permanent stationary storage. Requires careful load securing, vehicle compatibility, cleaning procedures, and compliance with transport regulations. | Often about 5–10 years, depending on transport frequency, abrasion, folding cycles, UV exposure, and cleaning practices. |
Vertical Flexible Tank (Self-Supporting Cylindrical Tank) | A tall cylindrical flexible reservoir using a reinforced fabric or liner system with a self-supporting wall, collar, or integrated structural arrangement. | Approximately 1–100 m³ for common installations; project-specific designs may exceed this range. | Uses less ground area than a low-profile pillow tank for the same volume, but requires a stable base and adequate clearance around the taller tank wall. | Sites with limited ground area, rainwater harvesting, agricultural storage, process water, and installations requiring a smaller horizontal footprint. | Better land-use efficiency, enclosed configurations can limit evaporation and contamination, and the vertical water column can support convenient gravity-fed layouts. | More sensitive to wind, uneven foundations, and local wall stresses than low-profile designs. A suitable anchoring and base system may be necessary. | Commonly about 10–20 years when suitable materials, foundations, anchoring, and maintenance procedures are used. |