Flexitank basics
A flexitank is a large, flexible bag that turns a standard 20-foot dry container into a bulk liquid tank. It is laid on the container floor, held back from the doors by a bulkhead, filled through a valve and discharged at destination. Flexitanks are generally single-use and carry non-hazardous liquids such as edible oils, glycerin, wine, juice concentrates, latex and base oils. Because the container travels as ordinary dry cargo, a flexitank shipment can use the container network by sea, rail and road.
A single-layer flexitank uses one heavier polyethylene layer as the liquid barrier, usually inside a woven outer layer. A multi-layer flexitank uses several thinner polyethylene film layers inside a woven polypropylene outer layer, so the film in contact with the cargo is backed by additional layers. Buyers choose based on the cargo, route, handling conditions and carrier requirements. A common multi-layer construction is 4-layer polyethylene film (125 micron) with a woven polypropylene outer layer. If you have a specific construction requirement, state it when you request quotes.
A flexitank carries roughly 18,000 to 24,000 liters in one 20-foot dry container and is used once. An ISO tank is a reusable stainless-steel tank in a frame; it can carry hazardous cargo but must be cleaned and repositioned after each trip. IBCs hold about 1,000 liters each and drums about 200 to 210 liters, so they suit smaller volumes but involve more handling and packaging per liter. For non-hazardous liquids moving in full-container volumes, a flexitank is often the simpler option. For smaller lots, 1,000 L IBCs, including paper (corrugated) IBCs, are an alternative.
The savings usually come from what a flexitank avoids. There is no return trip and no tank cleaning, as there is with an ISO tank. A 20-foot container with a flexitank typically carries more liquid than the same container loaded with drums or IBCs, with less packaging to buy, handle and dispose of. Standard dry containers are widely available, which can simplify equipment planning. Actual savings depend on your cargo, volumes, route and carrier rates, so compare the total delivered cost per liter, including the flexitank price delivered to your loading site.
Sizes and specifications
Flexitank sizes are stated as nominal capacity in liters. Shorthand such as FT-18 or FT-24 refers to the capacity in thousands of liters, so FT-18 means an 18,000 L flexitank and FT-24 means 24,000 L. Flexitanks for standard 20-foot dry containers typically come in sizes such as 18,000 L, 20,000 L, 21,000 L, 22,000 L, 23,000 L and 24,000 L. Not every supplier's range includes every intermediate size; a 19,000 L size, for example, is not always offered. When you order, confirm the size by its liter capacity.
Size depends mainly on cargo density and weight limits. Multiply the flexitank volume by your cargo's density to estimate the cargo weight, then check it against the container's payload limit and the road weight limits on your trucking legs. For example, 22,000 L of a liquid at 0.92 kg/L weighs about 20,240 kg. Denser cargoes, such as some syrups and concentrates, usually need a smaller size like 18,000 L or 20,000 L; lower-density liquids can use 23,000 L or 24,000 L. Share your product and its density with your supplier for a size recommendation.
A flexitank specification covers the film construction, the outer layer, the loading and discharge arrangement, the valve and the bulkhead. A common standard specification for a standard 20-foot dry container is 4-layer polyethylene film (125 micron) with a woven polypropylene outer layer, bottom load, bottom discharge (BLBD), and a 3-inch ball valve, with other valve options on request. A set commonly includes a cardboard bulkhead and steel bulkhead bars, and heater pads can be added for cargoes that need heating before discharge. Flexitanks of this type are for non-hazardous liquids only. Ask for the full specification sheet with any quote.
Most flexitanks use a valve at the door end for both loading and discharge, known as bottom load, bottom discharge (BLBD). A 3-inch ball valve is a common standard because it connects to typical hoses and fittings, with adapters where needed. Some loading sites or receivers need a different fitting or valve type to match their equipment, so confirm the connection at both ends before shipping. Other valve options can usually be requested; mention your fitting requirements when you ask for a quote.
Some cargoes thicken or solidify at lower temperatures, which can make discharge slow or impossible without heat. Depending on the season and route, this can include certain edible oils and fats, glycerin and other viscous liquids. A heater pad is laid on the container floor beneath the flexitank before loading. At destination, the receiver connects it to a suitable heat source and warms the cargo before discharge, so the receiver needs the right equipment and time. Heater pads are typically ordered as an option, so describe your cargo and route when you ask for pricing.
The bulkhead holds the filled flexitank back from the container doors. A typical bulkhead combines steel bars fitted across the door end of the container with a cardboard or similar board behind them, so the pressure of the liquid is taken by the bars rather than the doors. A correctly fitted bulkhead also helps protect the people who open the doors at destination. Flexitank sets commonly include a cardboard bulkhead and steel bulkhead bars, but confirm what a set includes before you order, and ask for guidance on bulkhead fit-up and container preparation before the first fill.
Cargo suitability
Flexitanks are used for bulk non-hazardous liquids. Common examples include edible and vegetable oils, glycerin, wine, juice concentrates, syrups and other food ingredients, latex, lubricants and base oils, non-hazardous liquid fertilizers and non-hazardous chemicals. Suitability depends on the specific product, not only its category: density, temperature, viscosity and compatibility with the flexitank film all matter. Check the product's safety data sheet to confirm it is not classified as hazardous for transport. If you are unsure, check with your flexitank supplier and carrier before you book.
Flexitanks are not used for dangerous goods. Liquids classified as hazardous for transport, such as flammable, toxic or corrosive products, need packaging approved for that class, typically ISO tanks or other approved containers. Flexitanks are also a poor fit for cargo that must be kept under pressure, cargo that is not compatible with polyethylene, and products that need temperature control during transit. Check the product's classification on its safety data sheet and confirm with your carrier and flexitank supplier if you are unsure about a product.
Many food liquids, such as edible oils, wine, juice concentrates and syrups, are commonly shipped in flexitanks. For food cargo, receivers often ask for documentation on the flexitank materials, along with a clean, dry, odor-free container and careful hygiene during loading. Requirements vary by product, receiver and destination country, so agree them with your buyer before shipment. Ask your flexitank supplier for product specifications and material documentation for your shipment files, and confirm what it can supply against your receiver's requirements.
Containers, loading and discharge
Flexitanks are used in standard 20-foot dry (general-purpose) containers. The container should be structurally sound, clean, dry and odor-free, with an intact floor, no holes, no protruding nails, screws or sharp edges, and doors and locking bars that work properly. Damaged side walls or door-end posts can be a problem once the flexitank is full. Some carriers set their own container standards for flexitank use, so check with your ocean line. If this is your first flexitank shipment, ask your supplier for container preparation guidance.
Inspect the container inside and out before fitting a flexitank. Check the floor for damage, nails and screws; the walls and roof for holes and dents; and the door-end posts and locking gear. A light test with the doors closed can reveal small holes. Clean and dry the interior, and line the floor and walls with cardboard or a similar liner where required. Then lay out the flexitank with the valve at the door end, place any heater pad and install the bulkhead. Ask your supplier for fit-up and loading guidance before your first fill.
Once the container is prepared and the bulkhead installed, the loading hose is connected to the flexitank valve, usually from a tank truck, rail car or storage tank. The liquid is pumped in at a controlled rate while the flexitank is watched as it fills and settles evenly. Filling stops at the agreed volume, normally close to the rated capacity, which helps limit surge in transit. The valve is then closed and secured, and the container is labeled as carrying a flexitank. Record the loaded quantity for your documents.
At destination, the receiver checks the container and bulkhead before opening the doors carefully. If the cargo needs warming, the heater pad is connected and the cargo is heated first. The discharge hose is connected to the valve, and the liquid is pumped out or drained by gravity, depending on the receiver's equipment. Some receivers tilt the container slightly near the end to drain the remaining liquid. The empty flexitank and bulkhead are then removed and the container is returned. Confirm the receiver's fittings and heating needs before you ship.
Flexitanks are generally single-use. After discharge, the flexitank is drained as fully as practical and removed from the container. It consists mostly of polyethylene and polypropylene. Whether it can be recycled depends on the cargo residue and on the facilities available near the receiver; otherwise it is disposed of as waste under local rules. Receivers should plan disposal before the shipment arrives, as part of their discharge procedure. Ask your flexitank supplier for materials information to share with the receiver for its disposal or recycling arrangements.
Buying flexitanks in the US
Yes. Flexitanks are stocked in the US, for example in Houston, Texas, in sizes from 18,000 L to 24,000 L, and some suppliers also stock bulkheads and 1,000 L paper IBCs. Availability changes with demand, so ask the supplier to confirm availability and a ship date with every quote. Buying from US inventory lets you plan your loading around a confirmed ship date and a domestic delivery.
Lead time depends on stock levels, quantity and the delivery location. Orders filled from available US inventory can ship once the order is confirmed, followed by transit time to your loading site. Larger programs or specific valve or heater pad requirements may need more planning. Ask for availability and a ship date with every quote, so you know the timing before you commit. For a time-sensitive shipment, include your loading date in your quote request.
Minimum orders vary by supplier, and some have no fixed minimum, quoting single units as well as larger, recurring programs. For a one-off shipment, a single flexitank with its bulkhead set can be supplied. For a regular shipping program, share your expected volumes and frequency so the supplier can plan stock and deliveries with you. Pricing depends on size, quantity, options and delivery location, so ask for current pricing with each quote.
Flexitanks are delivered folded and packed, so they travel compactly to the loading site, where they are fitted into the container. Delivery cost and timing depend on your location and quantity, so ask for both with your quote. If you load at more than one site, share each address. Some suppliers can also arrange ocean freight on request. Include your loading address and timing when you request a quote.
Yes. US exporters, freight forwarders and 3PLs buy flexitanks for shipments of non-hazardous liquids leaving the US. The flexitank is delivered to the US loading site and fitted into a 20-foot container there, and the loaded container then moves by truck or rail to the port. Check early that your ocean carrier accepts flexitank cargo on the route and that the receiver has suitable discharge equipment.
Requirements vary by carrier, cargo and receiver, so ask early. Ocean carriers often have their own flexitank acceptance rules, which may cover supplier approval, liability insurance for the flexitank and evidence of testing. Many refer to industry guidance such as the Container Owners Association (COA) code of practice for flexitanks. Shippers usually provide a Certificate of Analysis for the cargo, and food receivers may ask for material documentation. Ask your flexitank supplier for product specifications and documentation for your shipment files, and confirm which documents your carrier and receiver need.
Contact a flexitank supplier with your product and its density, the volume and number of flexitanks, the loading location and timing, any valve or heater pad requirements, and whether you need ocean freight. A complete request lets the supplier reply with a size recommendation, pricing and availability, and confirm a ship date. If you are new to flexitanks, ask for help with size selection and loading guidance before you order.