Complete Guide to ISO Tank Codes

ISO tank codes (also called ISO Size–Type Codes) follow the ISO 6346 system: a compact, four-character identifier printed on every tank used in intermodal liquid logistics. Read correctly, the code instantly communicates the tank’s external size, tank category, and design/pressure capability — information that matters for safe loading, transport, inspection and regulatory compliance.

Below is a clear, industry-ready explainer you can use as a blog for BOLT.

What is an ISO Size–Type Code?

An ISO Size–Type Code is a four-character code displayed on the tank frame.

• First two characters (size code) — define external length and height.
• Last two characters (type code) — specify the tank design family and pressure rating / suitability for certain cargos.

These codes are governed by ISO 6346 and related standards (for tank design and testing) and are used alongside IMDG/ADR rules. Operators, depots and inspectors use these codes to match equipment to cargo and to verify compliance quickly.

Decoding the Size Code (first two characters)

• First character — length
• 2 = 20 ft (most ISO tanks are 20 ft long)
• Second character — height
• 2 = 8 ft 6 in (2591 mm) — standard height
• 5 = 9 ft 6 in (2896 mm) — high-cube

Width for ISO tanks is typically ~8 ft (2438 mm) unless otherwise specified. Common size codes you’ll see:

• 22 → 20 ft × 8′6″ (standard)
• 25 → 20 ft × 9′6″ (high-cube)

Decoding the Type Code (last two characters)

The type code shows the tank family and design/pressure category.

Primary letters used for liquid/gas tanks

• K — modern pressurised liquids/gases family (covers a wide range from non-regulated to gas tanks)
• T — older tank designation frequently used in tank/container classification (many T-codes map to common chemical tank designs)
• U — open-top or specialized containers (not used for gas in the same way as K8)

Note: Over time industry usage has aligned many older T-class references with K/N families; always check the tank plate for exact design data.

K-series breakdown (common practical interpretation)

• K0 — Non-regulated liquid tanks (food-grade or mild liquids)
• K1 — Dangerous goods with ≤ 2.65 bar design pressure (low pressure chemicals)
• K2 — Dangerous goods > 2.65 bar up to ≤ 10 bar (general chemical use)
• K3 — Dangerous goods > 10 bar (higher pressure liquids)
• K8 — Gas tanks / high-pressure gases

T-series in practice

• T3 – T6 — Liquid tank containers used for chemicals/hazardous cargo; pressure/design varies by numeric value.
• Example: T5 typically represents a design capable of medium pressure (often cited ~4 bar min).
• T6 generally maps to higher pressure designs (T14-like behavior in older nomenclature).

Common ISO Tank Code Examples:

Code	Dimensions	Type Description	Typical Use Case
22K0	20 ft x 8'6"	Pressurised tank container (liquids and gases) Liquid tank non-regulated goods	Food-grade or mild liquids ​
22K1	20 ft x 8'6"	Pressurised tank container (liquids and gases) Liquid tank dangerous goods ≤ 2,65 barc pressure	Low-pressure chemicals ​
22K2	20 ft x 8'6"	Pressurised tank container (liquids and gases) Liquid tank dangerous goods >2,65 barc and ≤ 10 barc pressure	General chemicals ​
22T5	20 ft x 8'6"	Pressurised tank container (liquids tanks) dangerous goods 4.0 barc pressure	Corrosive liquids, T11-like ​
22T6	20 ft x 8'6"	Pressurised tank container (liquids tanks) dangerous goods 6.0 barc pressure	T14 equivalents ​
22K8	20 ft x 8'6"	Pressurised tank container (liquids and gases) Gas Tank	High-pressure gases ​

Note: UN T-codes (T11/T14) relate loosely via design but differ from ISO size-type codes.​

Step-by-Step Decoding

Take 22T5 as an example:

1. First digit = 2 → 20 ft length.

2. Second digit = 2 → 8′6″ height.

3. Third character = T → Tank container family (chemical/hazardous liquid application).

4. Fourth character = 5 → Design/pressure category (medium pressure; chemical service).

Apply the same steps for any four-character code; use BIC/ISO tables or the tank’s data plate to confirm exact pressure ratings and fittings.

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Why ISO Tank Codes matter

• Prevent cargo-to-tank mismatches (critical for safety).

• Support regulatory compliance under IMDG / ADR rules.

• Guide depot maintenance, cleaning and testing intervals.

• Help operators and shippers choose appropriate equipment for chemicals, pharma, food-grade and gases.

Always verify the tank plate (data/name plate) and the operator’s documentation for the definitive design pressure, test history and approvals.

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Final notes & best practice

• The four-character ISO Size–Type Code gives a fast, standardised snapshot — but it’s not a substitute for the tank data plate or technical documentation.

• When in doubt about pressure limits, lining, fittings or cargo compatibility, consult the tank plate, the operator and the official BIC/ISO resources.

• Use the code to shortlist equipment; always confirm the full technical specification before loading.