Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 1
Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 2Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 3Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 4Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 5Cover preview — API 653 Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition, Includes Addendum 1 (2018), Addendum 2 (2020), Addendum 3 (2023), Addendum 4 (2025), Errata 1 (2020), and Errata 2 (2025) — Page 6
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API Std 653 — Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition — Includes Addenda 1–4 & Errata 1–2

API 653 Tank Inspection, Repair, Alteration, and Reconstruction — Fifth Edition (with Addenda 1–4 and Errata 1–2). Published by the American Petroleum Institute (API).

API 653 American Petroleum Institute (API) Fifth Edition
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About this publication

The API Standard 653 — Tank Inspection, Repair, Alteration, and Reconstruction, Fifth Edition is the American Petroleum Institute’s primary standard for the inspection, evaluation, repair, alteration, relocation, and reconstruction of aboveground steel storage tanks that have already been placed in service.

This updated edition includes the complete published Fifth Edition update sequence through 2025:

API’s Standards Plan confirms that Addendum 4 was published July 15, 2025, making this substantially more current than copies of API 653 that include only the earlier 2018, 2020, or 2023 updates.

API 653 applies primarily to steel storage tanks constructed to API Standard 650 and its predecessor API Specification 12C. Its purpose is to establish minimum requirements for maintaining the structural and mechanical integrity of these tanks after they enter service.

The standard addresses the parts of a tank most critical to continued safe operation, including the:

This makes API 653 one of the central references used by aboveground storage tank inspectors, owner/operators, mechanical-integrity departments, tank engineers, repair contractors, NDE personnel, corrosion specialists, petroleum facilities, terminals, refineries, and tank-maintenance organizations.

Unlike API 650, which primarily addresses the design and construction of new welded storage tanks, API 653 is focused on what happens after a tank has been placed into service.

That includes determining whether an existing tank remains suitable for continued operation, how long it can safely remain in service, what inspection interval is appropriate, when repairs are required, whether alterations are acceptable, and how major reconstruction or relocation work must be performed.

Tank Inspection and Condition Assessment

Inspection is at the heart of API 653.

The standard establishes requirements and guidance for assessing the condition of existing tanks through methods such as:

The inspection process is used to identify deterioration that could affect continued safe operation.

Common concerns include:

API 653 provides the framework for evaluating these conditions rather than simply requiring a tank to be removed from service whenever deterioration is discovered.

Remaining Thickness and Corrosion Evaluation

One of the most important applications of API 653 is determining whether the remaining thickness of tank components is sufficient for continued operation.

The standard includes requirements for evaluating:

Tank-bottom evaluation is particularly important because underside corrosion may not be visible during routine external inspection.

API 653 therefore recognizes inspection methods including magnetic flux leakage (MFL) and ultrasonic thickness measurement (UT) for evaluating tank bottoms.

The 2025 Addendum 4 further revises the requirements associated with tank-bottom plate thickness measurements and references API Recommended Practice 575, continuing API’s effort to improve the technical framework for storage-tank inspection.

Inspection Intervals

API 653 establishes criteria for determining appropriate intervals between inspections.

The standard addresses both:

Inspection intervals can depend on factors including:

This allows owner/operators to establish inspection programs based on actual tank condition and risk rather than relying entirely on arbitrary fixed schedules.

Risk-Based Inspection

API 653 permits the use of Risk-Based Inspection (RBI) principles in applicable situations.

RBI can incorporate factors such as:

When API 653 does not provide specific evaluation procedures for a particular degradation mechanism, or when the standard specifically permits it, API 579-1/ASME FFS-1 Fitness-For-Service may be used to perform more detailed engineering assessments.

Tank Bottom Inspection

The tank bottom is one of the most critical components addressed by API 653.

Bottom inspection provisions include consideration of:

API 653 provides methods for predicting the minimum remaining bottom thickness at the end of the next inspection interval, helping owner/operators determine whether a bottom can remain in service or requires repair, lining, replacement, or a shorter inspection interval.

Shell Evaluation

The standard provides requirements for evaluating the tank shell for conditions including:

Shell evaluation helps determine whether a tank retains sufficient structural capacity under its intended operating conditions.

Tank Settlement

Tank settlement can significantly affect shell stresses, bottom integrity, piping connections, roofs, and overall tank performance.

API 653 therefore includes procedures and acceptance considerations for evaluating conditions such as:

These evaluations can help determine whether continued operation, monitoring, engineering analysis, or corrective work is appropriate.

Repairs and Alterations

API 653 establishes requirements for performing repairs and alterations on in-service tanks.

Covered work includes areas such as:

The standard addresses welding, materials, design considerations, examination, testing, documentation, and acceptance of completed repairs.

Reconstruction and Relocation

API 653 also addresses tanks that are:

Requirements are provided for evaluating existing components and determining which materials may be reused.

The standard also covers welding, examination, dimensional tolerances, foundations, testing, and other requirements applicable when a tank is reconstructed at another location.

This makes API 653 particularly valuable for organizations attempting to extend the useful life of existing storage assets rather than replacing complete tanks unnecessarily.

Welding and Examination

Many of the design, welding, examination, and material requirements originally established by API 650 continue to influence work performed under API 653.

However, API makes an important distinction: when there is an apparent conflict between API 653 and API 650 for a tank that has already been placed in service, API 653 governs the in-service tank work.

The standard therefore interacts closely with references such as:

This broader standards relationship is why API 653 is such an important part of refinery, terminal, petroleum-storage, and mechanical-integrity programs.

API 653 Inspector Certification

API Standard 653 also provides the technical foundation for the API 653 Aboveground Storage Tank Inspector Certification Program.

API describes the certification program as establishing a uniform national qualification framework for professionals involved in inspection and repair of aboveground storage tanks. API 653 inspector certification is accredited to ISO 17024 requirements and is valid for a three-year certification term.

The standard is therefore particularly relevant to:

Important Exam Note

The standard sold here includes Addendum 4 (July 2025).

However, API’s publication effectivity sheet for the March, July, and November 2026 API 653 certification exams lists API 653 Fifth Edition with:

and does not currently list Addendum 4 as part of the 2026 examination reference set.

Certification candidates should therefore always follow the API Publications Effectivity Sheet for their specific examination date rather than assuming every current publication update is immediately examinable.

Includes All Published Updates Through July 2025

Addendum 1 — April 2018

Provides the first major set of revisions to the original 2014 Fifth Edition.

Errata 1 — March 2020

Corrects technical and editorial issues identified following publication.

Addendum 2 — May 2020

Provides additional updates to inspection, evaluation, repair, and related requirements.

Addendum 3 — November 2023

Updates the Fifth Edition with further technical revisions reflecting current tank inspection and integrity practices.

Errata 2 — February 2025

Provides the latest published corrections preceding Addendum 4. API’s 2026 certification effectivity sheet confirms Errata 2 as February 2025.

Addendum 4 — July 2025

The latest published addendum to the Fifth Edition.

API’s Standards Plan records API 653-A4 as published July 15, 2025.

The update includes revisions involving tank-bottom inspection and thickness measurement, including updated references to API RP 575 and revisions to Section 4.4.4 concerning evaluation of bottom-plate corrosion.

Why This Standard Matters

API Standard 653, Fifth Edition with Addenda 1–4 and Errata 1–2 is an essential reference for:

Product Features

Product Details

Title: API Standard 653 — Tank Inspection, Repair, Alteration, and Reconstruction
Publisher: American Petroleum Institute (API)
Edition: Fifth Edition
Original Publication: November 2014
Catalog Publication Date: November 1, 2014
Original Fifth Edition Pages: 162
Current Consolidated Publication: Approximately 192 pages
API Product Number: C65305
Language: English
Status: Current Fifth Edition
Primary Application: In-service aboveground welded steel storage tanks

Updates Included:

Subject: Storage Tanks / Tank Inspection / Tank Repair / Mechanical Integrity / Petroleum Storage / Aboveground Storage Tanks / API Inspection

Current Edition Status

The Fifth Edition with Addenda 1–4 and Errata 1–2 remains the current API Standard 653 publication.

API’s standards-development plan currently lists a Sixth Edition of API 653 as being developed, but no replacement publication date is shown. Until that new edition is formally published, the updated Fifth Edition remains the applicable current publication.

Regulatory Relevance

API 653 is also referenced in U.S. regulatory frameworks involving storage tanks.

In June 2026, PHMSA proposed updating federal pipeline-safety regulations to incorporate API 653 Fifth Edition including Addenda 1–4 and Errata 1–2, replacing the much older Third Edition referenced by existing rules. The proposal specifically identifies the complete update sequence through July 2025.

This underscores the continuing importance of the current Fifth Edition for tank integrity, inspection, repair, and regulatory work.