FRP Tank Standards: ASTM D3299-26 (replaces D4097) and ASME RTP-1

In short: Most FRP chemical storage tanks are specified to one of three documents. ASTM D3299 covers above-ground vertical cylindrical tanks for aggressive chemicals at atmospheric pressure. Since the 2026 edition (D3299-26) it covers both filament-wound and contact-molded tanks, and it supersedes ASTM D4097, the old contact-molded tank standard, which ASTM withdrew in 2026. ASME RTP-1 is a fuller code for stationary vessels up to 15 psig internal or external pressure, with fabricator certification and inspection rules. In Europe, EN 13121 covers GRP tanks and vessels up to 10 bar. FIBROVX builds FRP tanks to order. Diameter, height, resin system, nozzles, color and accessories can all be customized to your project specification.

Why the standard matters for an FRP tank

An FRP tank is a pressure-free or low-pressure structure made of a laminate, not a homogeneous metal plate. Its strength depends on the resin, the glass, the layer sequence and the workmanship. A tank standard turns those variables into rules that two suppliers can both quote against. A good tank standard does four things:

• It sets minimum laminate requirements, such as the corrosion barrier and the structural layer.
• It gives a design basis, such as how thick the shell must be for a given height, specific gravity and diameter.
• It defines workmanship and appearance, with limits on visual defects.
• It defines tests and inspection, such as Barcol hardness for cure and glass content.

Without a named standard, two quotations for "a 20 m³ FRP tank" can describe very different products. The standard is the shortest way to make them comparable.

The standards at a glance

Two groups appear here. ASTM D3299 is a product specification. It is the usual choice for standard atmospheric storage. ASME RTP-1 and EN 13121 are fuller design codes. They suit pressurized, vacuum or critical service, or projects where the owner wants stress analysis and formal inspection.

ASTM D3299: the workhorse specification

ASTM D3299 is the most cited FRP tank specification in industrial purchasing. In its 2026 edition the title is Standard Specification for Glass-Fiber-Reinforced Thermoset Resin Corrosion-Resistant Tanks. The scope covers:

• cylindrical tanks for above-ground vertical installation;
• tanks fabricated by filament winding or contact molding;
• tanks that contain aggressive chemicals at atmospheric pressure, as classified in the standard;
• tanks made of a commercial-grade polyester or vinyl ester resin.

It includes requirements for materials, properties, design, construction, dimensions, tolerances, workmanship and appearance.

The standard does not cover:

• vessels for pressure above atmospheric or under vacuum, except as classified in the standard;
• vessels for liquids heated above their flash points.

It also calls for special design consideration for tanks subject to seismic, wind, ice, agitation or fluid dynamic forces, for service temperatures above 180 °F (82 °C), and for tanks with unsupported bottoms. If any of these apply to your tank, say so in the inquiry. A tank on a flat, fully supported pad at ambient temperature is the simplest case. A tank on legs, outdoors in a high-wind zone, or with an agitator needs more design work.

The values in ASTM D3299 are stated in inch-pound units. SI values in parentheses are for information. If your drawings are metric, agree the conversion basis with the supplier.

What changed in 2026

Before 2026, ASTM had two tank specifications: D3299 for filament-wound tanks and D4097 for contact-molded tanks. Subcommittee D20.23 rolled the contact-molded content of D4097-19 into D3299 and then withdrew D4097. Standards catalogs now list D3299-26 as superseding both D3299-24 and D4097-19.

For buyers this has three practical effects:

1. New specifications should cite ASTM D3299-26 for both filament-wound and contact-molded atmospheric tanks.
2. Old specifications that cite D4097 still describe a real product, but the document is withdrawn. Update the reference when you reissue the specification.
3. Ask how the tank is made. One standard now covers both processes, so the manufacturing method should be stated on the drawing or data sheet.

ASTM D4097: the withdrawn contact-molded standard

ASTM D4097 covered cylindrical tanks fabricated by contact molding, meaning hand lay-up or spray-up, for above-ground vertical installation and aggressive chemicals at atmospheric pressure. D4097-19 classified tanks by type, according to operating pressure or vacuum and the safety factor for external pressure, and by grade, according to the generic resin type. It listed reinforcements such as chopped-strand mat, woven roving, non-woven fabrics and surface mat, and it set design requirements for the shell, heads, joints, fittings and lugs.

You will still see D4097 on many drawings, data sheets and inspection plans. That is normal for a standard that was current for decades. When you see it now, treat it as a prompt to check whether the project should move to D3299-26.

ASME RTP-1: the full code for critical service

ASME RTP-1, Reinforced Thermoset Plastic Corrosion-Resistant Equipment, is a much larger document than D3299. The current edition is RTP-1–2025, issued on 31 October 2025, and ASME lists the next edition for 2027. It applies to stationary vessels used for the storage, accumulation or processing of corrosive or other substances at pressures not exceeding 15 psig (103 kPa gauge) external and/or 15 psig internal above any hydrostatic head.

RTP-1 adapts the principles of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, wherever they apply to reinforced plastics. It contains mandatory requirements, prohibitions and guidance for materials, design, fabrication, examination, inspection, testing, certification and pressure relief.

What sets RTP-1 apart is the certification system:

• ASME runs an RTP certification program that certifies a fabricator's quality control system to RTP-1.
• The program requires fabrication by hand lay-up and also allows spray-up and filament winding.
• Vessels from a certified fabricator can carry the ASME Certification Mark with the RTP designator.
• Vessels can also be registered with the National Board of Boiler and Pressure Vessel Inspectors by filing the fabricator's data report.

RTP-1 also expects the owner or user to define the service in a written User's Basis Requirements Specification (UBRS): the contents, temperature, pressure, loads and other design conditions.

When should you specify RTP-1 rather than D3299?

• The tank operates under positive pressure or vacuum within the 15 psig range.
• The contents are hazardous, and a failure would be serious.
• The owner's engineering standards require an ASME-marked vessel.
• The tank is a process vessel, such as a reactor, a scrubber sump or a vessel with an agitator, rather than simple storage.

Not every buyer needs RTP-1. For an atmospheric tank storing a dilute chemical on a fully supported pad, D3299 is usually enough. Ask your engineer, because RTP-1 adds cost through design documentation, inspection and certification.

Note on FIBROVX and RTP-1: FIBROVX can build tanks to the design and laminate requirements of a specification you provide, including one based on ASME RTP-1. Building to RTP-1 rules is not the same as supplying a vessel with the ASME Certification Mark, which only an ASME-certified fabricator can apply. If your project requires an ASME-marked vessel, tell us at inquiry so we can confirm clearly what we can supply.

EN 13121: the European route

In Europe, GRP tanks are usually designed to EN 13121, GRP tanks and vessels for use above ground. It has four parts: raw materials (part 1), composite materials and chemical resistance (part 2), design and workmanship (part 3), and delivery, installation and maintenance (part 4).

EN 13121-3 gives requirements for the design, fabrication, inspection, testing and verification of GRP tanks and vessels, with or without a thermoplastic lining, factory made or site built, non-pressurized or pressurized up to 10 bar, for temperatures between -40 °C and 120 °C. In the UK, BS EN 13121-3:2016 superseded the older BS 4994:1987, which is withdrawn. CEN approved a revised edition, EN 13121-3:2026, in 2026, so check which edition your contract cites.

EN 13121-3 does not apply to transport tanks, underground tanks, spherical or irregular vessels, or one-piece and sectional cisterns for cold water, which are covered by EN 13280.

Supporting test standards you will see

Tank specifications often cite these test and laminate documents:

All of these are current ASTM documents. Ask your supplier which ones they test to and how often.

How to choose: a simple decision path

1. Is the project in Europe or does it cite EN standards? Use EN 13121, or EN 13280 for a cold water cistern.
2. Does the tank run under pressure or vacuum, or must it carry an ASME mark? Use ASME RTP-1, within its 15 psig limit.
3. Is it an above-ground vertical tank at atmospheric pressure? Use ASTM D3299-26, for both filament-wound and contact-molded construction.
4. Is it horizontal, underground, rectangular or irregular? None of the documents above fits exactly. Write a project specification and state which clauses of D3299, RTP-1 or EN 13121 apply.
5. Check special conditions. Temperature above 82 °C, agitation, wind, seismic loads, legs or an unsupported bottom all need extra design work under every standard.

What else your tank specification should state

The standard is only the start. A complete FRP tank specification also states:

• Contents: chemical name, concentration, specific gravity, temperature range.
• Volume and dimensions: nominal capacity, diameter, straight-side height, head types.
• Resin: corrosion barrier resin and structural resin. Our resin guide compares the options.
• Corrosion barrier: surface veil and minimum thickness.
• Nozzles: size, flange standard, orientation and projection.
• Accessories: ladder, manway, level gauge, vent, hold-down lugs, lifting lugs.
• Site loads: wind, seismic and snow, and whether the tank is indoors or outdoors.
• Documents: drawings for approval, laminate schedule, test reports, inspection plan.

For chemical selection, start with our FRP chemical resistance guide. For a worked example of a demanding service, see FRP tanks for hydrochloric acid.

How FIBROVX can help

FIBROVX makes FRP water tanks, FRP hydrochloric acid tanks and other filament-wound FRP products in our own factory. Every tank is built to order: diameter, height, resin system, corrosion barrier, nozzles, manways, color and accessories can all be customized. Tell us which standard governs your project and the service conditions, and we will propose a laminate and design that meets it, with the drawings and test records we can provide. We do not claim certifications we do not hold.

Browse the range in Tanks, Pipes & Covers, or read the FRP storage tanks guide for an overview.

Common mistakes

• Citing D4097 on a new specification. It was withdrawn in 2026. Cite D3299-26.
• Using D3299 for a pressurized vessel. D3299 covers atmospheric tanks except as classified. Use RTP-1 or EN 13121 for real pressure or vacuum.
• Asking for "ASME RTP-1" without asking for the mark. Building to the rules and supplying a certified, marked vessel are different things. Say which one you need.
• Leaving out temperature. Service above 82 °C needs special design consideration under D3299.
• No contents data. Without the chemical, concentration and temperature, nobody can choose the resin.

Key terms

• Filament winding: a process where resin-wet continuous glass strands are wound onto a rotating mandrel.
• Contact molding: hand lay-up or spray-up of resin and glass on an open mold.
• Corrosion barrier: the resin-rich inner layers, usually with a surface veil, that face the chemical.
• Barcol hardness: an indentation hardness reading used to check that the resin has cured.
• UBRS: User's Basis Requirements Specification, the owner's statement of design conditions under ASME RTP-1.

Larger than a truck: field-wound tanks

Shop-built tanks are limited by road transport. Above that, tanks are wound on site: field-wound FRP storage tanks run from DN4000 to DN25000 with capacities up to 5,000 m³ per tank, on a reinforced-concrete foundation prepared to our drawing. See field-wound FRP tanks for large storage.

Watch: Large FRP Tanks & Standards in 27 Seconds

FAQ

Is ASTM D4097 still valid?

No. ASTM withdrew D4097 in 2026. Its contact-molded tank content is now part of ASTM D3299-26.

What is the difference between ASTM D3299 and ASME RTP-1?

ASTM D3299 is a product specification for atmospheric above-ground vertical tanks. ASME RTP-1 is a fuller code for stationary vessels up to 15 psig internal or external pressure, with a fabricator certification program and an optional ASME mark.

What pressure does ASME RTP-1 cover?

Up to 15 psig (103 kPa gauge) internal and/or 15 psig external, above any hydrostatic head.

Which standard applies to GRP tanks in Europe?

EN 13121, especially EN 13121-3 for design and workmanship, up to 10 bar and from -40 °C to 120 °C. Cold water cisterns are covered by EN 13280.

Does BS 4994 still apply?

BS 4994:1987 is withdrawn. It was superseded by BS EN 13121-3.

Related guides

• FRP Storage Tanks Guide
• FRP Tanks for Hydrochloric Acid
• FRP Chemical Resistance Guide
• Polyester vs Vinyl Ester vs Phenolic Resin
• Industries we serve
• FRP Quality Control: Barcol Hardness, Glass Content and Traceability
• Green Hydrogen Plants: FRP Tanks, Pipes, Scrubbers and Grating by Zone

Sources

• ASTM D3299-26, Glass-Fiber-Reinforced Thermoset Resin Corrosion-Resistant Tanks (scope; supersedes D4097): https://standards.nimonik.com/products/astm/d3299/
• ASTM D4097-19, Contact-Molded Glass-Fiber-Reinforced Thermoset Resin Corrosion-Resistant Tanks (withdrawn 2026): https://www.standards.nimonik.com/products/astm/d4097/
• ASME, RTP-1 Reinforced Thermoset Plastic Corrosion-Resistant Equipment: https://www.asme.org/codes-standards/find-codes-standards/reinforced-thermoset-plastic-corrosion-resistant-equipment
• ASME, RTP Corrosion-Resistant Equipment Certification: https://www.asme.org/certification-accreditation/reinforced-thermoset-plastic-corrosionresistant
• BSI Knowledge, BS EN 13121-3:2016 (supersedes BS 4994:1987): https://knowledge.bsigroup.com/products/grp-tanks-and-vessels-for-use-above-ground-design-and-workmanship-1
• iTeh Standards, EN 13121-3:2026 scope: https://standards.iteh.ai/catalog/standards/cen/6677e00a-c50f-4da6-b0cb-68584fee094f/en-13121-3-2026
• ASTM C582-23, Contact-Molded RTP Laminates for Corrosion-Resistant Equipment: https://standards.nimonik.com/products/astm/c582/
• ASTM D2583-25, Barcol hardness of rigid plastics: https://standards.nimonik.com/products/astm/d2583/
• ASTM D2563-26, Classifying visual defects in glass-reinforced plastic laminate parts: https://standards.nimonik.com/products/astm/d2563/