How to Check if a Gas Cylinder Needs Hydrostatic Testing

Gas cylinders are used every day in welding, fabrication, industrial manufacturing, beverage service, and specialty gas applications. To protect people, equipment, and facilities, cylinders must remain within their required hydrostatic test date.

This guide explains how to check if a gas cylinder needs hydrostatic testing and outlines Phoenix Welding Supply’s official hydro testing policy across all Arizona locations, including Phoenix, Mesa, Deer Valley, Tucson, Flagstaff, and Sierra Vista.

Where to Find the Hydrostatic Test Date on a Gas Cylinder

Every high pressure gas cylinder has permanent markings stamped into the metal near the shoulder or neck of the cylinder. These markings include the last hydrostatic test date and the DOT cylinder specification.

The hydrostatic test date is stamped as a month and year. For example, a marking of 06 21 indicates the cylinder was last tested in June 2021.

Stickers or labels may be present on the cylinder, but the stamped date is the official reference used for DOT compliance and safety inspections.

How Often Gas Cylinders Require Hydrostatic Testing

Hydrostatic testing intervals depend on the cylinder type and DOT specification. Most industrial gas cylinders follow these standards:

• Steel cylinders (DOT-3AA): every 5 years
• Aluminum cylinders (DOT-3AL): every 5 years
• Specialty or composite cylinders: often every 3 years or less

To determine if a cylinder is out of date, add the required retest interval to the stamped hydrostatic test date and compare it to today’s date.

Visual Damage Can Also Make a Cylinder Unsafe

Even if a cylinder is within its hydrostatic test date, it may still be unsafe to fill or exchange. Cylinders should not be filled if they show signs of:

• Heavy rust or corrosion
• Deep dents, bulges, or fire damage
• Missing or illegible stamped markings
• Unauthorized welding, grinding, or modifications
• Damaged or non compliant valves

Safety inspections are just as important as test dates.

Phoenix Welding Supply Hydrostatic Testing Policy

Phoenix Welding Supply follows a clear and consistent policy to ensure safety, regulatory compliance, and transparency for our customers across all Arizona locations.

Hydrostatic Test Fee: $48 per cylinder

1. If a customer brings in an out of date cylinder, or Phoenix Welding Supply picks up an out of date cylinder, the $48 hydrostatic test fee applies.
2. If the cylinder has a Phoenix Welding Supply sticker and the last hydrostatic test was completed within the past 12 months, Phoenix Welding Supply will cover the hydrostatic test cost.
3. If the cylinder has a Phoenix Welding Supply sticker and it has been more than 12 months since the last hydrostatic test, the $48 hydrostatic test fee will be charged to the customer.

If there is ever a question about a cylinder’s status, our team is happy to review the cylinder and explain the next steps.

What to Do if Your Cylinder Is Out of Date

If a gas cylinder is out of date or shows visible damage:

• Do not attempt to fill the cylinder
• Bring it to your nearest Phoenix Welding Supply location
• Our team will inspect the cylinder and guide you through testing or exchange options

Why Hydrostatic Testing Matters

Hydrostatic testing confirms that a cylinder can safely contain pressure without failure. Staying within required test dates helps protect workers, equipment, and job sites while ensuring compliance with DOT regulations.

Phoenix Welding Supply provides hydrostatic testing support and cylinder services at all locations throughout Arizona.

Phoenix Welding Supply Locations

• Phoenix Welding Supply – Phoenix, AZ
• Phoenix Welding Supply – Mesa, AZ
• Phoenix Welding Supply – Deer Valley, AZ
• Phoenix Welding Supply – Tucson, AZ
• Phoenix Welding Supply – Flagstaff, AZ
• Phoenix Welding Supply – Sierra Vista, AZ

To find the nearest branch, visit our
Locations page.

Frequently Asked Questions

What is hydrostatic testing for gas cylinders?

Hydrostatic testing is a pressure test that verifies a gas cylinder can safely hold compressed gas without leaking or rupturing.

How do I know if my gas cylinder is out of date?

Check the stamped hydrostatic test date on the cylinder neck and compare it to the required retest interval based on the DOT specification.

How much does hydrostatic testing cost at Phoenix Welding Supply?

The hydrostatic test fee is $48 per cylinder unless the cylinder qualifies under Phoenix Welding Supply’s sticker policy.

Can Phoenix Welding Supply inspect my cylinder?

Yes. Our team can inspect cylinders, explain test dates, and help determine whether hydrostatic testing or exchange is required.