Armstrong Expansion Tanks

Armstrong Expansion Tanks for Pressure Stabilization

Information:

• Armstrong Series AET ASME Plain Steel Expansion Tank Operating Instructions
• Armstrong Series AET ASME Plain Steel Expansion Tank Submittal Sheet
• Armstrong Series AST ASME Hydro Pneumatic Drawdown Tank Operating Instructions
• Armstrong Series AST ASME Pre Charged Expansion Tank For Potable Water Submittal Sheet
• Armstrong Series AX-L ASME Expansion Tank Product Data Sheet
• Armstrong Series AX & AX-V ASME Pre Pressurized Expansion Tank Installation Operating Instructions
• Armstrong Series AX ASME Pre Charged Horizontal Expansion Tank Submittal Sheet
• Armstrong Series AX-V ASME Pre Charged Vertical Expansion Tank Submittal Sheet
• Armstrong Series L Bladder Expansion Tank Installation Operating Instructions
• Armstrong Series L ASME Pre Charged Expansion Tank Submittal Sheet
• Armstrong Series L High Pressure Hydronic Expansion Tank Submittal Sheet 35L TO 800L
• Armstrong Series L High Pressure Hydronic Expansion Tank Submittal Sheet 1000L TO 4000L
• Armstrong Series SX Diaphragm Expansion Tank Installation Operating Instructions
• Armstrong NON-ASME Diaphragm Expansion Tank Submittal Sheet
• Armstrong Series WX-L ASME Pre Charged Bladder Expansion Tank Installation Operating Instructions
• Armstrong Series WX-L ASME Pre Charged Bladder Expansion Tank Submittal Sheet

At National Pump Supply, we carry a wide selection of Armstrong expansion tanks built to manage pressure changes in water-based systems. These tanks are used in boiler rooms, chiller plants, and booster pump installations—anywhere pressure needs to stay stable and systems need to run safely.

Whether you're a contractor or facility manager, Armstrong’s tanks are a solid choice. They're reliable, easy to work with, and available in a variety of models, including diaphragm and bladder expansion tanks. Browse our collection today and pick the right fit for your system!

Engineered for Smaller Sizes and Stronger Performance

Armstrong expansion tanks are designed to reduce tank sizes by up to 80 percent compared to standard designs. That’s a big deal when space is tight or installation costs are a concern. The tanks use compressed air to maintain system pressure by accepting and releasing the changing volume of water as it heats and cools.

Inside, each tank features a diaphragm or bladder that separates the air from the water. This setup protects the system from pressure spikes and helps extend the life of pumps, valves, and piping. The air cushion is pre-charged at the factory, but it can be adjusted in the field to meet your system’s exact needs.

Trusted Armstrong Designs

We offer Armstrong tanks in several styles:

• AX Series – Pre-charged, ASME-rated diaphragm expansion tanks
• SX Series – Compact diaphragm tanks in various mounting options
• AST Series – ASME pre-pressurized expansion tanks
• A-Series – High-volume bladder tanks for larger commercial systems
• WX Series – Bladder tanks made for potable water use
• AET Models – AET plain steel expansion tanks for basic pressure applications

Each tank is built to handle pressure changes in a closed-loop system and is backed by Armstrong Fluid Technology’s reputation for quality.

Used in All the Right Places

Armstrong expansion tanks are used in a wide range of mechanical systems, including:

• Boiler systems
• Chiller plants
• Hydronic heating loops
• Potable water applications
• Booster installations

These tanks help maintain consistent pressure, reduce the risk of water hammer, and prevent wear on system parts. If you’re working on a new build or replacing an old tank, Armstrong has a solution that fits.

What to Expect From Our Inventory of Armstrong Expansion Tanks

Our warehouse is stocked with Armstrong models that handle a wide flow range—from smaller 15 GPM tanks to large-capacity options that support over 1,000 GPM.

Whether you're looking for a compact diaphragm tank for a light commercial setup or a high-volume bladder tank for a large facility, we have what you need.

Prices generally range between $100 and $11,000, depending on size, series, and performance. For the latest availability and lead times, contact our team for a fast quote.

Important Warranty and Shipping Info

Every water expansion tank includes a standard manufacturer’s warranty, but to stay covered, your system must be installed and operated following the manufacturer’s IOM guidelines.

Here are a few quick things to know:

• Startup, commissioning, and training services are not included. These are handled by the contractor or commissioning agent.
• Shipping is FOB point of origin, and standard ground service is used within the continental U.S.
• All sales are final, and any shipping damage must be reported directly to the carrier.

Need a rush order? We may be able to expedite it—just ask a member of our sales team.

Why Buy From National Pump Supply?

Our team knows pumps, tanks, and system pressure better than anyone in the business. We don’t just ship parts—we help you get the right product the first time. If you're unsure what size or type of Armstrong expansion tank is right for your job, we’re here to help.

Call us at 1-800-781-7405 or email Sales@NationalPumpSupply.com. We'll help you figure out the right fit and get your order moving—fast.