Expansion Tanks

Expansion tanks accommodate the added water volume created as water heats, helping manage system pressure in potable water supply, domestic hot-water, and closed-loop hydronic heating applications. Commercial buyers, plumbing professionals, contractors, and facility maintenance teams use them when specifying compatible heating equipment and water-system components.

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Helpful Buying Guide

How to Choose an Expansion Tank

Start with the water-system application, then compare capacity, connection type, pre-charge, and stated operating limits. This category includes tanks for potable water and domestic hot-water systems, as well as tanks for closed, non-potable hydronic heating systems.

Visual Guide

Popular examples in this category

4-Gallon Potable Water Expansion Tank4-Gallon Potable Water Expansion TankWBB21832942-Gallon Potable Water Expansion Tank2-Gallon Potable Water Expansion TankWBB21832959.2-Gallon Expansion Tank with 3/4-Inch MNPT Connection9.2-Gallon Expansion Tank with 3/4-Inch MNPT ConnectionWBB18774784.5-Gallon Expansion Tank with 3/4 in. MNPT Connection4.5-Gallon Expansion Tank with 3/4 in. MNPT ConnectionWBB1877457
Use Cases

Match the tank to the system water type

Potable water tanks are intended for potable water supply systems. A water heater expansion tank is for domestic hot-water systems. Hydronic and non-potable models are for closed-loop heating systems.

How to Choose

Compare the listed connection and capacity

Select a tank with the capacity required by the system specification and a compatible connection. Listed options include 1/2-inch NPT or MNPT and 3/4-inch NPT or MNPT connections.

Applications

Plan for pressure management

Potable and domestic hot-water tanks absorb water expanded during heating. Closed hydronic tanks receive expanding water as temperature rises to help control pressure buildup.

Additional Info

Review setup and service details

Available tanks list 12 PSI, 40 PSI, 50 PSI, or 12 PSIG pre-charge settings. Some non-potable models include a charging valve or standard tire valve for on-site charging.

2–9.2 gal.Listed capacity range

Compare capacities from 2 gallons through 9.2 gallons.

1/2 or 3/4 in.Connection sizes

Listed tank connections use 1/2-inch or 3/4-inch sizing.

12–50 PSIListed pre-charge settings

Available pre-charge settings include 12, 40, and 50 PSI.

75–150 PSIListed working-pressure range

Selected models list maximum working pressures from 75 PSI to 150 PSI.

Comparison Guide

Compare Expansion Tank Types

Use the system application and listed installation details to narrow the selection.

Product typeBest matched applicationKey listed selection factors
Potable water expansion tanksPotable water supply systems2- or 4-gallon capacity; 3/4-inch NPT connection; 40 PSI pre-charge
Hydronic and non-potable expansion tanksClosed-loop, non-potable hydronic heating systems2 to 8-gallon capacities; 1/2-inch NPT or MNPT connections; commonly listed 12 PSI pre-charge
Water heater expansion tankDomestic hot-water systems4.4-gallon capacity; 50 PSI precharge; antimicrobial liner, water diffuser, and stainless steel connection
Planning Guide

Plan the right fit before choosing

First, identify the application

Potable, domestic hot-water, and hydronic tanks serve different systems

Application is the primary selection point. Potable water expansion tanks provide expansion volume for potable water supply systems. The domestic hot-water option absorbs water expanded during water heating to help control pressure and reduce relief valve discharge. Hydronic and non-potable tanks are designed for closed-loop heating piping and systems.

  • Choose potable water models for potable water supply systems.
  • Choose the water heater model for domestic hot-water systems.
  • Choose hydronic or non-potable models for closed-loop, non-potable heating systems.
Then, match installation details

Confirm capacity, connection, and available space

Capacity options represented range from 2 gallons to 9.2 gallons. Connection choices include 1/2-inch and 3/4-inch fittings, with NPT and MNPT options. For installations with limited clearance, compare the listed dimensions where provided.

  • Capacities include 2, 2.1, 4, 4.4, 4.5, 6, 8, 9.2 gallons.
  • Connections include 1/2-inch NPT, 1/2-inch MNPT, 3/4-inch NPT, and 3/4-inch MNPT.
  • Listed dimensions are available on selected 4.5-gallon, 9.2-gallon, and isolation tee options.
Check operating information

Compare pre-charge and stated working limits

Several hydronic and non-potable tanks list a 12 PSI or 12 PSIG pre-charge, while potable water tanks list 40 PSI and the domestic hot-water option lists 50 PSI. Where maximum working pressure or maximum temperature is listed, verify that the system operates within that stated limit.

  • Listed maximum working pressures include 75 PSI, 100 PSI, and 150 PSI on selected models.
  • One 2-gallon potable tank lists a 200°F maximum temperature.
  • Membrane and diaphragm designs on selected non-potable tanks keep water separate from tank air.
FAQ

Common questions before buying

What is the difference between potable and non-potable expansion tanks?

Potable water tanks are for potable water supply systems. Non-potable and hydronic tanks are for closed-loop hydronic heating systems.

What capacities are available?

The represented tanks range from 2 gallons to 9.2 gallons, including 2.1-, 4-, 4.4-, 4.5-, 6-, and 8-gallon options.

Which connection types are listed?

Listed connections include 1/2-inch NPT, 1/2-inch MNPT, 3/4-inch NPT, and 3/4-inch MNPT, depending on the model.

What does the isolation tee do?

The expansion tank and fill valve isolation tee allows both the expansion tank and fill valve to be isolated through one tee assembly in a heating system.

Helpful Buying Guide

How to Choose an Expansion Tank

Start with the water-system application, then compare capacity, connection type, pre-charge, and stated operating limits. This category includes tanks for potable water and domestic hot-water systems, as well as tanks for closed, non-potable hydronic heating systems.

Visual Guide

Popular examples in this category

4-Gallon Potable Water Expansion Tank4-Gallon Potable Water Expansion TankWBB21832942-Gallon Potable Water Expansion Tank2-Gallon Potable Water Expansion TankWBB21832959.2-Gallon Expansion Tank with 3/4-Inch MNPT Connection9.2-Gallon Expansion Tank with 3/4-Inch MNPT ConnectionWBB18774784.5-Gallon Expansion Tank with 3/4 in. MNPT Connection4.5-Gallon Expansion Tank with 3/4 in. MNPT ConnectionWBB1877457
Use Cases

Match the tank to the system water type

Potable water tanks are intended for potable water supply systems. A water heater expansion tank is for domestic hot-water systems. Hydronic and non-potable models are for closed-loop heating systems.

How to Choose

Compare the listed connection and capacity

Select a tank with the capacity required by the system specification and a compatible connection. Listed options include 1/2-inch NPT or MNPT and 3/4-inch NPT or MNPT connections.

Applications

Plan for pressure management

Potable and domestic hot-water tanks absorb water expanded during heating. Closed hydronic tanks receive expanding water as temperature rises to help control pressure buildup.

Additional Info

Review setup and service details

Available tanks list 12 PSI, 40 PSI, 50 PSI, or 12 PSIG pre-charge settings. Some non-potable models include a charging valve or standard tire valve for on-site charging.

2–9.2 gal.Listed capacity range

Compare capacities from 2 gallons through 9.2 gallons.

1/2 or 3/4 in.Connection sizes

Listed tank connections use 1/2-inch or 3/4-inch sizing.

12–50 PSIListed pre-charge settings

Available pre-charge settings include 12, 40, and 50 PSI.

75–150 PSIListed working-pressure range

Selected models list maximum working pressures from 75 PSI to 150 PSI.

Comparison Guide

Compare Expansion Tank Types

Use the system application and listed installation details to narrow the selection.

Product typeBest matched applicationKey listed selection factors
Potable water expansion tanksPotable water supply systems2- or 4-gallon capacity; 3/4-inch NPT connection; 40 PSI pre-charge
Hydronic and non-potable expansion tanksClosed-loop, non-potable hydronic heating systems2 to 8-gallon capacities; 1/2-inch NPT or MNPT connections; commonly listed 12 PSI pre-charge
Water heater expansion tankDomestic hot-water systems4.4-gallon capacity; 50 PSI precharge; antimicrobial liner, water diffuser, and stainless steel connection
Planning Guide

Plan the right fit before choosing

First, identify the application

Potable, domestic hot-water, and hydronic tanks serve different systems

Application is the primary selection point. Potable water expansion tanks provide expansion volume for potable water supply systems. The domestic hot-water option absorbs water expanded during water heating to help control pressure and reduce relief valve discharge. Hydronic and non-potable tanks are designed for closed-loop heating piping and systems.

  • Choose potable water models for potable water supply systems.
  • Choose the water heater model for domestic hot-water systems.
  • Choose hydronic or non-potable models for closed-loop, non-potable heating systems.
Then, match installation details

Confirm capacity, connection, and available space

Capacity options represented range from 2 gallons to 9.2 gallons. Connection choices include 1/2-inch and 3/4-inch fittings, with NPT and MNPT options. For installations with limited clearance, compare the listed dimensions where provided.

  • Capacities include 2, 2.1, 4, 4.4, 4.5, 6, 8, 9.2 gallons.
  • Connections include 1/2-inch NPT, 1/2-inch MNPT, 3/4-inch NPT, and 3/4-inch MNPT.
  • Listed dimensions are available on selected 4.5-gallon, 9.2-gallon, and isolation tee options.
Check operating information

Compare pre-charge and stated working limits

Several hydronic and non-potable tanks list a 12 PSI or 12 PSIG pre-charge, while potable water tanks list 40 PSI and the domestic hot-water option lists 50 PSI. Where maximum working pressure or maximum temperature is listed, verify that the system operates within that stated limit.

  • Listed maximum working pressures include 75 PSI, 100 PSI, and 150 PSI on selected models.
  • One 2-gallon potable tank lists a 200°F maximum temperature.
  • Membrane and diaphragm designs on selected non-potable tanks keep water separate from tank air.
FAQ

Common questions before buying

What is the difference between potable and non-potable expansion tanks?

Potable water tanks are for potable water supply systems. Non-potable and hydronic tanks are for closed-loop hydronic heating systems.

What capacities are available?

The represented tanks range from 2 gallons to 9.2 gallons, including 2.1-, 4-, 4.4-, 4.5-, 6-, and 8-gallon options.

Which connection types are listed?

Listed connections include 1/2-inch NPT, 1/2-inch MNPT, 3/4-inch NPT, and 3/4-inch MNPT, depending on the model.

What does the isolation tee do?

The expansion tank and fill valve isolation tee allows both the expansion tank and fill valve to be isolated through one tee assembly in a heating system.

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