Expansion Tanks

To determine the size needed for your system, use this quick and convenient Expansion Tank Size Calculator.

Extrol tanks manufactured by Amtrol are ideal for hydronic heating systems. The Watts ET series expansion tanks are designed for closed radiant heat and hydronic heating systems. These tanks are not designed for potable water open systems. For these systems, go to Therm-X-Trol tanks under plumbing supplies.

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  • #15 Extrol Expansion Tank (2 Gallon Volume) View Specs
    • SKU: 101-1
    • Brand: Amtrol

    $23.25 / each

    $89.40 / box
    4 x $22.35

    In Stock! (466 Available) Ships in 24-48 Hrs
  • #30 Extrol Expansion Tank (4.4 Gallon Volume) View Specs
    • SKU: 102-1
    • Brand: Amtrol

    $28.55 / each

    $109.96 / box
    4 x $27.49

    In Stock! (1031 Available) Ships in 24-48 Hrs
  • #60 Extrol Expansion Tank (7.6 Gallon Volume) View Specs
    • SKU: 103-1
    • Brand: Amtrol

    $62.89 / each

    $243.80 / box
    4 x $60.95

    In Stock! (201 Available) Ships in 24-48 Hrs
  • #90 Extrol Expansion Tank (14 Gallon Volume) View Specs
    • SKU: 112-1
    • Brand: Amtrol

    $92.95 / each

    $359.80 / box
    4 x $89.95

    In Stock! (27 Available) Ships in 24-48 Hrs
  • SX-30V Extrol Expansion Tank (14 Gallon Volume) View Specs
    • SKU: 118-27
    • Brand: Amtrol

    $102.95 / each

    $296.55 / box
    3 x $98.85

    In Stock! (23 Available) Ships in 24-48 Hrs
  • SX-40V Extrol Expansion Tank (20 Gallon Volume) View Specs
    • SKU: 118-78
    • Brand: Amtrol

    $129.95 / each

    $377.85 / box
    3 x $125.95

    In Stock! (20 Available) Ships in 24-48 Hrs
  • SX-60V Extrol Expansion Tank (32 Gallon Volume) View Specs
    • SKU: 118-79
    • Brand: Amtrol

    $224.95 / each

    In Stock! (9 Available) Ships in 24-48 Hrs
  • SX-90V Extrol Expansion Tank (44 Gallon Volume) View Specs
    • SKU: 118-153
    • Brand: Amtrol

    $392.95 / each

    $759.90 / box
    2 x $379.95

    In Stock! (5 Available) Ships in 24-48 Hrs
  • SX-110V Extrol Expansion Tank (62 Gallon Volume) View Specs
    • SKU: 118-154
    • Brand: Amtrol

    $489.95 / each

    In Stock! (2 Available) Ships in 24-48 Hrs
  • SX-160V Extrol Expansion Tank (86 Gallon Volume) View Specs
    • SKU: 118-155
    • Brand: Amtrol

    $509.95 / each

    $989.90 / box
    2 x $494.95

    In Stock! (24 Available) Ships in 24-48 Hrs
  • AX-40 Extrol Expansion Tank (21.7 Gallon Volume) - Horizontal Model View Specs

    $1,629.95 / each

    Non-Stock Item Allow 1-2 Weeks to Ship Out
  • SX-130V Extrol Expansion Tank (81 Gallon Volume) View Specs
    • SKU: 149-165
    • Brand: Amtrol

    $599.95 / each

    Non-Stock Item Allow 1-2 Weeks to Ship Out
  • RX-15 Radiant Extrol Expansion Tank (2 Gallon Volume) View Specs

    $49.55 / each

    $191.80 / box
    4 x $47.95

    In Stock! (13 Available) Ships in 24-48 Hrs
  • RX-30 Radiant Extrol Expansion Tank (4.4 Gallon Volume) View Specs

    $60.95 / each

    $235.40 / box
    4 x $58.85

    In Stock! (68 Available) Ships in 24-48 Hrs
  • RX-60 Radiant Extrol Expansion Tank (10.3 Gallon Volume) View Specs

    $149.95 / each

    $434.85 / box
    3 x $144.95

    In Stock! (5 Available) Ships in 24-48 Hrs
  • ETX-15, 2.1 Gallon Non-Potable Water Expansion Tank View Specs

    $27.25 / each

    $262.50 / box
    10 x $26.25

    In Stock! (5 Available) Ships in 24-48 Hrs
  • ETX-30, 4.5 Gallon Non-Potable Water Expansion Tank View Specs

    $29.95 / each

    $289.50 / box
    10 x $28.95

    In Stock! (3 Available) Ships in 24-48 Hrs
  • ETX-60, 6.0 Gallon Non-Potable Water Expansion Tank View Specs

    $56.95 / each

    $274.75 / box
    5 x $54.95

    In Stock! (1 Available) Ships in 24-48 Hrs
  • ETX-90, 15 Gallon Non-Potable Water Expansion Tank View Specs

    $105.95 / each

    Non-Stock Item Allow 7-10 Days to Ship Out
  • 8" HydroClaw Expansion Tank Support Bracket View Specs
    • SKU: HC8-A
    • Brand: Storm King Enterprises

    $30.95 / each

    In Stock! (41 Available) Ships in 24-48 Hrs

More About Expansion Tanks

An expansion tank is designed to relieve pressure in both a potable water and closed heating system. An expansion tank ensures a constant pressure is maintained within the pipes so they do not get damaged from excess pressure.

An expansion tank has two parts which are divided by a rubber diaphragm. The top portion of the tank is connected to the hot water system and is filled with water. The bottom portion is filled with air set at approximately 12 psi. As the hot water system is turned on or off, pressure increases. As pressure increases, the diaphragm in the expansion tank is pushed down. This compresses the air in the tank, creating more space for excess water to enter. This relieves excess pressure in the system and prevents pipes in the system from being damaged.

In the event that the diaphragm fails, the tank will completely fill with water. If this occurs, the tank must be replaced immediately. To check if the expansion tank is working properly, simply place your hand on the tank and feel its temperature. The top portion of the tank should feel warm to the touch, and the bottom portion of the tank should be room temperature. If the entire tank is warm, it is likely that the tank has completely filled with hot water.

Expansion tanks have capacities ranging from 2 gallons to several hundred gallons. To determine the size needed for your system, use the Expansion Tank Sizing Calculator.

We offer a wide selection of Amtrol, Watts, Cash Acme, and Bell & Gossett expansion tanks to suit all of your plumbing and heating needs.