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  • THERM-X-TROL ST-5 Expansion Tank Product Image
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    THERM-X-TROL ST-5 Expansion Tank 140N43 THERM-X-TROL ST-5 Expansion Tank
    SKU: 140N43 Amtrol
    SKU: 140N43
    Brand: Amtrol
    (63)
    $48.00 each
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    672
    Mon, Nov 8
    672
    QtyArrives
    672 Mon, Nov 8
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  • THERM-X-TROL ST-12 Expansion Tank Product Image
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    THERM-X-TROL ST-12 Expansion Tank 141N43 THERM-X-TROL ST-12 Expansion Tank
    SKU: 141N43 Amtrol
    SKU: 141N43
    Brand: Amtrol
    (52)
    $57.72 each
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    7
    Mon, Nov 8
    7
    QtyArrives
    7 Mon, Nov 8
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  • PLT-5, 2.1 Gallon Potable<br>Water Expansion Tank Product Image
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    PLT-5, 2.1 Gallon Potable Water Expansion Tank 0067370 PLT-5, 2.1 Gallon Potable Water Expansion Tank
    SKU: 0067370 Watts
    SKU: 0067370
    Brand: Watts
    (15)
    $44.37 each
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    5
    Mon, Nov 8
    5
    QtyArrives
    5 Mon, Nov 8
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  • RP-15HP, 20 Gal<br>Residential Pressuriser Product Image
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    RP-15HP, 20 Gal Residential Pressuriser 2201-39 RP-15HP, 20 Gal Residential Pressuriser
    SKU: 2201-39 Amtrol
    SKU: 2201-39
    Brand: Amtrol
    (12)
    $1,362.05 each
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    11
    Thu, Nov 11 – Mon, Nov 15
    11
    QtyArrives
    11 Thu, Nov 11 – Mon, Nov 15
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  • RP-10HP, 14 Gal<br>Residential Pressuriser Product Image
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    RP-10HP, 14 Gal Residential Pressuriser 2201-37 RP-10HP, 14 Gal Residential Pressuriser
    SKU: 2201-37 Amtrol
    SKU: 2201-37
    Brand: Amtrol
    (11)
    $1,259.99 each
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    38
    Thu, Nov 11 – Mon, Nov 15
    38
    QtyArrives
    38 Thu, Nov 11 – Mon, Nov 15
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  • THERM-X-TROL ST-25V Expansion Tank<br>(10.3 Gallon) Product Image
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    THERM-X-TROL ST-25V Expansion Tank (10.3 Gallon) 143N164 THERM-X-TROL ST-25V Expansion Tank (10.3 Gallon)
    SKU: 143N164 Amtrol
    SKU: 143N164
    Brand: Amtrol
    (7)
    $171.34 each
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    19
    Mon, Nov 8
    19
    QtyArrives
    19 Mon, Nov 8
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  • 20 Gallon Well Expansion Tank (Stand) Product Image
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    20 Gallon Well Expansion Tank (Stand) EXW20V 20 Gallon Well Expansion Tank (Stand)
    SKU: EXW20V Bluefin
    SKU: EXW20V
    Brand: Bluefin
    $217.99 each
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    60
    Mon, Nov 8
    60
    QtyArrives
    60 Mon, Nov 8
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  • 2 Gallon Expansion Tank Product Image
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    2 Gallon Expansion Tank EX2 2 Gallon Expansion Tank
    SKU: EX2 Bluefin
    SKU: EX2
    Brand: Bluefin
    $41.39 each
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    777
    Mon, Nov 8
    777
    QtyArrives
    777 Mon, Nov 8
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  • 10.3 Gallon Vertical Expansion Tank Product Image
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    10.3 Gallon Vertical Expansion Tank EX10V 10.3 Gallon Vertical Expansion Tank
    SKU: EX10V Bluefin
    SKU: EX10V
    Brand: Bluefin
    $139.99 each
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    67
    Mon, Nov 8
    67
    QtyArrives
    67 Mon, Nov 8
    Questions? Call 1-888-757-4774
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  • 4.4 Gallon Expansion Tank Product Image
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    4.4 Gallon Expansion Tank EX4 4.4 Gallon Expansion Tank
    SKU: EX4 Bluefin
    SKU: EX4
    Brand: Bluefin
    $44.59 each
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    916
    Mon, Nov 8
    916
    QtyArrives
    916 Mon, Nov 8
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  • 3.2 Gallon Expansion Tank Product Image
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    3.2 Gallon Expansion Tank EX3 3.2 Gallon Expansion Tank
    SKU: EX3 Bluefin
    SKU: EX3
    Brand: Bluefin
    $45.99 each
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    38
    Mon, Nov 8
    38
    QtyArrives
    38 Mon, Nov 8
    Questions? Call 1-888-757-4774
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  • RP-25HP, 34 Gal<br>Residential Pressuriser Product Image
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    RP-25HP, 34 Gal Residential Pressuriser 2201-28 RP-25HP, 34 Gal Residential Pressuriser
    SKU: 2201-28 Amtrol
    SKU: 2201-28
    Brand: Amtrol
    (1)
    $2,170.29 each
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    Mon, Dec 13 – Thu, Jan 13
    Arrives
    Mon, Dec 13 – Thu, Jan 13
    Questions? Call 1-888-757-4774 or LiveChat Img Chat Us
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  • THERM-X-SPAN T-5 Expansion Tank<br>(2 Gallon) Product Image
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    THERM-X-SPAN T-5 Expansion Tank (2 Gallon) 140735 THERM-X-SPAN T-5 Expansion Tank (2 Gallon)
    SKU: 140735 Amtrol
    SKU: 140735
    Brand: Amtrol
    (20)
    $44.88 each
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    Tue, Dec 7 – Thu, Jan 6
    Arrives
    Tue, Dec 7 – Thu, Jan 6
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  • THERM-X-TROL ST-60V Expansion Tank<br>(34 Gallon) Product Image
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    THERM-X-TROL ST-60V Expansion Tank (34 Gallon) 147N130 THERM-X-TROL ST-60V Expansion Tank (34 Gallon)
    SKU: 147N130 Amtrol
    SKU: 147N130
    Brand: Amtrol
    $462.04 each
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    Tue, Dec 7 – Thu, Jan 6
    Arrives
    Tue, Dec 7 – Thu, Jan 6
    Questions? Call 1-888-757-4774 or LiveChat Img Chat Us
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  • THERM-X-TROL ST-30V Expansion Tank<br>(14 Gallon) Product Image
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    THERM-X-TROL ST-30V Expansion Tank (14 Gallon) 143N273 THERM-X-TROL ST-30V Expansion Tank (14 Gallon)
    SKU: 143N273 Amtrol
    SKU: 143N273
    Brand: Amtrol
    (7)
    $285.07 each
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    5
    Mon, Nov 8
    5
    QtyArrives
    5 Mon, Nov 8
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  • THERM-X-TROL ST-42V Expansion Tank<br>(20 Gallon) Product Image
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    THERM-X-TROL ST-42V Expansion Tank (20 Gallon) 144N177 THERM-X-TROL ST-42V Expansion Tank (20 Gallon)
    SKU: 144N177 Amtrol
    SKU: 144N177
    Brand: Amtrol
    (1)
    $332.93 each
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    Tue, Dec 7 – Thu, Jan 6
    Arrives
    Tue, Dec 7 – Thu, Jan 6
    Questions? Call 1-888-757-4774 or LiveChat Img Chat Us
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  • THERM-X-TROL ST-80V Expansion Tank<br>(44 Gallon) Product Image
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    THERM-X-TROL ST-80V Expansion Tank (44 Gallon) 147N131 THERM-X-TROL ST-80V Expansion Tank (44 Gallon)
    SKU: 147N131 Amtrol
    SKU: 147N131
    Brand: Amtrol
    $685.78 each
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    Tue, Dec 7 – Thu, Jan 6
    Arrives
    Tue, Dec 7 – Thu, Jan 6
    Questions? Call 1-888-757-4774 or LiveChat Img Chat Us
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  • THERM-X-SPAN T-12 Expansion Tank<br>(4.4 Gallon) Product Image
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    THERM-X-SPAN T-12 Expansion Tank (4.4 Gallon) 141363 THERM-X-SPAN T-12 Expansion Tank (4.4 Gallon)
    SKU: 141363 Amtrol
    SKU: 141363
    Brand: Amtrol
    (3)
    $51.22 each
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    Tue, Dec 7 – Thu, Jan 6
    Arrives
    Tue, Dec 7 – Thu, Jan 6
    Questions? Call 1-888-757-4774 or LiveChat Img Chat Us
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  • THERM-X-TROL ASME<br>ST-30V-C Expansion Tank Product Image
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    THERM-X-TROL ASME ST-30V-C Expansion Tank 143-218 THERM-X-TROL ASME ST-30V-C Expansion Tank
    SKU: 143-218 Amtrol
    SKU: 143-218
    Brand: Amtrol
    $2,190.08 each
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    Mon, Dec 13 – Thu, Jan 13
    Arrives
    Mon, Dec 13 – Thu, Jan 13
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  • THERM-X-TROL ST-1 Expansion Tank (Matte Tan) Product Image
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    THERM-X-TROL ST-1 Expansion Tank (Matte Tan) 140P01 THERM-X-TROL ST-1 Expansion Tank (Matte Tan)
    SKU: 140P01 Amtrol
    SKU: 140P01
    Brand: Amtrol
    (1)
    $28.98 each
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    18
    Mon, Nov 8
    18
    QtyArrives
    18 Mon, Nov 8
    Questions? Call 1-888-757-4774
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  • QuickStrap Expansion Tank Mounting Bracket <br>(5 Gal. Capacity) Product Image
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    QuickStrap Expansion Tank Mounting Bracket (5 Gal. Capacity) QS-U QuickStrap Expansion Tank Mounting Bracket (5 Gal. Capacity)
    SKU: QS-U Holdrite
    SKU: QS-U
    Brand: Holdrite
    (6)
    $16.77 each
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    828
    Mon, Nov 8
    828
    QtyArrives
    828 Mon, Nov 8
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  • 11" HydroClaw Expansion Tank Support Bracket Product Image
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    11" HydroClaw Expansion Tank Support Bracket HC11-A 11" HydroClaw Expansion Tank Support Bracket
    SKU: HC11-A Storm King Enterprises
    SKU: HC11-A
    Brand: Storm King Enterprises
    (53)
    $45.38 each
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    46
    Mon, Nov 8
    46
    QtyArrives
    46 Mon, Nov 8
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  • 8" HydroClaw Expansion Tank Support Bracket Product Image
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    8" HydroClaw Expansion Tank Support Bracket HC8-B 8" HydroClaw Expansion Tank Support Bracket
    SKU: HC8-B Storm King Enterprises
    SKU: HC8-B
    Brand: Storm King Enterprises
    (32)
    $35.70 each
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    Added to List Icon List
    340
    Mon, Nov 8
    340
    QtyArrives
    340 Mon, Nov 8
    Questions? Call 1-888-757-4774
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  • ZEP-1 Stainless Steel Thermal Expansion Tank Product Image
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    ZEP-1 Stainless Steel Thermal Expansion Tank ZEP-1 ZEP-1 Stainless Steel Thermal Expansion Tank
    SKU: ZEP-1 Zilmet
    SKU: ZEP-1
    Brand: Zilmet
    (2)
    $25.79 each
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    95
    Wed, Nov 10 – Thu, Nov 11
    95
    QtyArrives
    95 Wed, Nov 10 – Thu, Nov 11
    Questions? Call 1-888-757-4774
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FAQs, Manuals & Videos

Resources

Videos

Articles

  • 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 Size Calculator located here.

    We offer a wide selection of
    Therm-X-Trol and Well-X-Trol expansion tanks to suit all of your plumbing and heating needs.
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