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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
    (62)
    $43.12 each
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    388
    Thu, Aug 5
    388
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    388 Thu, Aug 5
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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)
    $57.75 each
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    264
    Thu, Aug 5
    264
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    264 Thu, Aug 5
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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)
    $40.34 each
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    340
    Thu, Aug 5
    340
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    340 Thu, Aug 5
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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)
    $1,129.95 each
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    29
    Mon, Aug 9 – Wed, Aug 11
    29
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    29 Mon, Aug 9 – Wed, Aug 11
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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)
    $1,049.99 each
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    20
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    20 Thu, Aug 5
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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)
    $179.95 each
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    Wed, Sep 1 – Thu, Sep 30
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    Wed, Sep 1 – Thu, Sep 30
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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
    $38.99 each
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    217
    Thu, Aug 5
    217
    QtyArrives
    217 Thu, Aug 5
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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)
    $1,639.95 each
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    5
    Mon, Aug 9 – Wed, Aug 11
    5
    QtyArrives
    5 Mon, Aug 9 – Wed, Aug 11
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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)
    $31.02 each
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    217
    Thu, Aug 5
    217
    QtyArrives
    217 Thu, Aug 5
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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
    $312.81 each
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    2
    Thu, Aug 5
    2
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    2 Thu, Aug 5
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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)
    $199.78 each
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    14
    Thu, Aug 5
    14
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    14 Thu, Aug 5
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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)
    $234.29 each
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    40
    Thu, Aug 5
    40
    QtyArrives
    40 Thu, Aug 5
    Questions? Call 1-888-757-4774
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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
    $573.10 each
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    Wed, Sep 1 – Thu, Sep 30
    Arrives
    Wed, Sep 1 – Thu, Sep 30
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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)
    $45.30 each
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    Wed, Sep 1 – Thu, Sep 30
    Arrives
    Wed, Sep 1 – Thu, Sep 30
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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
    $1,931.74 each
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    Tue, Sep 7 – Thu, Oct 7
    Arrives
    Tue, Sep 7 – Thu, Oct 7
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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)
    $26.48 each
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    43
    Thu, Aug 5
    43
    QtyArrives
    43 Thu, Aug 5
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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)
    $17.88 each
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    1,139
    Thu, Aug 5
    1,139
    QtyArrives
    1,139 Thu, Aug 5
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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)
    $40.95 each
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    356
    Thu, Aug 5
    356
    QtyArrives
    356 Thu, Aug 5
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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)
    $30.95 each
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    196
    Thu, Aug 5
    196
    QtyArrives
    196 Thu, Aug 5
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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
    (1)
    $25.78 each
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    9
    Thu, Aug 5
    235
    QtyArrives
    9 Thu, Aug 5
    226 Mon, Aug 9 – Tue, Aug 10
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  • Expansion Tank Support Kit w/ 32.5" Band for 2 Gallon Tanks Product Image
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    Expansion Tank Support Kit w/ 32.5" Band for 2 Gallon Tanks 598-0210 Expansion Tank Support Kit w/ 32.5" Band for 2 Gallon Tanks
    SKU: 598-0210 Sioux Chief
    SKU: 598-0210
    Brand: Sioux Chief
    (7)
    $4.71 each
      Box Up & Save 4%  
    $45.00 box of 10
    $4.50 each
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    541
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    541 Thu, Aug 5
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  • PLT-12, 4.5 Gallon<br>Potable Water Expansion Tank Product Image
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    PLT-12, 4.5 Gallon Potable Water Expansion Tank 0067371 PLT-12, 4.5 Gallon Potable Water Expansion Tank
    SKU: 0067371 Watts
    SKU: 0067371
    Brand: Watts
    $64.04 each
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    92
    Thu, Aug 5
    92
    QtyArrives
    92 Thu, Aug 5
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  • Expansion Tank Support Kit w/ 45" Band for 5 Gallon Tanks Product Image
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    Expansion Tank Support Kit w/ 45" Band for 5 Gallon Tanks 598-0213 Expansion Tank Support Kit w/ 45" Band for 5 Gallon Tanks
    SKU: 598-0213 Sioux Chief
    SKU: 598-0213
    Brand: Sioux Chief
    (1)
    $5.19 each
      Box Up & Save 8%  
    $47.70 box of 10
    $4.77 each
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    78
    Thu, Aug 5
    78
    QtyArrives
    78 Thu, Aug 5
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  • Nexus Flexconsole - 3/4" x 1/2" NPT - Stainless Steel (White) Product Image
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    Nexus Flexconsole - 3/4" x 1/2" NPT - Stainless Steel (White) F97976 Nexus Flexconsole - 3/4" x 1/2" NPT - Stainless Steel (White)
    SKU: F97976 Flamco
    SKU: F97976
    Brand: Flamco
    $68.29 each
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    89
    Thu, Aug 5
    89
    QtyArrives
    89 Thu, Aug 5
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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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