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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
    Brand: Amtrol
    (61)
    $39.00 each
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    (50)
    $46.00 each
    11
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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
    Brand: Watts
    (13)
    $38.42 each
    365
    Fri, May 28
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    365 Fri, May 28
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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
    Brand: Amtrol
    (12)
    $1,213.28 each
    Thu, Jul 1 – Tue, Aug 3
    Arrives
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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
    Brand: Amtrol
    (10)
    $1,049.99 each
    13
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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
    Brand: Bluefin
    $38.99 each
    452
    Fri, May 28
    452
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    452 Fri, May 28
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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
    Brand: Amtrol
    (7)
    $149.00 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    (1)
    $1,751.12 each
    Thu, Jul 1 – Tue, Aug 3
    Arrives
    Thu, Jul 1 – Tue, Aug 3
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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
    Brand: Amtrol
    (20)
    $36.67 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    $312.81 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    (7)
    $205.89 each
    22
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    22 Fri, May 28
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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
    Brand: Amtrol
    (1)
    $249.00 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    $505.56 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Amtrol
    (3)
    $42.71 each
    58
    Fri, May 28
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    58 Fri, May 28
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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
    Brand: Amtrol
    $1,774.99 each
    Thu, Jul 1 – Tue, Aug 3
    Arrives
    Thu, Jul 1 – Tue, Aug 3
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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
    Brand: Amtrol
    $26.48 each
    Mon, Jun 28 – Tue, Jul 27
    Arrives
    Mon, Jun 28 – Tue, Jul 27
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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
    Brand: Holdrite
    (6)
    $16.98 each
    683
    Fri, May 28
    683
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    683 Fri, May 28
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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
    Brand: Storm King Enterprises
    (53)
    $40.95 each
    34
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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
    Brand: Storm King Enterprises
    (32)
    $30.95 each
    202
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    202
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    202 Fri, May 28
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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
    Brand: Zilmet
    (1)
    $25.78 each
    149
    Fri, May 28
    155
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    149 Fri, May 28
    6 Wed, Jun 2 – Thu, Jun 3
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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
    Brand: Sioux Chief
    (7)
    $4.49 each
      Box Up & Save 4%  
    $42.90 box of 10
    $4.29 each
    553
    Fri, May 28
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    553 Fri, May 28
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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
    Brand: Watts
    $62.12 each
    61
    Fri, May 28
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    61 Fri, May 28
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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
    Brand: Sioux Chief
    (1)
    $4.99 each
      Box Up & Save 8%  
    $45.90 box of 10
    $4.59 each
    108
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    108 Fri, May 28
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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
    Brand: Flamco
    $68.29 each
    41
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    41 Fri, May 28
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FAQs, Manuals & Videos

Resources

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  • 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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