THERM-X-TROL ST-12 Expansion Tank Zoom

THERM-X-TROL ST-12 Expansion Tank

SKU:141N43

Brand: Amtrol

Amtrol
Qty Price
$57.95
/ each
$221.96 / box (4 units x $55.49)
In Stock! Ships in 24-48 Hours
(11 Available)
5

Specs

Tank Volume: 4.4 Gallons
Height (Inches): 15.5
Diameter (Inches): 11"
Weight (lbs): 9 lbs
Warranty: 5-Year Limited Warranty
Size: 3/4"
Material: Steel
Application: Plumbing
Max Pressure (PSI): 150 psi
Temperature Range (F): 200°F MAX

Description for Amtrol 141N43

Amtrol ST-12 (Therm-X-Trol) is a water heater expansion tank, designed for use in domestic hot water heating systems to eliminate the potential hazards of water expansion. Water heater expansion tank is commonly installed in a domestic hot water system that contains a backflow preventer, a check valve or a pressure reducing valve.

Amtrol ST-12 Advantages:

  • Eliminates the waste of energy and water, thus saving money
  • Protects the water heater and plumbing fixtures from premauture failure
  • Reduces potential safety hazards associated with thermal expansion
  • Prevents a dangerous pressure build-up in the system
  • Prevents the relief valve from going off
  • Therm-X-Trol brand is the #1 choice of Professional Installers

The HydroClaw Expansion Tank Support Bracket provides a safe and reliable option if you prefer to mount your expansion tank. This expansion tank bracket is easy to install and will hold any tank with a diameter of 11" nominal.

THERM-X-TROL ST-12 Expansion Tank

REVIEW SNAPSHOT®

by PowerReviews
AmtrolTHERM-X-TROL ST-12 Expansion Tank
 
4.9

(based on 16 reviews)

Ratings Distribution

  • 5 Stars

     

    (14)

  • 4 Stars

     

    (2)

  • 3 Stars

     

    (0)

  • 2 Stars

     

    (0)

  • 1 Stars

     

    (0)

100%

of respondents would recommend this to a friend.

Reviewed by 16 customers

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(0 of 1 customers found this review helpful)

 
5.0

As expected

By DementedDad

from Texas

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Works. Precharge was about 60lbs and I did not need to adjust that for my purpose. This is a fairly heavy tank so I mounted it to a wall with a strap to take the weight of it off the piping. Remains to be seen how long it will last...

 
5.0

Excellent Product

By John

from Reno

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

I have a 75 gallon residential gas hot water heater that was continuously discharging water from the pressure relief valve (150 lbs). By using the sizing of expansion tanks for this system, I found that the original expansion tank was undersized and not functional. The replacement with the proper sized new expansion tank and following the directions provided by the manufacturer, the the issue was resolved.

 
5.0

Professional Grade...Product..People

By Philisophe

from Ohio

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Expansion tanks failing ..replaced with
Amtrol...

Installed a water pressure regulator also
due to high incoming water pressure from utility
company..

Great product..Great People..arrived on time

 
5.0

Therm X trol works great

By Benny

from Cincinnati, OH

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Would do business again with this vendor

 
5.0

Reliable, well-made product

By Bend Bill

from Bend, OR

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Replaced 10 year old expansion tank and worked well as expected. Installation instructions could be more detailed.

(0 of 1 customers found this review helpful)

 
5.0

good product

By Dameem

from Austintown, Ohio

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Bought this to replace another expansion tank when I changed hot water tanks. Good product, does the job it's suppose to, no problems.

 
5.0

Simple

By Wheels

from Pawleys Island, SC

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Quick delivery. Easy to remove old item and install new. Instructions were clear!

 
5.0

ST -12 Replacement

By Plumb Krazy

from West suburbs of Chicago

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Easy to order ,fast shipper,simple to install!The install is a good coversation topic @ the holidays.Lotsa guys said I didn't know that!!!!

 
4.0

A bit expensive but does the job!

By dwdiy1

from San Diego, CA

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

Had to build a tee with a female and two male NPT connectors. I ended up placing it on a shelf horizontally and tied it down with a bracket. Pressure gauge has stayed at 60 psi so far, whereas it used to go up 110 psi overnight.

 
5.0

Product works well - perfect

By JD

from Florida

Verified Buyer

Comments about THERM-X-TROL ST-12 Expansion Tank:

WOrks perfect

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Q&A: Ask the Questions, share answers

Do you have questions about this product?

get answers from real customers and in-house experts with AnswerBox.

6 Questions | 18 Answers
Displaying questions 1-6
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    Is it OK to mount expansion tank horizontally ?
    Thank.
    Asked on 2/21/2014 by Val from Monroe, NJ

    4 answers

    • CUSTOMER CARE

      A:

      NO, the manufacturer requires the tank be mounted vertically only.

      Answered on 3/14/2014 by PexSupplyStaff from New York
    • VERIFIED BUYER

      A:

      Yes, just make sure that it is properly supported

      Answered on 2/21/2014 by gregknowswater.com from Oregon
    • VERIFIED BUYER

      A:

      Yes, I would think so.
      Mine is pitched downward at about a 45 degree angle. At horizontal the water as it expands will still have a place to go to.
      I would be sure to provide some king of support for the tank - strap or wood support or hanger - of some sort. As the tank partially fills with water it will be heavy and may tear itself away at the connection point.
      Four - Five years ago the internal bladder on mine failed and the whole tank filled with water. If I had not strapped it to the floor rafter above it probably would have broken away from the water feed line and flooded the basement.
      Good luck

      Answered on 2/21/2014 by Anonymous
    • VERIFIED BUYER

      A:

      Yes most applications have the tank set up horizontally.

      Answered on 2/21/2014 by Anonymous
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    WHAT DOES THE AIR IN THE TANK DO
    Asked on 1/8/2014 by BILLY from OHIO

    4 answers

    • VERIFIED BUYER

      A:

      The air equalizes the pressure. There is a rubber bladder in there. The
      air provides a cushion that allows the water to expand. The pressure of the
      air should be equal to the pressure of the water. If there is no air in
      there, the tank just fills with water. You need the expansion tank because,
      if you are heating a lot of water, the hot water (and steam) will blow off
      your pressure relief valve without someplace to go.

      Answered on 1/10/2014 by Anonymous
    • VERIFIED BUYER

      A:

      The air tank contains an diaphragm that expands & contracts when the hot
      water is used. As water is heated it expands and this manages a more
      consistent pressure in the line otherwise the fixtures bear pressure
      fluctuations which cause accelerated wear, leaks, drips etc. hope that
      helps.

      Answered on 1/8/2014 by Anonymous
    • VERIFIED BUYER

      A:

      Water in your plumbing system expands when the temperature increases.  When the water in your hot water tank is heated to the recommended ~120 to 140 degrees F, that expansion can become significant and the resulting jump in pressure could damage your plumbing.  The expansion tank is designed to accommodate the extra volume of water that results from thermal expansion.  When the pressure drops from cooling, the air in the expansion tank pushes the extra water back into your water heater/plumbing.  It is basically a pressurized overflow reservoir with a bladder separating the water and air.

      Answered on 1/8/2014 by Anonymous
    • VERIFIED BUYER

      A:

      There is a bladder between the water side and the air side.  Let's assume that you have all the faucets closed.  When the water pump runs it pushes water into the water side of the tank.  As the volume of water increases in the tank it reduces the volume available to the air and thereby compresses the air.  (Remember fluids essentially don't compress whereas gasses compress readily).  The water pressure and the air pressure in the tank are the same pressure.  When the water pump reaches its preset shutoff point, the tank has a large volume of water inside and a small volume of (compressed) air .  Now, when you open a faucet the water flows from the tank without the water pump running.  As the volume of water in the tank is reduced the air in the tank takes up a larger volume than it previously used and the pressure (air and water) is reduced slightly.  As more and more  water is expelled the pressure will eventually drop to the water pump's start-up pressure and the whole cycle repeats itself.  Cumulatively this uses less electricity than a water pump running at high pressure each time you need a couple ounces of water.
       
       

      Answered on 1/8/2014 by Anonymous
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    I have a 75 gallon gas water heater. I used a watts water gauge to see that my usual water pressure is 60psi. I have a pressure reducing valve where water enters my house.

    Overnight, the red high-water mark shows 120psi when I check it in the morning. As soon as I open a HOT water faucet, the pressure drops to 60psi. On the next morning, I see the 120psi on the red high-water mark and open a COLD faucet and pressure drops from 120psi to 60psi. So opening HOT or COLD both relieve the pressure.

    So, I purchased an ST-12 and installed it on the cold water side of my water heater. I used a bicycle pump to pre-set the ST-12 to 58psi. Now when I wake up in the morning, the red high-water-mark shows 95psi(instead of 120psi). But 95psi is still seems too high! When I tap on the ST-12, it is hollow on the lower part of the tank.

    What max pressure should I expect after installing an ST-12?

    Do you think my pressure regulator valve is broken? Or is there something else that I'm missing?
    Asked on 8/14/2013 by PeterL from San Mateo, CA

    2 answers

    • VERIFIED BUYER

      A:

      It makes sense that opening either hot or cold drops the pressure to the proper set point, which is, in your case 60 psi as determined by your incoming regulator. Both the hot and cold systems are effectively tied together at the tank so what your seeing is correct. What is not correct is your morning pressure. The pressure can be increased by only 2 ways, starting with a volume of water and then heating it or trying to force more water into the same volume. Do you know what your incoming pressure is? I suspect that it's 120 psi and that your pressure reg is not doing its job, allowing the outlet side to climb to match the inlet side over time and then when you open the outlet side, it quickly gets back to the proper set point. If your incoming pressure is less than 120, then you are getting a pressure increase by the heating and expansion as mentioned earlier. The X tank is taking up some of the pressure, as indicated by your 95 psi reading, my guess is that if you waited long enough, the system would get up to 120, even with the X tank. Remember that since water is not compressible, it takes very little leak by at the regulator to increase the pressure. Don't be fooled by tapping on the tank, they always appear to be empty when you do this, but they're not. Let me know how you make out.
      Jeff F.

      Answered on 8/15/2013 by Anonymous
    • VERIFIED BUYER

      A:

      The tank needs to be on the hot water side. When the water is heated, it
      produces pressure. As for the preset pressure in the ST-12, if you set the
      pressure @ 58 psi, the tank will not start to adsorb the excess pressure
      from the water tank until the pressure reaches the preset pressure. Review
      the preset pressure setting as per instructions.

      Answered on 8/15/2013 by Anonymous
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    Is this a potable tank?
    Asked on 7/24/2013 by Rachale

    4 answers

    • VERIFIED BUYER

      A:

      No it is a pressure expansion tank for a hot water heating system.
      Joe
      <*))}}}}>><{{
      Referrals Welcomed - no business too big or small

      Answered on 7/24/2013 by Anonymous
    • VERIFIED BUYER

      A:

      Yes, it is! My wife is using it in some of her cooking prep; I sometimes drink from it, too!

      Answered on 7/30/2013 by Anonymous
    • CUSTOMER CARE

      A:

      Yes, this tank is designed for potable water plumbing applications.

      Answered on 8/5/2013 by PexSupply Staff from NY
    • VERIFIED BUYER

      A:

      I believe that this is a bladder style expansion tank that is typically used for a boiler system. It could be used for potable water but I doubt that the pressure rating on it would make it very useful for water systems. These tanks usually only operate around 12 psi which is quite a ways from the ~ 60 psi which is what you would want for a potable water source. You would need to check the pressure specification for it. Also, this tank is very small which would mean that the supply pump would be cycling on an off quite often. The larger the better for a well system.

      Answered on 8/6/2013 by Anonymous
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    The description states that the THERM-X-TROL ST-12 Expansion Tank should be used in an "open loop" setting. Why not a closed loop setting if the temperature it's used for is never higher than 140°, and the pressure is less than 60 psi?
    Asked on 4/11/2011 by norbrook from West Caldwell, NJ

    3 answers

    • CUSTOMER CARE

      A:

      According to the manufacturer, the ST series tank could be used in the described closed-loop system.

      Answered on 4/12/2011 by PexSupply Staff from NY
    • VERIFIED BUYER

      A:

      You really should be OK if you bleed some air off.
      It is pre-charged to 60psi, which means you wouldn't get any benefit from this. After all, the main purpose of these is to prevent the actuation of the pressure relief valve.

      Answered on 4/3/2012 by Kevin from Denver, CO
    • A:

      internal plastic liner for corrosion resistance in system with high oxygen. This would work fine in a closed system. . . but you don't need the extra protection for an O2 free system. There are cheaper ones for that. This is for potable water.

      Answered on 10/15/2012 by bud from KS
  • THERM-X-TROL ST-12 Expansion Tank

    Q:

    I have a 50 gallon,60 psi water heater which requires a ST-5 expansion tank.Is it ok to use an ST-12 instead?
    Asked on 12/16/2010 by Prwtomastoras26

    1 answer

    • CUSTOMER CARE

      A:

      Yes, you can use an ST-12 tank. You can always go bigger with expansion tanks, just never smaller.

      Answered on 12/17/2010 by PexSupply Staff from NY
Displaying questions 1-6

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