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Therm-X-Trol ST-5 Expansion Tank

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  • Maintains system pressure at safe levels
  • Eliminates BTU and water wastes
  • Can be installed in hospitals, office- and housing buildings
  • View More Details
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Product Details

About This Product

The Therm-X-Trol Expansion Tank can be used in a variety of places such as apartments, office buildings and hospitals. This expansion tank helps eliminate BTU and water waste. The tank helps protect the fixture and heater. This tank is easy to install.

Highlights

  • Helps eliminate BTU and water waste
  • Helps protect heater and fixtures
  • Limits the system's pressure buildup
  • Can be used in office buildings, apartments, hospitals and laundromats
  • Easy to install
  • 2 Gallon Tank Volume
  • Return Policy
  • California residents
     see Prop 65 WARNINGS

Product Information

Internet # 202268963

Model # ST-5

Specifications

Dimensions: H 13.25 in, W 8.25 in, D 8.25 in

Dimensions

Product Depth (in.)

8.25 in

Product Height (in.)

13.25 in

Product Width (in.)

8.25 in

Details

Pack Size

1

Product Weight (lb.)

4.25 lb

Returnable

90-Day

Warranty / Certifications

Manufacturer Warranty

5 YEAR

Questions & Answers

40Questions
caret
Q:I am replacing my hot water heater. My system uses a recirculating pump for better hot water distribution. Plumber has suggested an expansion tank. Can I use an expansion tank with a recirculation pump ?
by|May 5, 2024
1 Answer
Answer This Question

A:  Yes. Recirculation has no bearing on thermal expansion. I assume you are postulating that the thermal expansion tank could absorb the pressure drop created by the recirculation pump. That is not the case for several reasons. The most significant is that the thermal expansion tank is installed on the cold-water inlet side of the water heater. Therefore, it is not directly part of the hot water loop. As the cold water in the tank is heated and expands the diaphragm will move allowing the system to get larger so that pressure remains constant. In the old days the water would expand back into the street. But today it can’t due to the check valves in modern water meters. Remember to commission the tank properly by balancing the air pressure in the tank to your base line cold water pressure. Water pressures vary tremendously house to house. So, you must add or remove air in the tank to set it to your home’s water pressure during installation. Most people don’t so many tanks aren’t really doing anything.

by|May 6, 2024
    caret
    Q:My 2 expansion tanks were replaced by 1 fist size device. Now my remotely activated recirculating pump comes on when activated but the tankless heaters do not. Should I go back to 2 large expansion tanks?
    by|Mar 26, 2024
    1 Answer
    Answer This Question

    A:  Assuming the thermal expansion tank is installed in the correct location, on the cold-water input side of the water heater, I can see no relationship between the thermal expansion tank and a circulator not being able to create enough flow to actuate the flow switch in a tankless water heater. Further even if the thermal expansion tank was installed in the wrong location, I am having a hard time envisioning a situation where it absorbs the pressure differential created by the circulation pump preventing flow. I am not saying it’s impossible, but I have never seen or heard of it, and it is not where I would put my time investigating this issue. I would start with the tankless heater’s installation manual. Some heaters can be used with recirculation and for others it is not possible, and it will do damage to the heater. I would start by reviewing the manual for the heater and comparing the installation to the prodigal outlined by the manufacturer. Assuming the pump was sized and plumbed correctly I would confirm the pump is not air bound. When the system is drained for work to be done air is introduced into the piping system. It is common for air to get stuck in the pump’s volute. That air bubble will absorb the pumps energy and prevent flow. A circulator is not powerful enough to pass an air bubble, it must be manually purged. If you would like to discuss your situation further, you are welcome to give me a call. Chris 978 651 3301.

    by|Mar 26, 2024
      caret
      Q:what is the connection size? I'm looking for 1/2 inch
      by|Nov 6, 2023
      1 Answer
      Answer This Question

      A:  The connection size is ¾” male NPT (national pipe thread) I have never heard of a thermal expansion tank with a ½” connection. Are you sure that you are looking for a thermal expansion tank, which are used on water heaters? I ask because hydronic expansion tanks that are used on boilers typically have ½” connections. But those are different and the two are not interchangeable. Chris 978 651 3301

      by|May 9, 2024
        1 found this answer helpful
        caret
        Q:What is the difference between an ST-5 and an ST-5C?
        by|Sep 9, 2023
        1 Answer
        Answer This Question

        A:  The “C” at the end of the model number would indicate that the model is ASME “American Society of Mechanical Engineers” certified. This certification is required on certain projects and its requirements are extremely high and ridged. In my decades in the plumbing industry, I have never seen a situation where ASME rated product was required or used residentially. An ASME version of this product would be 20 to 30 times the cost of a non ASME version. In a sense it would be like going from regular auto parts to those used in aerospace applications.

        by|Sep 11, 2023
          Showing 1-4 of 40

          Customer Reviews

          4.8 out of 5

          • 4.8 out of 144 reviews
          • 97% recommend this product
          Filter by:
          Showing 1-10 of 144 reviews
          Tank OK but Schrader valve leaked pressure
          Before installing the ST-5 Amtrol Thermal Expansion Tank I needed to adjust the tank pressure to 60 psi to match my system pressure. When I removed the Schrader valve cover there was a hissing sound and the factory-set tank pressure leaked out. I checked that the valve was tightly seated and refilled to 60 psi. The pressure leaked back out due to a faulty Schrader valve from the factory. I could hear the hissing of the pressure escaping. I changed the defective valve with a new one from my parts drawer. The factory installed Schrader valve had a bent shaft and would not seat properly. I let the tank sit for an hour and rechecked the pressure. The replacement Schrader valve I installed is holding pressure, and is stable at 60 psi. I reinstalled the protective valve cover. The tank is marked "Made in USA", but the defective valve would have caused the tank to fail in service rendering the tank useless. This is an indication of poor quality control and the factory.
          by
            Tech Support was great. Simple and useful product.
            Installed this this week after my original expansion tank failed after 16years. The original was made by Amtrol so I went back to them and purchased this one. The installation guide wasn't super clear so I called Tech Support. To my pleasant surprise I was routed to a LIVE PERSON who answered my installation questions. That alone moved this review to five stars! The installation was straight forward after I watched several YouTube videos with guidance from Amtrol tech support. Make sure you match the air pressure inside the tank to the incoming water pressure. I used a pressure gauge to test and then used a bicycle pump to pump up the internal bladder to 60psi. Also, make sure you depressurize/turn off your water heater as part of installation. Tech Support mentioned that this tank needs to be installed with indicator pointed down for the indicator to work BUT you can install it upside down and it will work fine. If installed upside down then the indicator won't work. I will repipe my setup later to ensure I have it pointed down so I can use the little indicator and test the air pressure annually.
            by
              • Recommended
              1 found this review helpful
              Love the quality of it and that it is made in the U.S.A.
              Love the quality of it and that it is made in the U.S.A.
              by
              • Verified Purchase
              • Recommended
              Just installed this ST-5 tank
              First HOME DEPOT was excellent in shipping this. I ordered on 4/8 and got it on 4/9. However I had to wait a few days longer for the flex copper lines. Ive attached a picture and you might be wondering why I hooked it up this way. It was because there used to be a water softener there connected with flex copper lines too. So I unscrewed and used two new 12 inch brasscraft flexible copper lines and did a DIY support bracket. Everything worked GREAT! A few notes: 1) I did this because every time my 50 gallon water heater fires up, the pressure inside the tank would go from 45ish to 110ish or so. Not ideal. Right now it stays around 55ish. 2) Make sure you charge your tank to whatever your cold water pressure is and mine was about 50-52. 3) Every time I do plumbing something freaking leaks here and there; well NOT this time! I used a little silicone grease on the rubber gaskets and a little pipe dope for the connections where there is NO taper. For the tapered threads, I used 3-4 wraps of teflon tape and then pipe dope. Tighten good but I made sure NOT to overtighten. If there is a leak you can always tighten a little more. I was pleasantly surprised nothing leaked (and if you count there were SEVEN threaded connections! 4) Amtrol customer service is EXCELLENT! I was able to call and speak to a live tech support every time and they answered all my questions and "assured" me this connection is good. Technically you can put this anywhere on the cold side. It doesn't HAVE to be super near the WH. 5) You can see from my pic the pressure relief valve for the WH. It is NEW. My old one was 7 years old and stuck and I suspect that is why my water softener "exploded." Oh this and the fact that my house pressure reducing valve had a FUBARed o-ring which I replaced recently too. So for some time I was getting around 120-130 PSI in my plumbing. Everything is good and swell (no pun intended) now! -Charlie
              by
                • Recommended
                Well made product - clear instructions and easy to instal.
                Well made product - clear instructions and easy to instal.
                by
                • Verified Purchase
                • Recommended
                * Amtrol brand (USA made) * Easy to adjust and install * Seems to be quality made So far, work...
                * Amtrol brand (USA made) * Easy to adjust and install * Seems to be quality made So far, works perfectly. Hot water expansion is now under control and not affecting my cold water lines throughout the house. Important detail - make sure you match the pressure of this bottle to your cold water line pressure for best results.
                by
                • Verified Purchase
                • Recommended
                This appears to be a high quality product. It was easy to install and has reduced the rise in wat...
                This appears to be a high quality product. It was easy to install and has reduced the rise in water pressure due to thermal expansion to under 10 PSI. Really appreciated the free shipping to my local store.
                by
                • Pro
                • Verified Purchase
                • Recommended
                4 found this review helpful
                Disappointed
                This product arrived dented and scratched in an pristine and unmarred box. It obviously shipped this way from the factory or point of origin. Because my boiler was leaking due to excess pressure I had to install the expansion tank damaged as it was. Shipping this to a customer, in this condition. is totally unacceptable. Quality control must be non existent.
                by
                Response from chrisMay 16, 2016
                I am sorry for the inconvenience.Please note this product does not go on a boiler. This is a thermal expansion tank, which means its designed to go on a water heater; where the pressure is higher. Boilers operate at 15 PSI and thus use a tank called a hydronic expansion tank. If you have questions please feel free to call. Thanks Chris 978 651 3301
                • DIY
                • Verified Purchase
                2 found this review helpful
                Seems solid
                Bought an expansion tank in-store and read reviews on the product after the fact. Appeared to be a less quality product. Came across the Therm-X tank and the reviews were much better. So I ordered this online and had it shipped to my home. Product came as advertised and arrived early. I did try to just hand tighten tank because I didn't have a 12' crescent wrench. It leaked. Once I got the wrench and tightened it down it worked as expected.
                by
                • DIY
                • Verified Purchase
                • Recommended
                5 found this review helpful
                Easy to install, just match you house water pressure
                by
                • Verified Purchase
                Showing 1-10 of 144 reviews