Therm-X-Trol ST-5 Thermal Expansion Tank (2.0 Gal Volume)


Brand: Amtrol

Mfr Part#: 140N43

Model: ST-5

UPC#: 642031395665

Availability: In Stock
Usually ships: Today, if ordered by 3pm
Qty Price
$39.95 / each
x4 $151.80 / box & Free Shipping
(4 x $37.95 / each)
  • Description
  • Literature
  • Reviews (1)
  • FAQs (2)

Amtrol ST-5 (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-5 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;

Standards & Approvals:
NSF/ANSI 61®, IAPMO, SBCCI & City of Los Angeles listings.

Amtrol ST-5 Applications:
Residentail water heaters, laundromats, dormitories, office/apartment buildings, restaurants, etc.

Technical Specifications:

  • Factory pre-charged 40 psig;
  • System connection: 3/4" male threaded;
  • Stainless steel system connection;
  • Max. operating temperature: 200F;
  • Max. operating pressure: 150 psi;
  • Expansion tank volume: 2.0 gallons;
  • Max. acceptance factor: 0.45;
  • Height: 12-5/8";
  • Diameter: 8";
  • Shipping weight: 5 lbs.


5-year manufacturer's warranty.
Therm-X-Trol ST-5 Thermal Expansion Tank (2.0 Gal Volume) has an average 5.0 out of 5 rating based on 1 user review.
2 of 2 people found this review helpful.
Nice quality tank.
By Bob the builder (from Eastern Canada) on 11/25/2011
I've used these in many installs and they always do the trick. The stainless steel connections eliminate any risk for rust.
Was this review helpful?  Yes / No
Indicate an email address where you wish to receive the answer to your question.
Enter numbers shown above without spaces. This step helps us to prevent automatic submissions.
I purchased my home as new construction years ago and this model was installed. I recently purchased this unit again as a replacement but found the pressure in my house is 65psi. Is it okay to increase the pressure in the tank to match the home water pressure?
Read 1 answer
1 of 2 people found this answer helpful.
Yes, you can (and in fact have to) increase the pressure in the expansion tank to match the system pressure. You'll find the details in the installation manual.
Answered on 2/4/2013 by PexUniverse Customer Service
Was this answer helpful?  Yes / No
I am having a problem I am unable to check the pressure of the expansion tank. I replaced the valve stem and still nothing. The pop off valve is still tripping near the end of the heating cycle. When I put air into the unit my gauge on the compressor shows 40lbs. I am unable to check it with a tire gauge. Do I need a new expansion tank?
Read 1 answer
2 of 3 people found this answer helpful.
A common condition indicating that there's something wrong with the expansion tank is when the pressure relief valve goes off. If you're unable to check internal pressure, the optimal solution is to replace the tank. If you did not experience similar issues in the past, the same expansion tank model would be suitable. If you had similar issues when the tank was new, it may be best to get a larger model (1 size up).
Answered on 12/12/2012 by PexUniverse Customer Service
Was this answer helpful?  Yes / No
The following was added to your shopping cart: ×

Forgot Your Password?

Enter your e-mail address below.
You will receive an e-mail
with password reset instructions.


Estimate Delivery Date & Cost

Ship to Zip Code:
Qty (Optional):