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Amtrol

AMTROL ST-5 Thermal Expansion Tank

  • Based on 489 reviews
Condition: New
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$72.00 Why this price?
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Availability: In Stock.
Fulfilled by NYDIRECT
Arrives Monday, May 18
Order within 22 hours and 59 minutes
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Features

  • Metal
  • Made in USA
  • Accepts expanded water caused by thermal expansion
  • Returns water to the system when hot water is used
  • Prevents the relief valve from going off
  • Inline thermal expansion tank
  • Accepts expanded water caused by thermal expansion
  • Returns water to the system when hot water is used
  • Prevents dripping faucets, intermittent toilet fill and pressure relief valve discharge
  • Protects water heater, appliances and fixtures

Description

AMTROL ST-5 Thermal Expansion Tank From the Manufacturer Amtrol invented the thermal expansion tank to control pressure build-up in closed, hot water systems. This prevents the water heater pressure relief valve from opening, saves energy and eliminates a potential safety hazard. All Therm-X-Trol expansion tank

Manufacturer: ‎AMTROL


Part Number: ‎ST-5


Item Weight: ‎3.08 pounds


Product Dimensions: ‎8 x 8 x 13 inches


Item model number: ‎ST-5


Is Discontinued By Manufacturer: ‎No


Size: ‎one-size


Color: ‎White


Material: ‎Molded Polypropylene


Power Source: ‎Ac/dc


Item Package Quantity: ‎1


Included Components: ‎Expansion tank


Batteries Included?: ‎No


Batteries Required?: ‎No


Date First Available: January 16, 2007


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Monday, May 18

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

  • Klarna Financing
  • Affirm Pay in 4
  • Affirm Financing
  • Afterpay Financing
  • PayTomorrow Financing
  • Financing through Apple Pay
Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Similar Products

Top Amazon Reviews

    • Perfect and easy drop-in replacement.
My old failed tank was the same model - this new one was dead easy to swap in. Following the instructions I lowered the pressure a little to match line pressure, put tape on the threads, pushed in the plastic "turbulator" thing, and screwed it on. Very easy repair saving a lot compared to calling a plumber - and I hate plumbing and usually pay someone else to do it. ... show more
Reviewed in the United States on February 20, 2025 by Stephen P. Hill
    • quite useful product
functional and saves us money
Reviewed in the United States on January 3, 2026 by CELESTE G.
    • Very Solid Expansion Tank
Installed very easily. Check you home system water pressure first, then pre charge this tank with that pressure with a standard tire pump. Install with Teflon tape, screw it on with light pressure. Good to go for another 7 years! Nice. Plumber wanted almost $300 for a full install. If you are only slightly handy, you can do this. ... show more
Reviewed in the United States on April 26, 2026 by Starlifter777
    • Old one out, new one in.
Amtrol is a great standard product and the indicator on the bottom is a good feature.
Reviewed in the United States on December 15, 2025 by MikeR
    • Works like a tank
Just make sure the pressure in the tank matches your incoming water pressure and it works fine. However I’ve never had one last more than 4 or 5 years.
Reviewed in the United States on October 2, 2025 by Samohtdnal
    • Good investment
This is the second one i purchased. First lasted 5 years. I have a 40 PSI pressure swing and this takes care of the expansion. No leaks and I use it with the pre-charge pressure.
Reviewed in the United States on February 2, 2026 by Andrew
    • Update Dec24 - Do not trust this brand.
Review Image by anikko
Review Image by anikko
Review Image by anikko
Review Image by anikko
Review Image by anikko
Review Image by anikko
Review Image by anikko
Review Image by anikko
This unit is a direct replacement from the one I had on my water heater. It was a perfect fit, unscrew the original and put on the provided Teflon tape and screw it on. Simple and easy. Update Sep/2024 - Tank failed in about a year. Seller did not respond to warranty inquiry. Not sure if they are even the real deal. The second tank blew after 6 months and give run around on warranty. Don't trust this brand, useless warranty! Don't believe just try claiming the warranty and you will get the run around. These tanks are garbage. The leak senor does not work. My tank diaphragm rupture for months and the indicator shows nothing. All gimmick. In addition, the tank is not stainless steel it will rust like crazy. Check out the photos. The third tank blew even before I installed it. Pressure the tank to 80 PSI source PSI and it just pop! Was rated for 150 right? ... show more
Reviewed in the United States on February 21, 2023 by anikko
    • Expansion tank needed ASAP
Order was delivered earlier than expected … it works and functions as advertised. Thank You for your help to get it sent to me. It
Reviewed in the United States on December 25, 2025 by Nomad Welder

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