Watts EX-30 Hydronic Expansion Tank 4.5 Gallons

Original price was: $89.97.Current price is: $67.70.

28 in stock

SKU: 1133528 Category:


The Watts ETX-30 is a non-potable water expansion tank designed for use in closed loop hydronic heating systems. It helps to maintain system pressure by absorbing the expansion of heated water, preventing the relief valve from opening and releasing water or air. Here’s a breakdown of its key features:


  • Capacity: 4.5 gallons (17.08 liters)
  • Connection size: 1/2-inch MNPT (male National Pipe Thread)
  • Pre-charged pressure: 12 psi (pounds per square inch)
  • Construction: Carbon steel with epoxy finish for durability and corrosion resistance
  • Diaphragm: Flexible butyl diaphragm separates water from the air chamber
  • Compact size: Saves space and is easy to install
  • Temperature rating: 240°F (115°C)
  • Standards: Meets ASME TPI and NSF 61 standards for safety and quality


  • Prevents pressure relief valve activation: The tank absorbs expansion, preventing the relief valve from opening and releasing water or air, saving water and maintaining system pressure.
  • Reduces system stress: By absorbing expansion, the tank reduces stress on pipes and other components, extending their lifespan.
  • Improves system efficiency: Maintaining proper pressure helps the system operate more efficiently.
  • Compact and easy to install: The small size makes it suitable for various installations, and the pre-charged pressure simplifies setup.
  • Durable construction: The carbon steel and butyl diaphragm ensure long-lasting performance.


  • Residential and commercial closed loop hydronic heating systems
  • Boilers
  • Hot water heaters
  • Solar thermal systems

Overall, the Watts ETX-30 is a reliable and effective expansion tank for hydronic heating systems. It’s a popular choice for its affordability, durability, and ease of use.

Here are some additional things to consider when choosing an expansion tank:

  • System size: Choose a tank with enough capacity to handle the expansion of water in your system.
  • Connection size: Make sure the tank’s connection size matches your system’s piping.
  • Pre-charged pressure: The pre-charged pressure should match your system’s operating pressure.
  • Temperature rating: Choose a tank with a temperature rating that exceeds your system’s maximum operating temperature.

Additional information

Weight 9.37 lbs


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