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Water Heater Thermal Expansion Tanks

A thermal expansion tank is designed to help protect potable (drinkable) hot water systems, helping to maintain them and keep them working efficiently. They are used to absorb excess water pressure, which can be caused by thermal expansion as water is heated. With a properly installed tank, the system pressure will be maintained, and will help prevent added stress to various components, saving you headaches - and money - down the road.

Water Heater Thermal Expansion Tanks
Protect your plumbing in the event of a pressure increase with these quality thermal expansion tanks
thermal expansion tanks These expansion tanks feature:
  • Safely controls thermal expansion by accepting the expanded water and keeping the system pressure safely under the relief valve setting
  • Saves water & energy: unlike a pressure relief valve that wastes heated water when activated, these tanks allow the expanded water to be stored in the tank for future use
  • Durable stainless steel (Type 304) connections
  • Food grade reservoir means the tank works great with potable (drinking) water
  • Reduces wear and tear on safety valves, valve stems, and ball seals
  • Maximum operating temperature: 200°F
  • Maximum working pressure: 150 PSI
  • Factory pre-charge: 45 PSI
  • Butyl rubber diaphragm, food grade polypropylene liner
  • Complies with low lead laws - less than .25% weighted average lead content for wettable surface areas
  • Can be installed in any orientation, vertical, horizontal or diagonal
  • Click here for detailed specifications
  • Click here to view a typical installation diagram
Sizing Chart
Description Max Gallon
Price & Quantity
#A101 water heater thermal expansion tank - 3/4" connections 2.1 $39.93
#A102 water heater thermal expansion tank - 3/4" connections 4.75 $49.88
#A103 water heater thermal expansion tank - 1" connections 14 $114.39
#A104 water heater thermal expansion tank - 1" connections 20 $162.87

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Frequently Asked Questions

Q. "What is thermal expansion?"
A. When water is heated, it expands in volume by 2 - 3%, depending upon the initial and final temperature. This can mean as much as three or four extra gallons of water in a closed system. If there is no demand for hot water, the expanded volume of water has no place to go. Since water is not compressible, the expanded water cannot be accommodated in the piping system, and therefore it creates hydraulic pressure, exerting a potentially hazardous stress on the system.

Q. "What is a closed system?"
A. It is a system that uses a pressure reducing valve when water service pressure is too high for residential applications, usually above 80PSI.

Q. "What size expansion tank should I order for my water heater?"
A. This depends on the size of your water heater and your water pressure. For most small water heaters usually the A101 works. Please refer to this thermal expansion tank quick-sizing chart to find the appropriate thermal expansion tank for your system.

Q. "Your typical installation diagram shows mounting these expansion tanks in a vertical position. Can they be mounted horizontally?"
A. Yes. According to the manufacturer, the A101, A102, A103 and the A104 expansion tanks can be installed horizontal, vertical or even diagonal. Inlet threads up, down or sideways, it doesn't matter. These thermal expansion tanks can be mounted in any orientation and the tank will function correctly.

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