Skip to Main Content
Logo

Thermal Expansion

How It Works

When water is heated, its density decreases and volume expands. Because water is not compressible, the extra volume created by expansion needs somewhere to go. During no-flow periods in a system, pressure reducing valves, backflow preventers, and other one-way valves are closed, thus eliminating a path for expanded water to flow back to the system supply. That is when system pressure increases, causing a number of undesirable and potentially dangerous problems.

The Difference Between Water Containment & Water Relief Solutions

Water Containment solutions allow for thermal expansion while containing thermally expanded water in the plumbing system. Our full line of thermal expansion tanks are considered water containment devices, requiring no installation of discharge lines or drains.

Water Relief solutions discharge thermally expanded water at a pressure setting that is below the setting of the water heater's temperature and pressure relief valve. We offer variety of water relief solutions that can be installed on the system piping, in a water closet, or on an outside faucet. These products must be piped to a suitable drain or discharge location.

Diaphragm Expansion Tanks

When the water volume increases with nowhere to go, an expansion tank allows excess water to enter the pre-pressurized tank. As the temperature and pressure reaches its maximum, the diaphragm flexes against an air cushion to allow for increased water expansion, because unlike water, air is compressible. When the system is opened again or the water cools, water leaves the tank and returns to the system.

Control Thermal Expansion in Potable Water Heating Systems

Our potable water expansion tanks are designed to absorb the increased volume of water created by thermal expansion and maintain a balanced pressure throughout the potable water supply system. They are used to prevent plumbing system and/or water heater damage as well as unnecessary relief valve discharge caused by excessive pressure from thermal expansion.

Other Potable Water Thermal Expansion Solutions

We offer several alternatives for pressure relief. While unlike an expansion tank such products do not prevent against loss of water, they do limit high pressure and prevent issues associated with thermal expansion.

Products include:

  • The 530C calibrated pressure relief valve
  • The LFBRVM1 combination ball valve and relief valve
 

Control Thermal Expansion in Non-Potable Water Heating Systems

Our non-potable water expansion tanks are designed to absorb the increased volume of water caused by thermal expansion and maintain a balanced pressure throughout the a water heating system. They are used to prevent system damage and unnecessary relief valve discharge caused by excessive pressure from thermal expansion.

Plumbing Code Requirements

Both the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC) require thermal expansion control to be addressed in plumbing systems. A temperature and pressure (T&P) relief valve is not considered a thermal expansion device. This is because when water is allowed to continuously drip from the T&P relief valve, minerals from the water can build up on the valve, eventually blocking it. This blockage can render the T&P valve useless and potentially lead to hot water heater explosions.