Don’t get caught in the heat: the truth about expansion tank placement

When it comes to plumbing systems, expansion tanks play a crucial role in maintaining pressure and preventing damage. However, a common question that arises is whether the expansion tank should be connected to the hot or cold water line. This blog post delves into the intricacies of expansion tank placement and provides a comprehensive guide to help you make an informed decision.

Expansion Tanks: A Vital Component

Expansion tanks are essential components in plumbing systems that prevent excessive pressure buildup caused by thermal expansion. As water heats up, it expands in volume. If this expansion is not accommodated, it can lead to pipe bursts, leaks, and even damage to appliances.

Hot or Cold: The Dilemma

The placement of an expansion tank depends on the type of system it is installed in. There are two main types of expansion tanks:

Closed Expansion Tanks

Closed expansion tanks are typically used in closed-loop heating systems. These systems do not have a direct connection to the potable water supply. In such systems, the expansion tank should be connected to the hot water line.

Open Expansion Tanks

Open expansion tanks are used in open-loop systems, which have a direct connection to the potable water supply. In these systems, the expansion tank should be connected to the cold water line.

Reasons for Hot Water Connection

• Reduced Corrosion: Hot water lines have a higher temperature, which inhibits the growth of bacteria and corrosion. Connecting the expansion tank to the hot water line helps prevent corrosion and extends the lifespan of the tank.
• Thermal Expansion: As water heats up, it expands more significantly. Connecting the expansion tank to the hot water line allows it to accommodate the greater expansion.

Reasons for Cold Water Connection

• Potable Water Supply: Open-loop systems have a direct connection to the potable water supply. Connecting the expansion tank to the cold water line ensures that any overflow or backflow from the tank does not contaminate the potable water.
• Reduced Pressure Fluctuations: Cold water lines typically experience less pressure fluctuations than hot water lines. Connecting the expansion tank to the cold water line helps stabilize pressure and reduce the risk of water hammer.

Other Considerations

In addition to the type of system, there are other factors to consider when determining the placement of an expansion tank:

• System Pressure: The expansion tank should be sized based on the system pressure. A tank that is too small will not be able to accommodate the expansion, while a tank that is too large can cause excessive pressure fluctuations.
• Tank Location: The expansion tank should be located in an easily accessible area and protected from freezing temperatures.
• Maintenance: Regular maintenance, such as checking the air pressure and draining the tank, is essential to ensure the proper functioning of the expansion tank.

Recommendations: A Balancing Act

Determining whether an expansion tank goes on hot or cold depends on the specific plumbing system and its operating conditions. Closed expansion tanks should be connected to the hot water line, while open expansion tanks should be connected to the cold water line. By carefully considering the factors discussed above, you can ensure the optimal placement of your expansion tank for a safe and efficient plumbing system.

Frequently Asked Questions

Q: Why is it important to connect the expansion tank to the correct water line?
A: Connecting the expansion tank to the wrong water line can result in reduced efficiency, corrosion, and potential contamination of the potable water supply.

Q: What happens if the expansion tank is not sized correctly?
A: An undersized tank will not accommodate the expansion, while an oversized tank can cause excessive pressure fluctuations.

Q: How often should the expansion tank be checked and maintained?
A: Regular maintenance, including checking the air pressure and draining the tank, is recommended every 6-12 months.