In this video, Bill Bailey, a hydronic specialist with 35 years of experience, explains expansion tanks in hydronic systems. In a closed-loop hydronic system, water is filled into the system, and after eliminating air, the water is heated. As water heats up, it expands, necessitating a mechanism to accommodate this expansion. The primary goal is to avoid water coming out through the relief valve, as constantly replenishing the system with new water introduces air, creating a counterproductive cycle.
Expansion tanks have evolved over the years, from open steel expansion tanks to closed steel expansion tanks. Newer options, including diaphragm expansion tanks have improved upon older models to effectively separate air from water, allowing for expansion without the risk of air reintroduction.
Bladder tanks are an advanced version of the diaphragm tank. In these products, a bag or bladder holds the system water, and the outer compartment serves as the air cushion. They essentially follow the same principle as diaphragm tanks but are designed for larger systems.
Both bladder and diaphragm tanks need to be sized correctly for the volume of expansion in the system.
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Bill Bailey is a contributor with Slipstream.
