Heres how expansion tanks work and how to install one in your system. It’s especially important in closed plumbing systems where water cant flow back into the main supply. A water heater expansion tank—or thermal expansion tank—is a small tank added to a water supply pipe. · learn what a water heater expansion tank is, why you need it, how it works, and how to choose and install it. Keep reading to learn why this small add-on could save you big trouble. Water heater expansion tank - 10. 3 gallon, 3/4 national pipe thread fuel (nptf) $267. 26 in stock quantity add to cart Neo-pure 0. 52 gal thermal expansion tank - 3/4 mnpt – maintains safe pressure for water heaters with backflow preventers, butyl diaphragm & corrosion-resistant finish (white) · this post covers what a thermal expansion tank is, why it matters, and how it actually works. · a water heater expansion tank absorbs pressure from heated water, preventing plumbing damage. · what is a water heater expansion tank? Find out the types, sizes, codes, and faqs of expansion tanks for your water heating system. · without an expansion tank , your water heater and plumbing can take the hit. It acts as a safety device and minimizes the risk of pressure damage, bursts, and leaks in a homes plumbing system.