Expansion Tanks

Expansion Tank Size Calculator - This tool will help you find what size expansion tank you need and will suggest which model will work for your system.

Extrol tanks manufactured by Amtrol are ideal for hydronic heating systems. The Watts ET series expansion tanks are designed for closed radiant heat and hydronic heating systems. These tanks are not designed for potable water open systems. For these systems, go to Therm-X-Trol tanks under plumbing supplies.

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More About Expansion Tanks

An expansion tank is designed to relieve pressure in both a potable water and closed heating system. An expansion tank ensures a constant pressure is maintained within the pipes so they do not get damaged from excess pressure.

An expansion tank has two parts which are divided by a rubber diaphragm. The top portion of the tank is connected to the hot water system and is filled with water. The bottom portion is filled with air set at approximately 12 psi. As the hot water system is turned on or off, pressure increases. As pressure increases, the diaphragm in the expansion tank is pushed down. This compresses the air in the tank, creating more space for excess water to enter. This relieves excess pressure in the system and prevents pipes in the system from being damaged.

In the event that the diaphragm fails, the tank will completely fill with water. If this occurs, the tank must be replaced immediately. To check if the expansion tank is working properly, simply place your hand on the tank and feel its temperature. The top portion of the tank should feel warm to the touch, and the bottom portion of the tank should be room temperature. If the entire tank is warm, it is likely that the tank has completely filled with hot water.

Expansion tanks have capacities ranging from 2 gallons to several hundred gallons. To determine the size needed for your system, use the Expansion Tank Sizing Calculator.

At PexSupply.com, we offer a wide selection of Amtrol, Watts, Cash Acme, and Bell & Gossett expansion tanks to suit all of your plumbing and heating needs.

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