Expansion Tanks for Heating

We stock a wide range of expansion tanks for residential and commercial hydronic heating applications, including baseboard/radiator, radiant floor heating and others.
Amtrol heating expansion tank series include:
Extrol - the most popular expansion tank in the USA, used for closed loop hydronic and radiant heating applications;
Fill-Trol - comprised of an Extrol series tank with a fill valve;
Radiant Extrol - for open-loop heating systems or systems with high level of dissolved oxygen in water;
Calefactio HGT expansion tanks are cost-effective alternative to Amtrol Extrol, Watts ETX and B&G HFT.

About Expansion Tanks For Hydronic Heating

Expansion tank is a must-have component in a hydronic/radiant hot water heating system. It absorbs excess hot water generated in the system as the former expands. When water cools down and decreases in volume, it is released back into the system. This process helps to maintain a safe pressure level, takes the stress of the piping and components and prevents frequent discharge of the pressure relief valve.

Difference between diaphragm and bladder type expansion tanks

Bladder and diaphragm expansion tanks operate in the same manner, but differ in construction.

Diaphragm expansion tanks such as ones made by Amtrol are constructed of a steel shell with built-in rubber diaphragm located about in the middle. The diaphragm separates the tank into (2) separate chambers - one with pressurized air, the other - with system water. As hot water expands and enters the tank, it presses against the diaphragm while pressurized air on the other side “cushions” the expansion, thus maintaining system pressure equilibrium and at the same time allowing for absorption of excess water.

Bladder type expansion tanks are comprised of a rubber “balloon” installed inside a pressurized steel shell. As hot water expands, it enters and expands the bladder, while pressurized air inside the tank chamber presses back against the bladder and acts as a cushion. As a result, system pressure is maintained within safe levels and excess water is absorbed.
Bladder type tanks are expected to have a longer lifespan than diaphragm ones since there’s no direct contact of water with steel shell and no corrosion. In practice however, corrosion is rarely an issue in closed-loop heating systems if a proper air eliminator device is installed.