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Amtrol FILL-TROL 110

4.4 Gallon Bladder-Type Expansion Tank with Fill-Trol® Automatic Pressure Reducing Valve


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An expansion tank is a required component for all hot water boiler systems, and is designed to control system pressure and help reduce energy consumption of heating and circulating operations. These Amtrol expansion tanks are factory pre-charged and 100% tested to keep the diaphragm flush against the tank when the system is first filled with cold water. As the system water temperature increases, the expanded water is absorbed by the tank. As the system water temperature reaches its maximum, the diaphragm flexes against the air cushion to allow for the increased water expansion. These expansion tanks feature a Butyl/EPDM diaphragm for superior air retention, nine times better than natural rubber. 

The AMTROL FILL-TROL® system consists of a specially adapted EXTROL pre-pressurized, diaphragm-type expansion tank, and the FILL-TROL, a specially designed, automatic, pressure-reducing fill valve.

Standard Features

  • Pre-pressurized, diaphragm-type expansion tank with a standard charge of 12 PSI
  • Tanks are of welded-steel construction Extrol® Tanks
  • Hydronic heating systems and can be used in glycol systems
  • Recommend installing Extrol® into bottom of purger using a single 1/2" nipple for both pipe connection and mounting
  • Can be used in hot water heaters, hydronic heating systems and in glycol systems
  • Includes Fill-Trol®, automatic pressure reducing valve
  • Fully adjustable up to 100 PSIG maximum working pressure Therm-X-Trol® Tanks
  • Designed to accept increased water volume created when storage tank is heated, keeping system pressure below relief valve setting
  • System connection 3/4" brass
  • Listed by IAPMO, SBCCI and NSF61

Expansion Tank Type

There are two basic expansion tank types: Plain steel and bladder-type. Both are intended to control the high end pressure of your boiler system and keep the relief valve from opening due to increased system pressure caused by the expansion of water. Plain steel tanks have no moving parts, and require a separate pressure reducing valve to maintain initial fill pressure of 12 psi (or higher depending upon the requirements of your system). This type of tank looses its air cushion over the years and will need to be drained periodically. Bladder-type tanks contain a moving bladder, and requires either a separate pressure reducing valve (as mentioned above) or a fill-trol valve to maintain initial fill pressure of 12 psi (or higher depending upon the requirements of your system). This tank will not lose its air cushion unless the bladder becomes detached, at which point the tank would need to be replaced.

Expansion Tank Type
Max Temp
240 °F
Tank Volume
4.4 Gallons
Max Accept Volume
2.5 gallons
Max Water Pressure
100 PSI
Product Weight
10 lbs
11 Inches
17 3/8 Inches

In 2002 Alpine Home Air Products became the first company to sell heating, air conditioning and indoor air-quality products online. We have proudly served hundreds of thousands of customers, helping them save time and money by buying their products direct.