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Honeywell TK300-30

4.4 Gallon Bladder-Type Expansion Tank


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Honeywell Expansion Tanks absorb hot water expansion in closed heating systems. They are equipped with butyl diaphragms to separate the air from the system water. Pre-pressurized, the tank keeps fluids circulating and maintains minimum pressure.
  • Butyl/EPDM diaphragm- 9 times better than natural rubber
  • Deep-drawn steel tank
  • Controls system pressure
  • Air-tight cushion-factory pre-charged to 12 psig and 100% tested


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
9 lbs
11 Inches
15 1/2 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.