Originally Posted By: rmoore
This post was automatically imported from our archived forum.
It?s more properly referred to as a thermal expansion tank. On a closed supply system, such as occurs when you have a backflow preventer (check valve) or pressure regulator at the supply entrance, the heated water tries to expand and has no where to go. So?instead it increases pressure. Depending on initial pressure, and the amount of heat added, this can often lead to pressures over 150, which will cause the TPR valve to leak or possibly damage the plumbing.
The flexible bladder in the TX-tank allows this thermal expansion somewhere to go with only a small increase in pressure. If the system is ?open? to the main supply, then probably not needed (may be ?required?), but they do also help with water hammer and some install them just for that.
Usually installed on the cold water side, although I can?t think of a reason they wouldn?t work on the hot side other than the rubber bladder may deteriorate faster.
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