Boiler Expansion Tank Replacement in Northern Liberties

An older three-story home in Northern Liberties needed a focused boiler repair ahead of a larger renovation planned for the coming years. The boiler had been installed in 2007, but the installation had retained an older ceiling-mounted expansion tank. When we tested the system, its pressure began climbing quickly as the water heated.

A recently replaced relief valve was a clue

We had noticed that the boiler’s pressure relief valve had already been replaced. That did not tell us the cause by itself, but it gave us a reason to pay close attention to system pressure. After filling the heating system and starting the boiler, we watched the pressure rise rapidly.


The old expansion tank was waterlogged. It no longer had the air cushion needed to accommodate the expanding water as the system heated. Replacing a relief valve alone would not resolve that underlying problem.

Choosing a repair that fit the home’s plans

The ceiling-mounted tank had no isolation valve or dedicated service drain. Servicing it would ordinarily have meant draining more of the heating system. In an older three-story house, we wanted to avoid the additional work and potential complications of a full drain-down where possible.


The homeowner was planning a full rehabilitation in the coming years. Our goal was to address the pressure problem now without spending their money on work that did not need to be part of this repair.

Replacing the tank without a full system drain-down

We used a Rothenberger aerosol pipe-freezing kit to create a temporary ice plug in the line serving the expansion tank. That allowed us to isolate the tank connection without draining the entire heating system. 


We drained and removed the old tank, then installed a new bladder-type expansion tank.


We also added an isolation valve for future service and an automatic air vent to remove air from the line to the expansion tank. The result was a replacement installation with improved service access.

Testing through a complete heating cycle

The repair was not finished when the new tank was connected. We restarted the boiler and stayed through the heating cycle to watch how the system responded. Pressure remained stable throughout the cycle, including when the boiler water reached 170°F.



Testing at operating temperature confirmed that the rapid pressure rise had been resolved.

A practical repair for an older Philadelphia home

This Northern Liberties project called for an approach that accounted for both the existing heating system and the homeowner’s future plans. By isolating the tank connection with pipe freezing, we replaced the waterlogged tank without a full system drain-down and verified the repair under operating conditions.


If your boiler pressure climbs as the system heats, contact Rare Heating and Air to arrange an assessment. We will explain what we find and recommend a repair suited to your home.
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