Heating system sparks attention after expansion tank comes loose

"You can look at cpvc wrong and snap it when it's old and brittle."

An HVAC technician ran into an unusual failure report after a customer said an expansion tank had blown off the system and mentioned finding a spring.

The situation became clearer once the photos arrived, and the technician posted one on Reddit with the caption, "Never seen anything like this before."

Here's what to know

In a Reddit thread, the photo appeared to show a metal coil where the tank connection had failed. The original poster said the image came after a customer called to report that the expansion tank had blown off the system and had mentioned a spring.

For some users, the first concern was how the tank had been mounted.

One person said, "Most likely wasn't supported properly. Expansion tanks need independent support. You cannot hang them off of existing piping, no matter how small they are."

Other users focused less on the mounting and more on the twisted metal visible in the photo. One user said, "That spring is the threads from the female adaptor. Bad fitting from factory," and the OP replied that the same setup "uses this exact tank with no support" and leaves it "just hanging off the threads as this one was."

While system upgrades can help lower utility bills and reduce exposure to rising energy costs, the thread centered on a heating failure and the possible causes behind it.

More background

Although the OP said they had "never seen anything like this before," the discussion branched into several possible explanations, including inadequate support, a faulty fitting, hard water, and water hammer.

Some of the discussion also turned to the risks of older plastic piping under added weight. One user recalled repairing a similar tank that was "free hanging off CPVC," prompting another to warn, "You can look at cpvc wrong and snap it when it's old and brittle."

To explain what an expansion tank does, one user offered a simple example: heat a completely filled, sealed milk jug to 130 degrees Fahrenheit and watch the pressure rise as the water expands. The point was that the tank provides a place for that extra volume to go.

Warranty concerns came up as well. One user said the OP should contact the manufacturer directly, arguing that this was a "low pressure system (boiler expansion tank)" and that "there is no way that tank should have failed under max 30 PSIG."

What can be done?

If an expansion tank is hanging only "off the threads," the OP said homeowners may want a qualified pro to check whether the setup meets manufacturer requirements and whether the piping and fittings are carrying too much weight.

For people using an aging boiler or considering a broader equipment upgrade, Comfort Plan includes $0-down options that can lower heating and cooling costs by up to 50%. Palmetto says its Comfort Plans also include 12 years of free maintenance, which could help homeowners avoid surprises like the one discussed in the Reddit thread.

If a part looks suspect, document the damage and ask about warranty coverage. One user specifically said to contact the manufacturer directly because they are "generally really good with warranty," especially if the tank threads failed on a low-pressure boiler system.

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Where can I learn more?

For more on the kinds of problems raised in this thread, these stories examine similar issues involving support, fittings, and pressure. They follow homeowners and plumbers as they work through burst tanks, questionable installs, and leak sources.

• A homeowner learned an upside-down install is normal after a burst expansion tank raised alarms.

• In Florida, plumbers warned homeowners to please only use brass for expansion tank fittings.

• After a $500 quote, plumbers said the easy swap needs support to last.

• A plumber told a homeowner that reused push-fit fittings can leak around a new tank.