A Connecticut homeowner with a 30-year-old oil boiler had lukewarm showers, and a fix seemed to fall outside the HVAC company's license.

An aging oil boiler can be a sunk cost, especially after 30 years. Homeowners who switch hot-water production to a heat pump water heater can cut fuel use and lower energy bills while avoiding some of the headaches of older boiler-based setups.

Here's what to know

In the homeowner's Reddit post, they explained that the oil boiler serves as the house's main hot-water source. They also said Connecticut licensing rules contributed to the problem because work on the home's potable-water side would need to be handled by a plumber.

After 12 years in the home, the owner said the hot water has never been especially strong, and showers have become more disappointing. They described the water as "sometimes adequate and many times luke warm" and said it seemed like the burner "doesn't know there isn't enough hot water and then during the shower the oil burner turns on."

Commenters began to diagnose the issue.

One reply focused on the mixing valve first, advising, "Turn the hot water on and touch the pipe feeding into the hot side of the valve it should be very hot." The homeowner said the check passed: "The hot side of the mixing valve is very hot."

Commenters also tried to narrow down whether the issue was tied to one fixture. Asked directly, the homeowner answered, "Both showers." That rules out a bad shower component.

More background

The boiler is about 30 years old, although the homeowner noted that a new combustion chamber was installed in 2014. They also said the mixing valve tied to the oil burner was replaced in 2018, meaning significant parts have already been changed without fully fixing the weak shower performance.

One commenter said the tankless-coil design itself may limit what the system can deliver. As they put it, "Your coil is a spiral of copper with domestic water running through it," and "You'll never have a 'lot' of HW. Should be enough for a decent shower."

That same commenter took the very hot pipe at the mixing valve as a clue that "it's an upstream issue," and added that "it's a plumber issue not HVAC." Since the service company owner had already said he could not work on the potable-water side, any fixes still point back to a plumber.

Not everyone in the thread thought replacing the coil made financial sense. One commenter said, "You can pay someone to swap the coil but at 30 years old you're wasting your time." With both showers going lukewarm, the homeowner is left weighing repair costs against the equipment's age.

What can be done?

The replies sketched out a range of next steps based on the homeowner's budget. One commenter wrote, "Depending on what you want to spend, low end tankless replacement, middle (5-7k) add an indirect to the existing boiler, high end replace with system 2000 and indirext." If the underlying problem is on the potable-water side, a licensed plumber in Connecticut would still likely need to inspect the coil and related parts.

For homeowners who decide not to keep hot-water production on an aging oil boiler, Cala makes customizable smart heat pump water heaters that can help homeowners decrease their energy bills by heating water exactly when it is needed. 

A smart heat pump water heater also gives homeowners another option besides investing more in a 30-year-old boiler. In this homeowner's situation, the next step may be to compare a coil repair, an indirect tank, and a separate smart water-heating solution.

Where can I learn more?

These articles dig into the same repair-or-replace questions that come up with lukewarm showers and aging water heaters. 

• One homeowner chasing endless hot water found showers go weak when toilets flushed.

• Plumbers mocked an outdated water heater after a homeowner shared a sputtering unit.

• A homeowner pressed for answers after a plumber questioned heat pump water heaters.

• Cala says 50% more hot water can help end lukewarm showers.

• Another homeowner weighed incentives after an aging heater lost steam and bills loomed.

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