"You can pay someone to replace the coil, but at 30 years old, it may not be worth it."

A Connecticut homeowner with a 30-year-old oil boiler had been dealing with lukewarm showers, and the likely fix appeared to fall outside the HVAC company’s license.

An older oil boiler can become an expensive problem over time. Some homeowners who switch hot-water production to a heat pump water heater can reduce fuel use and lower energy bills while avoiding some of the frustrations tied to older boiler-based systems.

What happened

In a Reddit post, the homeowner said the oil boiler is the home’s main source of hot water. They also said Connecticut licensing rules were part of the issue because work on the home’s potable-water side would need to be done by a plumber.

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

Commenters quickly started troubleshooting the problem.

One response pointed first to the mixing valve, saying, “Turn the hot water on and touch the pipe feeding into the hot side of the valve it should be very hot.” The homeowner replied that this check seemed to confirm the valve was not the issue: “The hot side of the mixing valve is very hot.”

Other commenters tried to determine whether the problem was limited to one fixture. When asked directly, the homeowner answered, “Both showers.” That suggested the issue was not a faulty showerhead or a single bad fixture.

More context

The boiler itself is about 30 years old, though the homeowner said a new combustion chamber was installed in 2014. They also said the mixing valve connected to the oil burner was replaced in 2018, meaning several important parts have already been changed without fully solving the weak shower issue.

One commenter said the tankless-coil design may itself limit how much hot water the system can provide. 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.”

The same commenter took the very hot pipe at the mixing valve as a sign that “it's an upstream issue,” adding 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 remaining repair would still appear to require a plumber.

Not everyone in the discussion thought replacing the coil would be a wise investment. One commenter said, “You can pay someone to swap the coil but at 30 years old you're wasting your time.” With both showers turning lukewarm, the homeowner is left weighing repair costs against the age of the equipment.

Possible next steps

Replies outlined several options depending on 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 issue is on the potable-water side, a licensed plumber in Connecticut would likely still need to inspect the coil and related components.

For homeowners who decide not to keep hot-water production tied to an aging oil boiler, Cala offers customizable smart heat pump water heaters designed to help reduce energy bills by heating water only when it is needed.

A smart heat pump water heater also gives homeowners another path instead of putting more money into a 30-year-old boiler. In this case, the next step may be comparing a coil repair, an indirect tank, and a separate smart water-heating system.

Related reading

These stories cover similar repair-or-replace decisions that come up with lukewarm showers and older water-heating systems.

• 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.