Apollo Water Heater Troubleshooting

The Short Answer: “Apollo” appears on several different products around water heaters, so start with the label. On an air handler that uses your water heater for home heating, decide whether the heater or the air handler’s pump and coil is at fault. On a brass valve near the heater, it may be a mixing valve. On the tank itself, troubleshoot it like any gas or electric tank.

Find out what the Apollo label is on

Take a photo of every label in the area: the water heater’s rating plate, any air handler, and any brass valves on the pipes above the heater. Then match what you have:

If the rating plate lists a different manufacturer, use that manufacturer’s documents for parts and codes. Our guide to identifying your water heater shows where to look.

Combination systems: heater or air handler?

In a combination system, the water heater serves both your taps and the air handler. A pump moves hot water from the heater through a coil in the air handler when the thermostat calls for heat. That gives two quick tests:

• Taps hot, house cold. The heater works. The problem is in the heating side: the pump, air trapped in the loop, the coil, the air handler’s blower or filter, or the controls.
• Taps cold and house cold. The water heater itself has stopped. Check it as described below.
• Taps lukewarm, house warm. Look at a mixing valve or the heater’s capacity; the heater may be supplying both loads at once.

Owner checks for the air handler: confirm the thermostat is calling for heat, replace a dirty air filter, and check the air handler’s power switch and breaker. Bleeding air from the heating loop and pump repairs are a heating technician’s job.

Mixing valves: lukewarm water with a hot tank

A thermostatic mixing valve blends cold water into hot to limit the temperature at the taps. If the pipe going into the valve from the heater is hot but every tap is lukewarm, the valve setting or its cartridge is the likely cause, not the heater. Ask a plumber to adjust or service the valve. Turning the heater up to compensate can lead to scalding if the valve later fails. Related: apartment water heater not hot enough, which covers the same lukewarm patterns.

Basic tank checks

Gas tank: confirm the gas supply valve is on and other gas appliances work, check the status light or pilot through the viewing window, and relight once following the label if the pilot is out. A pilot that will not stay lit is covered in why a gas water heater won’t stay lit.

Electric tank: check that the double-pole breaker is fully on. If hot water runs out quickly, a failed lower element is common; see water heater element not working. Element and thermostat testing is done by a technician with power isolated.

Any tank: water around the base needs tracing to its source before you assume the tank has failed. Relief valve discharge, fittings, and condensation are more common than a tank leak.

What the technician will check

On a combination system, a heating technician checks the pump and its relay, purges air from the loop, and confirms the coil heats and the blower runs. For mixing valves, a plumber checks the inlet and outlet temperatures and the valve cartridge. For the tank, the technician follows the manufacturer’s procedure for the fuel type, including gas pressure and ignition checks or element and thermostat tests.

Frequently Asked Questions

Q: Can a water heater for a combination system be replaced with any tank? A: The replacement must be approved for combination space and water heating and sized for both loads. A technician should match it to the air handler’s requirements.

Q: Why did my hot water get worse after the heat came on for winter? A: In a combination system, the air handler draws heat from the same tank. During long heating cycles, less hot water is left for the taps. A technician can check whether the heater is sized for both.