Solar Water Heaters Problems and Troubleshooting

How to repair problems like leaking, low hot water temperature... in solar water heating

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Use the solar water heaters problems and troubleshooting guide to fix problems on solar panels and collectors, solar tanks and pumps, including leaking, low hot water temperature, insufficient supply, low flow...

For any troubles you have with the solar water heating, recommendation is to use the preventive maintenance to keep the thermal performance on the high level and avoid problems on the system and components.

The maintenance will include the regular inspection of pipes and solar panels for possible leaks, degraded areas, corrosion on the tank and exposed surfaces, flushing and draining the solar storage tank.

Problems and troubleshooting guide

Solar water heating systems are not complicate. If it fails, the odds are that the problem is with the solar panel, tank or the pump. We research and find the most common problems, using the online and offline resources and show you how to solve them using this solar water heaters problems and troubleshooting guide.

To determine what is the problem with your solar water heating system, first turn the backup heater OFF by shutting off the electric power or gas supply. In order to see is the heating working or not, there should be lots of sun, and collectors should be exposed to the sunlight for the full day. If you didn't feel any heat on the outside surface of the tank or there is a shortage of hot water, you are experiencing a problem with the heating system.


  • If you find the water is leaking from the roof (and it is not raining) the most common cause is the leaking temperature and pressure relief valve on the solar heating system. Do not try to repair the T&P valve; replace it with the brand new valve which will have the same characteristics as the faulty one.

  • Solar panel might be leaking if the panel bursts due to freezing or the excessive pressure within the system. Before you do any repairs or call the technician, isolate the solar panel by turning it off.

  • Check out the piping fittings, it might leak there during the thermal expansion. Tighten the loosened connections.

  • Valves can also be the cause of the fluid leaking when the seat deteriorates or if the valve gland nut is loose. Replace the seat washer, tighten the nut or simply replace the whole valve.

Note: For any glycol or water leak, or glycol loop pressure drop, recommendation is to call your installation contractor to diagnose the problem and recharge the system.

Problems caused by the circulating pump

Before you do any repairs always check the electrical connection, solar controller and are the sensors properly wired and free from the rust. This is why the exposed areas should be protected, i.e. wire nuts should be sealed with the silicon. Check also for the shorts and breaks in the sensor wires or circulating pump.

  • If you find that the circulating pump on your solar water heating systems is running all the time, or it won't run at all, you might have the problem with the faulty solar controller or the pump is not plugged into it.

  • If the solar controller is ON but the pump won't run, you should check is the pump impeller blocked. If there is debris blocking the pump, clean it.

  • If the circulating pump runs periodically during the night, you might have a water running due to the temperature difference inside the system and leaking lower valve. This is called thermosiphoning and one of the solutions might be to replace the check valve.

  • If there is no hot water when the circulating pump is running, solar heating system has the air trapped in the pump collector. Usually, the automatic air discharge valve located on the collector should allow the air to escape. In a case if the air discharge valve is working properly, purge the system by opening the pressure relief valve with your fingers.

  • If you find that the solar water heating system is noisy it might be that the pump bearings need lubrication.

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Not enough hot water

If you have a problem with the hot water, like not enough or no hot water at all, here are the possible causes for these solar water heaters problems:

  • Solar water heater problems like not enough hot water available are usually caused by the leaking or stacked check valve. Also, if the solar storage tank has the backup heating element, its thermostat might be set too low or the element is gone.

  • To avoid solar panels to freeze during the winter time, always provide a slope on the collector so the output end is higher. The proper drainage should solve the problem.

  • Did you check for the low system pressure or flow blockage? Check the pressure gauge or flush the system if the flow is blocked.

  • If the hot water is not hot enough, your solar water heating system is losing the heat. Provide the proper insulation to the storage tank, include the insulation blanket if needed, insulate the pipes, seal the pipe, tank and all the joints.

  • If there is not enough hot water in the morning, check are the sensor wires reversed. Connect them properly if they are. Also, check for the faulty sensors and controllers, loose connections and shorted sensors. Always use the system schematic, check the wiring, clean and seal exposed areas.

  • Check for the solar panel orientation to reduce the shading, orient it properly to face south, provide the recommended tilt. Is the panel size sufficient? Clean the dirty glazing.

  • Problems with the tank will include the insufficient size, high storage losses, backup heating is not working when solar is not efficient (during the night, cloudy days...)

Troubleshooting solar water heaters problems is easier when you share the problem with us. Our goal is to provide the answer. If you are not able to find the answer for your solar water heaters problems here, use the link to ask or find the solution.

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