Solar Water Heater Problems and Troubleshooting Tips

Discover effective solutions for common solar water heater problems with our comprehensive troubleshooting guide. From solar panels and collectors to tanks and pumps, learn how to address issues such as leaks, low hot water temperature, lack of hot water, and low flow.

Additionally, we’ll provide essential tips on performing regular preventive maintenance to prevent water heating issues from occurring. Get ready to optimize your solar water heater’s performance and ensure consistent, reliable hot water supply.

solar panel for solar water heaters
photo: pixabay

Proper maintenance of your solar water heater involves thorough inspection of various components, including pipes, fittings, and solar panels, to identify potential leaks and degraded areas such as pipe insulation. Additionally, it’s crucial to check for corrosion on the tank and exposed surfaces, as well as perform routine tasks like flushing and draining the storage tank.

If the pipe insulation shows signs of degradation due to high temperatures, it should be replaced with a type that can withstand such conditions and constant exposure to UV rays.

To diagnose and address any issues with your solar water heater, it’s essential to have a basic understanding of the system’s type, components, functionality, as well as plumbing and electrical systems. The more knowledge you possess, the better equipped you’ll be to handle repairs. If you lack expertise in this area, it’s advisable to seek the assistance of a professional.

Before contacting a plumber for service, you may want to visit this website, where you can conveniently fill out a form and receive up to three free estimates from local plumbers. This allows you to compare options and make an informed decision.

Solar Water Heater Problems: Troubleshooting and Repair Tips

Solar water heater problems and troubleshooting guide is based on extensive online and offline research. It covers fundamental issues and provides easy-to-follow steps for successful repairs.

According to various studies, the most common problems encountered with solar water heaters are related to component failures, such as controllers, sensors, and pumps, rather than installation issues or lack of maintenance.

However, it is important to note that solar panels, being critical components, are not exempt from failures. They can experience problems such as broken panel glass, freezing, loose connections, and deterioration.

In the case of a defective controller or sensor, most technicians opt to replace the faulty element rather than attempting repairs.

Please be aware that while some problems can be easily identified and corrected, others may require more extensive work and knowledge. It may be necessary to examine multiple components, consider system design, and even assess the user’s lifestyle to diagnose and address certain issues.

Tip: To determine if the system is functioning correctly, try turning off the backup heat and assess the performance of the solar part. This simple test can help you evaluate the system’s functionality.

Common Problems in Solar Water Heating


  • If you notice water leaking from the roof when it’s not raining, the most common culprit is a faulty temperature and pressure relief valve on the heating system. It’s important not to attempt repairs on the T&P valve; instead, replace it with a new valve that has the same characteristics as the faulty one. Alternatively, you can replace the seal.
  • In the case of a leaking solar panel, it could be due to piping bursting from freezing or excessive pressure within the system. Before attempting any repairs or contacting a technician, isolate the panel by turning it off.
  • Check the piping fittings for any leaks, especially at the connections and during thermal expansion. Tighten any loose connections to address the issue.
  • Valves can also be a source of fluid leakage if the seat deteriorates or if the valve gland nut is loose. Replace the seat washer, tighten the nut, or consider replacing the entire valve. For instance, a freeze protection valve may require calibration or seal replacement.

Please note that if you encounter any glycol or water leaks, or experience a pressure drop in the glycol loop, it is recommended to contact your installation contractor to diagnose the problem and recharge the system.

Problems Caused by the Circulating Pump

Before proceeding with any repairs, always ensure to check the electrical connections, solar controllers, and the correct wiring and condition of the sensors. Make sure they are free from rust and deposits. To protect exposed areas, it is recommended to seal wire nuts with silicone. Additionally, inspect the sensor wires for any shorts or breaks, as well as check the circulating pump.

Note: On sunny days, the circulating pump should run most of the time, but on cloudy days, it may run less frequently.

  • If you notice that the circulating pump on your solar water heating system is constantly running or not running at all, it is possible that you have a problem with a faulty solar controller or an unplugged pump. The controller may have suffered damage due to voltage surges, short circuits, lightning, or corrosion.
  • If the controller is turned ON, but the pump won’t run, check if the pump’s impeller is blocked or seized. If there is debris obstructing the pump, clean it out.
  • If you observe periodic running of the circulating pump during the night, it could be due to water running through the system caused by temperature differences and a leaking lower valve. This phenomenon, known as thermosiphoning, can be resolved by replacing the check valve.
  • If there is no hot water when the circulating pump is running, it indicates that there may be trapped air in the pump collector of the solar heating system. Usually, the automatic air discharge valve located on the collector should allow the air to escape. If the air discharge valve is functioning correctly, purge the system by opening the pressure relief valve using your fingers.
  • In case you notice that your solar water heating system is making noise, it is possible that the pump bearings require lubrication.
  • Bearing failure is one of the most common problems, often occurring due to improper pump installation. Additionally, trapped air in the housing can affect water circulation.
  • If the pump fails to operate due to a locked-up impeller or damaged motor winding (burned-out motor), a pump replacement will be necessary.

Not Enough Hot Water

If you are experiencing issues with your hot water, such as insufficient or no hot water at all, consider the following possible causes for these solar water heater problems:

  • Check the orientation of the panels to minimize shading from trees. Ensure they are properly positioned to face south and tilted at the recommended angle. Also, verify if the panel size is adequate. Clean any dirty glazing. Evaluate if excessive hot water usage could be a contributing factor.
  • A leaking or stuck check valve can lead to problems like insufficient hot water. Additionally, if the storage tank has a backup heating element, ensure its thermostat is not set too low or that the element is functioning correctly.
  • To prevent solar panels from freezing during winter, ensure there is a slope on the collector, with the output end positioned higher. Proper drainage should help resolve this issue.
  • Check for low system pressure or any flow blockages. Examine the pressure gauge and flush the system if there is a blockage affecting the flow.
  • If the hot water is not reaching the desired temperature, it indicates heat loss in the solar water heating system. Provide appropriate insulation for the storage tank, including an insulation blanket if necessary. Insulate the pipes and seal all joints and connections.
  • If there is insufficient hot water in the morning, check if the sensor wires are reversed and reconnect them correctly if needed. Additionally, inspect the sensors and controllers for any faults, ensure connections are secure, and check for any shorted sensors. Always refer to the system schematic, verify the wiring, and clean and seal any exposed areas.
  • Insufficient tank size, high energy losses in the storage tank, and backup heating not working efficiently during periods of low solar efficiency (such as at night or on cloudy days) can all contribute to problems.
  • Consider replacing corroded piping, flushing mineral deposits to remove blockages, adding insulation as necessary, and ensuring isolation valves are open.

No hot water

Take a look at the auxiliary heater or mixing valve as it may be the source of the problem. If it is an electric heater, check if there is power reaching the heating element. In case of a defect, consider replacing the heating element or thermostat. If it is a gas heater, consult this troubleshooting guide for assistance.

Solar Panel Problems

  • The primary issue with solar panels is broken glass. There are two possible solutions: replacing just the glass or replacing the entire solar panel. However, both options can be costly. When replacing the glass, ensure that you order strong, tempered glass of the correct size for a proper fit.
  • If the absorber paint or coating deteriorates, you may consider repainting it. It is important to choose paint with excellent heat and UV resistance properties specifically designed for this purpose.
  • Condensation on the panel glass over time can lead to water accumulation at the bottom of the panel, affecting its efficiency and performance. To address this problem, it is recommended to provide a small weep hole at the bottom of the collector.
  • If the panel glass feels hot to the touch, it indicates high heat loss from the absorber and reduced solar panel efficiency. Possible causes of this issue include water passage obstructions due to scale buildup, improper pump operation, undersized pump, or connection disruptions.

Problems With the Noisy Water Heater

The knocking noise in the storage water tank is a problem that occurs when the solar high limit control is set too low. Additionally, when the sun is still shining outside, the pump turns off, causing water in the panel pipes to boil and send steam into the water tank.

The solution to this issue involves either adding a water tank or installing a tempering valve to limit the water temperature. Another option is to set the high limit control higher and install a controller that will force the pump to run for a longer duration, thereby cooling the tank down.

Freeze Damage

Freeze damage can occur to any solar water panel, regardless of whether the system is drained or not, or if the operating fluid has a low freezing point (such as water).

Freezing may still occur even if the collector is drained, as there could be trapped water in the system. If the freeze protection system fails, the sensor freezes, or no freeze protection valve is installed, freezing can still happen.

Additionally, even if the isolation valve was installed and closed, mineral deposits or element failure could cause the valve to leak, allowing water to reach the collectors and resulting in frozen collectors and pipe rupture.

Sediment Buildup

Sediments in solar water heating systems can be caused by various factors. Here are some common causes:

  • Hard water: Hard water contains high levels of minerals such as calcium and magnesium. Over time, these minerals can precipitate and form sediments inside the solar heating system. The minerals settle in the bottom of the storage tank and can also accumulate in the pipes and heat exchanger, hindering heat transfer and reducing system efficiency.
  • Corrosion: Corrosion occurs when the metal components of the solar heating system come into contact with oxygen and water. The corrosion process can create rust particles that contribute to sediment buildup. Corrosion can be accelerated by factors such as low pH levels in the water, high levels of dissolved oxygen, or inadequate corrosion protection measures.
  • Pipe degradation: In some cases, the interior of the pipes in a solar heating system can degrade over time. This can occur due to factors such as water chemistry, high temperatures, or the use of incompatible materials. Degraded pipe materials can release particles into the water, leading to sediment formation.
  • Water supply issues: Sediments can enter the heating system through the water supply. If the water source contains sediments or debris, they can get carried into the system, particularly if there is inadequate filtration or water treatment in place.
  • Improper installation or maintenance: If the solar heating system is not installed correctly or not maintained regularly, it can contribute to sediment accumulation. Poorly designed plumbing connections, improper flushing procedures, or neglecting system maintenance can lead to sediment buildup over time.
  • Environmental factors: External environmental factors such as dust, leaves, or other debris can find their way into the solar heating system, especially if there are any openings or leaks. These particles can settle in the storage tank or other components and contribute to sediment formation.

To minimize sediment accumulation, it is important to address these causes. Regular maintenance, including flushing the system, inspecting and cleaning the components, and implementing appropriate water treatment measures, can help prevent or reduce sediment buildup in the solar heating system.


Solar water heaters can last for 20, 30, or even more years with proper maintenance and servicing. However, if the panels have been installed and sitting on the roof for an extended period, normal wear and tear may require closer inspection, replacement, or upgrades of certain components.

Troubleshooting solar water heater problems can be challenging, complex, and expensive for individuals. If you are unable to find solutions for the issues with your solar water heater and require estimates for installation or troubleshooting, please fill out the request form here.

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