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Common Problems With Solar Hot Water

If you’re experiencing problems with your solar hot water system, you are not alone. Although they are a great, eco-friendly way to heat your home’s water supply, solar hot water systems are prone to a few common problems for owners all over the world.

Whether you are weighing your purchasing options or currently dealing with an issue of your own, we’ve developed this guide to help you understand some of the most common problems with solar hot water systems. After a look at some of the most common problems and solutions for real-life issues, we will answer some frequently asked questions for Australians. 

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Parts of a Solar Hot Water System 

But first, let’s bring you up to speed to understand all of the parts of a solar hot water system. Knowing the names and functions of each piece of equipment will make it much easier to understand where, why, and how your system may be experiencing problems. 

Thermal Solar Collectors 

On top of your roof or out in the yard, the thermal solar collectors capture the heat of the sun and transfer it to your home’s hot water. Thermal solar collectors come in two basic forms: flat plate panels and evacuated tube cylinders

Flat plate collectors more closely resemble PV solar panels, whereas evacuated tube thermal solar collectors appear as a series of tubes with water or antifreeze liquid running through the rooftop pipes. 

The Water Supply Tank 

While your solar collectors make generating energy possible, the water supply tank is the most important component of an effective solar hot water system. Installed either on your roof or in another location on the property, a solar hot water tank requires significant insulation to keep your water warm at night when the sun’s rays are unavailable. 

Heat Exchanger / Heat Transfer System 

In order for the energy of the sun to reach the water tank, active solar hot water systems use a heat exchanger (also known as a heat transfer system) to accomplish the task. For most efficient home systems, the heat exchanger is a network of pipes and parts that sends hot antifreeze liquid through the water tank via a heat-emitting pipe.  

Circulation Pump 

To keep the whole thing running, the circulating pump (or circulation pump) helps control your system’s flow with adjustments on the property’s hot and cold water lines. The circulation pump begins by sending hot water from your system to your tank and faucets, while also pumping cold water from the bottom of the supply when necessary to balance temperatures.  

External Boost

When there is not enough solar energy to meet a property’s hot water demand, an external boost can automatically or manually keep the system running with gas or electric power. Hooked up to utility lines or a personal energy generating system, the boost is a necessary part of a solar hot water heater for those in variable climates and sun conditions. 

Common Problems with Solar Hot Water Systems 

Before we dive in, it is important to know that solar hot water systems do not contain many moving parts and are therefore generally very durable, reliable, and problem-free. With that said, old worn components, shotty installations, regular service neglect, and even unpreventable accidents may cause any of the following problems.  

Here are the most common problems users may experience:

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1. Clogged Pipes from Sediment Build Up 

As one of the most common plumbing problems in a home, clogged pipes from sediment buildup is often the underlying cause of a solar hot water system’s deterioration. Over time, sediment, dirt, and debris build-up within the pipes of a system will cause blockages. Without a clear path, your heater will need to work harder and will therefore be less efficient overall.

If you suspect that there may be sediment build-up in your solar hot water system, clearing the pipes of debris will instantly increase its efficiency in addition to prolonging the overall lifespan. To achieve this, It may be possible to flush your sediment out with a special cleansing product after taking all of the necessary safety precautions.

While sediment build-up is covered in most system warranties, regular maintenance check-ups are a great way to prevent the problem from ruining your hot water components before it’s too late. With this in mind, sediment is typically only an issue for neglected or unmonitored systems.  

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2. Component Corrosion, Scaling, and Deterioration 

Second to sediment build-ups, long-lasting solar hot water systems may be subject to component damage from corrosion, scaling, and general deterioration. If the water in your home is exceptionally hard, calcium deposits may build up in your system’s components causing leaks, failures, and losses in efficiency.

To prevent this, a mild, acidic cleaning agent can be pumped through your system’s pipes approximately every 3 to 5 years. Alternatively, a water softening solution can also be used to independently lower your home’s water hardness.

On the other hand, rusting may be caused by oxygen entering into your hot water system, and components made of iron or steel should be avoided for this reason. Although solar hot water systems are intentionally designed to minimize corrosion, damage from galvanic corrosion may occur if multiple kinds of metal interact over time.  

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3. Water or Heat Transfer Fluid Leaking

As a true “worst-case scenario,” it is not unheard of for solar hydronic systems to begin leaking water or heat transfer fluid. In the image above, you can see deterioration and leaking from a solar thermal collector, with obvious damage to the system hardware.

In instances such as this, it is critical to call a professional to fix the problem as soon as possible. Almost always, the first step that they will recommend will be to turn off the system entirely with the installed safety switch. From here, you mustn’t try to repair the leak yourself, with the risk of damaging the system components and voiding your warranty. 

Fluid leaks may occur anywhere in the system, from leaky collectors on the roof, to the piping, to the heat exchanger and water storage. In most cases, components can be repaired without the need for total replacement. However, if leaks are sprung early on in a system’s lifespan, defective parts under warranty should be replaced to lessen the chance of another issue.  

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4. Freezing and Other Pipe Damages

As many homeowners have learned the hard way, freezing and damages to pipes within a home can be disastrous in unforeseen circumstances. To prevent this from happening, hydronic solar water heaters utilize an antifreeze heat transfer fluid, however, those that use exclusively water are much more likely to accumulate damages from freezing temperatures.

In a fully water-based system, components can be set to drain automatically to prevent water from sitting in pipes, ready to freeze and burst. Today, many advanced systems come with built-in “freeze sensors” that will automatically deploy the necessary actions to prevent cold weather damage. 

For leaks from freezing, valve damage, and more, we strongly suggest turning off your system and calling a professional as quickly as possible. Before you start to clean up the mess, don’t forget to take some pictures if you’ll be filing an insurance claim. 

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5. Not Enough Hot Water or No Hot Water At All 

If your hot water supply has suddenly dwindled below its normal operating rates, the cause may be one of many things.  After fully inspecting your entire system for leaks, breakages, ware, and other damage, you may need to call in a professional if the problem cannot be identified.

As systems slowly lose efficiency over time, homes with increased hot water demand (i.e. new dishwasher or an extra person in the home) may also naturally outgrow their solar hot water heater. It may be possible to upgrade your tank or add extra solar collectors to get more hot water in an existing system.

When your solar hot water is not working whatsoever (including issues with the boost), there is most likely a broken auxiliary valve or other large problem. After ensuring your system is set for normal operation, call a licensed solar hot water technician to help find a solution.  

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6. Infestations 

Although they are less frequent than other common problems with solar hot water heaters, infestations can happen and have the possibility of being devastating when they occur. In the image above, you can see that a colony of ants has made their home in a hot water heater, which has complicated things for the system’s efficiency. 

While it is easy to say that annual inspections may have prevented this, a problem such as an ant infestation may also require you to make a call to pest control before sorting out your solar hot water problem. 

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7. Noisy Heaters and System Components

Finally, a loud solar hot water heater can make it very unpleasant for those nearby. As the technology gets more efficient and optimized for home use, solar hot water heaters have gotten quieter over the years, but this does not mean that modern systems cannot occasionally cause a racket. 

If you’re experiencing noise problems with your solar hot water heater, you may need to add a tempering valve or new solar hot water controller, each of which requires a professional installation.  

How to Fix A Solar Hot Water Problem

As you may have noticed while learning about some of the most common problems with solar hot water systems, the many paths to fixing various issues generally follow the same formula.  In fact, fixing a solar hot water problem is as easy as one, two, three.  

Step #1: Identify the Problem 

First, identify the issue. If your problem is simply not having enough hot water, then you can jump straight to step three. Conversely, if there is an active leak, visible damage, or unbearably loud or poor performance, then please proceed to step two. 

Step #2: Turn Your System Off and Address Pressing Issues 

Next, turn off your system’s water, electrical, and gas components. This includes powering down the system as indicated in your instruction manual as well as turning all of the inlet and outlet valves to an off position. If any damage has occurred to your property, be sure to take photos and work to create a safe environment around the problem. 

Step #3: Troubleshoot the Problem or Call a Professional

Once you have identified the issue and turned off your system, we recommend calling a professional 9 times out of 10. Unless you are an experienced hot water operator, you will be much more likely to enjoy an efficient fix under your system’s warranty by having a professional contractor look at the issue. 

Preventive Measures for Common Solar Hot Water Problems 

Of course, the best way for the solar hot water problem to be fixed is for them to have never happen in the first place. While we are not asking you to set aside the majority of your brainpower for your solar hot water heater, a little bit of attention can go a long way for the health and ongoing performance of your system.  

Monitoring system performance: If your solar hot water system includes a performance monitor, take a moment to learn about all of the numbers on the digital display. Understanding what “normal” operations look like for your system is the best way to know if and how things have changed when things go wrong.

Regular servicing: Prevent common problems with solar hot water heaters by keeping up to a routine servicing schedule. While you should personally check on your system once or twice per year, a full professional servicing is recommended every 5 years or so.

Responsible use: While we fully understand the necessity of a hot shower, irresponsible solar hot water use may cause damage to careless owners. For the ongoing health and wellness of your system, be sure to set your home’s hot water at reasonable temperatures and minimize the amount of boosting necessary to meet the property’s demand. 

Frequently Asked Questions 

And finally, we’d like to clarify a few specific answers to some of the most frequently asked questions regarding common solar hot water problems.  

How can you tell if your solar hot water is working? 

If you have a booster-assisted heating system, it can be difficult to tell whether or not your solar input is responsible for the poor performance. Oftentimes, this is found out way too late after the previous month’s utility bill indicates significant gas or electric usage.

To quickly verify whether or not your solar hot water is working, you must check your system’s switchboard. If the boost switch has been left in the “on” position, simply flip it back to “off” to resume solar power. If you do not have hot water after this, then there is an issue with your collector or heating system. 

How do I reset my solar water heater?

Although the actual method will vary between makes and models, most solar water heaters can be reset with the simple flip of a switch or push of a button. If this feature is not included in the system hardware, consult your owner’s manual. In most instances, a hard reset for solar water heating systems requires a licensed electrician, plumber, or specialty contractor. 

Does solar hot water stay hot overnight?

Yes! Primarily the responsibility of the tank’s insulation, solar hot water heaters are specifically designed to generate tons of heat during the day and keep it stored safely and ready to use throughout the night. Most solar hot water heaters would not be practical for home or business use if it was not for this. 

Do all solar hot water systems have a booster?

No, not all solar hot water systems include a booster, but almost all practical solutions for Australian homes do. Whether powered by gas or electricity, boosters are entirely necessary for homes to maintain consistent and reliable hot water through cold winters or prolonged absence of sufficient solar power. 

How long does solar hot water take to heat up?

The amount of time it takes a solar hot water heater to heat up depends on the size of the tank, the amount of solar input, and the overall system efficiency. From room temperature to shower-friendly, most solar hot water heaters can sufficiently warm up an entire residential tank in as little as two to three hours. 

Why is my solar hot water not getting hot enough?

There are many different reasons why your solar hot water heater may not be providing enough heat for your home. While each issue has its own way to diagnose and solve, some of the most common reasons for less than ideal temperature include:

  • Long periods of clouds or low sunlight
  • Panels have accumulated dust and debris
  • Tank or other components are not sufficiently insulated 
  • The system is unable to keep up with the home’s hot water demand
  • And more

Are solar hot water panels worth it?

While everyone’s situation is going to be slightly different, solar hot water panels are worth it for most Australians. Not only can systems be purchased with widely available solar hot water rebates, but the endless free energy of the sun can also help homes and businesses alike save heaps of money for the long-term costs of hot water. 


And that’s a wrap! We hope that this guide has helped you learn more about some of the most common problems with solar hot water systems. Although we hope that your particular system lives a long, problem-free lifetime, it is always good to understand the most common issues and know what to do when they arise. 

If your system is no longer worth its weight in metal, you may want to consider purchasing a new heater entirely. For a bit of inspiration, check out our guide to the best solar hot water systems in Australia.