Solar Thermal Repair
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Stop overpaying for hot water from a system that is not working as it should.
A solar thermal system is one of the smartest investments a homeowner or commercial property owner can make. When it runs correctly, it uses free energy from the sun to heat your water, reducing the workload on your boiler and cutting your energy bills month after month. When something goes wrong, those savings stop, your boiler compensates for the shortfall and the underlying fault nearly always gets worse the longer it is left.
At Solar Maintenance And Repairs, we provide specialist solar thermal repairs for properties across Hampshire and South England. Our engineers are NAPIT-registered, TrustMark-endorsed and work exclusively within the solar industry. That means when we arrive at your property, we know solar thermal systems in depth, not as an add-on to a broader heating or electrical service, but as the core of what we do every day.
We repair all types of solar thermal systems, including flat plate collector systems, evacuated tube collector systems and drain-back configurations. Whether you are dealing with pressure loss, a circulation pump failure, degraded heat transfer fluid, a faulty controller or collector damage, we diagnose the fault accurately and repair it correctly so the problem does not come back.
If your solar thermal system is not performing as it should, call us today on 0330 111 9399 or request a free quote online.
The Financial Benefits of Repairing Your Solar Thermal System Early
Every day a solar thermal system runs below its designed performance is a day your boiler or immersion heater works harder than it needs to. The energy savings a properly functioning solar thermal system delivers are not trivial. A well-sized system on a typical UK home can contribute a significant proportion of annual hot water demand, particularly through the spring, summer and autumn months. When the system underperforms due to a fault, that contribution drops and your energy bills rise to compensate.
There is also the compounding effect of unresolved faults to consider. Degraded heat transfer fluid does not just reduce efficiency in isolation. Over time it becomes acidic and begins to corrode the internal surfaces of the system, causing damage that extends well beyond the original fault. A failing pump that is not replaced draws excess electricity and accelerates wear on surrounding components. Small problems that are inexpensive to fix at the point they develop can become considerably more costly if left unattended.
Professional repairs by a qualified specialist also protect your system’s longevity. Solar thermal systems are designed and manufactured to last 20 to 25 years. That lifespan is only achieved when faults are identified and resolved correctly. A system that has been running with degraded fluid, incorrect pressure or a partially failed pump for an extended period will not reach that potential lifespan, regardless of how good the original installation was.
The other key reason to use a qualified specialist rather than a general heating engineer is accurate diagnosis. Solar thermal faults often present with similar symptoms despite having different root causes. Low output from the system could indicate a pump issue, an air lock, depleted fluid, a sensor fault, a collector problem or a combination of several factors. Treating the wrong cause wastes money and leaves the real problem in place. Our engineers carry out a full system diagnostic before any repair work is recommended, so you know exactly what is wrong and what fixing it involves.
Signs Your Solar Thermal System Needs Professional Attention
Not every solar thermal fault causes an immediate and obvious failure. Many develop gradually, reducing performance over weeks or months before becoming impossible to ignore. The following signs indicate that your system needs a professional inspection and repair.
- Your hot water cylinder is not reaching temperature on bright, sunny days
- The system pressure gauge is reading outside its normal operating range
- The controller is displaying a fault code or behaving unusually
- The circulation pump is running continuously, not running at all, or running at odd times
- You can hear unusual noise from the pump or pump station
- There is visible fluid leakage from any part of the system
- You can see condensation or discolouration behind the glazing of a flat plate collector
- Individual evacuated tubes are cold when the rest of the array is warm and running
- Your hot water costs have increased without any change in usage patterns
- The system has not been professionally inspected within the last two years
If any of these apply to your system, the right course of action is to arrange a professional inspection sooner rather than later. The earlier a fault is identified, the less damage it causes and the less it typically costs to resolve. Contact our team to arrange a diagnostic visit at a time that suits you.
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Common Solar Thermal System Problems We Repair
Solar thermal systems share a set of faults that our engineers encounter regularly. Each has a defined cause, a clear diagnosis process and a reliable repair solution. Understanding what can go wrong with a solar thermal system helps you recognise the signs early and act before a minor issue becomes a significant one.
Degraded Heat Transfer Fluid
The heat transfer fluid in a solar thermal system, typically a propylene glycol and water solution, does not last indefinitely. It degrades over time, and the process accelerates in systems that regularly experience stagnation, which is the state the system enters when the cylinder is fully charged and there is nowhere for the heat being generated by the collectors to go. During stagnation, fluid temperatures in the collectors can reach extremely high levels. Over repeated cycles, this breaks down the glycol chemistry, causes the fluid to become acidic and reduces its ability to transfer heat efficiently. It also strips away the frost protection properties, increasing the risk of frost damage in winter. Most manufacturers recommend the heat transfer fluid is checked and replaced every four to five years. If yours has not been attended to within that window, it is one of the most common and most impactful repairs we carry out.
Circulation Pump Failure
The circulation pump moves the heat transfer fluid from the roof-mounted collectors down to the heat exchanger coil in your hot water cylinder and back again. If the pump fails, heat generated in the collectors has no way to reach the cylinder, and the system effectively stops working even on the sunniest days. You will typically see the collectors reaching very high temperatures while the cylinder temperature stays flat. In some cases a failing pump makes unusual noise before it stops completely. Pump replacement is one of the most straightforward and common solar thermal repairs, and in the vast majority of cases it is completed on a single visit.
System Pressure Loss
A solar thermal system is a sealed, pressurised circuit that operates correctly only within a defined pressure range. If you notice the system pressure gauge reading lower than usual, or if the system pressure keeps dropping after being topped up, there is an underlying cause that needs to be identified and fixed. The most common causes are a failed expansion vessel, a leak in the pipework or connections, or a relief valve that has discharged. Simply re-pressurising a system without addressing the cause of the pressure loss will not resolve the problem. Our engineers trace the source, carry out the necessary repairs and restore the correct operating pressure.
Controller and Sensor Faults
The differential temperature controller is the component that decides when the pump runs. It reads temperature sensors at the collectors and at the bottom of the cylinder, and when the collectors are significantly hotter than the cylinder, it activates the pump to transfer heat. When the controller or one of its sensors fails, this logic breaks down. The pump may run when it should not, fail to run when it should, or behave erratically. Any of these conditions directly reduces performance and can cause unnecessary wear. Controller and sensor replacements restore the correct operating logic and are typically completed within a single visit.
Air Locks in the Circuit
Air trapped in the pipework or collector circuit prevents the heat transfer fluid from circulating properly. Even a partial air lock significantly reduces the system’s ability to move heat from the collectors to the cylinder. Air locks are most common after a fluid replacement, following a repair where the system has been drained, or after an extended period of stagnation where the fluid has partially vaporised. They require careful purging at the correct air bleed points to restore full, uninterrupted circulation.
Collector Faults
The collectors themselves are subject to specific faults depending on whether you have flat plate or evacuated tube panels. In flat plate collectors, the glazing seals can deteriorate over time and allow moisture to enter the sealed unit. Once moisture is present inside a flat plate collector, condensation forms on the glass, reducing the amount of sunlight reaching the absorber and progressively damaging the absorber surface. In evacuated tube systems, individual tubes can fail. When a tube fails it becomes cold while the rest of the array is warm and active. Failed tubes can be identified and replaced individually without replacing the entire collector assembly. Both types of collector fault are diagnosable and repairable in most cases without the significant cost of a full collector replacement.
Frost Damage
Solar thermal systems in the UK are designed to operate safely through typical winter temperatures, provided the heat transfer fluid is mixed at the correct glycol concentration for the prevailing frost risk. If the fluid has degraded or been diluted over time without the glycol ratio being corrected, the frost protection threshold rises and the system becomes vulnerable during cold snaps. Frost damage can affect pipework, pump housings, collector manifolds and connection points. An inspection following a hard frost allows any damage to be identified and repaired before it causes further deterioration.
Our Solar Thermal Repair Process
Every solar thermal repair job we carry out follows the same structured process. This consistency is how we ensure that faults are correctly identified, repairs are completed to a high standard and your system is left working reliably before we leave site.
Initial Contact
When you get in touch, we take time to understand your system and the problem you have noticed. We ask about the type of system you have, how old it is, what symptoms you are seeing and whether any fault codes are displayed. This information means our engineer arrives prepared, with the diagnostic tools and the most likely required parts already in the van.
On-Site Diagnosis
Our engineer carries out a full diagnostic inspection of your solar thermal system. This covers the collectors on the roof, the pipework inside and outside the property, the pump station, expansion vessel, controller, sensors and the hot water cylinder connections. We check system pressure, assess the heat transfer fluid, observe pump operation and review the controller behaviour. After the inspection we explain our findings clearly and provide a transparent, itemised quote for the repair work required. Nothing is started without your agreement.
Repair
We carry out the agreed repair work using the correct parts and materials for your specific system. We work carefully, particularly around roof-level access and connections to your hot water system. All work is completed to current industry standards, and we do not cut corners on materials or workmanship.
System Test and Recommissioning
When repairs are complete, we test the full system to confirm that the fault has been resolved and that everything is operating correctly. This includes checking system pressure, verifying correct circulation throughout the circuit, confirming the controller is activating the pump at the right temperature differentials and monitoring the system through an initial operating cycle. We do not leave until we are satisfied the system is working as it should.
Handover
We provide clear documentation of the work completed and flag anything we have observed during the visit that may require attention in the future. You leave the visit with a full picture of your system’s condition and a record of the repairs carried out.
Why Choose Solar Maintenance And Repairs?
Solar Maintenance And Repairs is a dedicated solar specialist. We do not offer solar thermal repair as a sideline to a broader heating or electrical business. Solar energy systems are our entire focus, which means our engineers develop a depth of practical knowledge that a generalist contractor simply cannot replicate. We know the differences between system types, between collector brands, between controller generations and between the various configurations installed across UK properties over the past two decades. When something goes wrong with your solar thermal system, that specialist knowledge leads directly to faster, more accurate diagnosis and more effective repairs.
We are NAPIT-registered and TrustMark-endorsed, two accreditations that reflect our commitment to quality workmanship and recognised industry standards. Our ratings on Checkatrade and Trustpilot are consistently strong, reflecting the standard of work and service our customers receive across every job. We are also members of the Federation of Small Businesses, and we are proud of the trust we have built with residential and commercial customers across Hampshire and South England over the years we have been operating.
Every repair begins with an honest, transparent diagnosis. We tell you exactly what is wrong, what fixing it involves and what it will cost before we start any work. We do not carry out additional work without your agreement, and we do not charge for work you have not approved. This straightforward approach to pricing and communication is something our customers repeatedly highlight in their reviews, and it is central to how we operate.
We also offer a full range of related services that goes well beyond solar thermal repairs. If you need ongoing solar thermal maintenance, solar PV repairs, solar PV maintenance, commercial solar servicing or help with battery storage, we can provide all of it under one relationship. For customers with both solar thermal and solar PV systems, this means a single, trusted specialist for everything solar-related on your property.
Book Your Solar Thermal Repair Today
If your solar thermal system is losing pressure, failing to heat the cylinder, displaying fault codes or simply not performing the way it should, do not leave it to get worse. A fault that is inexpensive to fix today can become a much more significant problem over time, both in terms of the repair cost and the energy you are losing while the system underperforms.
Solar Maintenance And Repairs provides professional, specialist solar thermal repairs across Hampshire and South England. Our process is simple. Call us on 0333 004 7969 or email info@solarmaintenanceandrepairs.co.uk, tell us about your system and what you have noticed, and we will arrange a diagnostic visit at a time that suits you. After the inspection we provide a clear, itemised quote with no obligation to proceed. If you are happy with the quote, we carry out the repair, test the system fully and hand it back to you working correctly.
Frequently Asked Questions
The most common indicators are a hot water cylinder that is not reaching temperature on sunny days, a pressure gauge reading outside its normal range, fault codes on the controller display, unusual pump noise, visible fluid leaks or higher energy bills without any change in usage. If any of these apply, arranging a professional diagnostic inspection is the right course of action. Many faults are straightforward to resolve when caught early, but they become more costly and complex if left unattended.
The majority of solar thermal repairs, including pump replacements, fluid services, controller replacements and expansion vessel work, are completed within a single visit. More complex faults or jobs that require parts to be ordered may require a follow-up appointment, but we aim to resolve most issues on the same day wherever possible. We tell you at the diagnostic stage whether your repair is likely to be completed in one visit.
Yes. We work on all the main types of solar thermal systems installed across UK properties, including flat plate collector systems, evacuated tube collector systems and drain-back configurations. We also have experience across the various controller brands, pump station types and cylinder configurations used in UK installations over the past two decades. If you have an older or less common system, please call us on 0330 111 9399 and we will confirm our ability to help before booking a visit.
Most solar thermal manufacturers recommend the heat transfer fluid is tested and replaced every four to five years. The fluid is a propylene glycol solution that degrades over time, particularly in systems that regularly experience stagnation during hot weather. Degraded fluid loses its heat transfer efficiency and its frost protection properties, and it can become acidic, causing internal corrosion. If your system has not had its fluid checked within this window, we would recommend arranging a service visit.
Repeated pressure loss on a solar thermal system almost always indicates an underlying fault that needs to be identified and fixed. The most common causes are a failed expansion vessel, a leak in the pipework or connections, or a relief valve that has discharged due to the system running at excessive pressure. Simply topping up the pressure without addressing the root cause will not resolve the problem. Our engineers carry out a full pressure circuit inspection, identify the source and carry out the appropriate repair to restore and maintain correct operating pressure.
In most cases, yes. Solar thermal systems are designed to last 20 to 25 years with proper maintenance and timely repairs. Many of the systems we repair are 10 to 15 years old and, once repaired, will continue delivering strong performance for many more years. Whether a repair represents good value depends on the age and overall condition of the system and the nature of the fault. We give you an honest assessment at the diagnostic stage, including our view on whether repair or replacement is the better option for your specific situation.
Yes. Alongside our solar thermal repair service, we provide a dedicated solar thermal maintenance service that covers annual system inspections, fluid testing and replacement, pressure checks, pump and controller assessment and full system reporting. Regular maintenance is the most effective way to prevent unexpected faults and keep your system performing at its designed efficiency year after year. Ask us about our maintenance service when you contact us and we can discuss the options available for your system.
We carry out solar thermal repairs across Hampshire and a wide area of South England, including Surrey, West Sussex, East Sussex, Berkshire, Dorset, Wiltshire, Somerset, Devon, Kent, Oxfordshire, Gloucestershire, Buckinghamshire, Hertfordshire, Bedfordshire, Northamptonshire and Bristol. If you are unsure whether we cover your specific location, call us on 0330 111 9399 and we will confirm straight away.
Yes. Solar Maintenance And Repairs is NAPIT-registered and TrustMark-endorsed. Our engineers work to current UK industry standards on every job, including BS 7671 wiring regulations and the relevant solar thermal installation and servicing standards. We are also rated on Checkatrade and Trustpilot, where our customers consistently reflect on the quality of the work and service they have received. You can be confident that when we work on your solar thermal system, it is in qualified, experienced hands.
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