Fact or Fiction: Are Buffer Tanks Really Necessary to Protect Your Heat Pump Warranty?

For UK homeowners investing in heat pumps, warranties have become an essential talking point. With many manufacturers tying extended warranties to specific installation requirements (such as the addition of a buffer tank) fundamental questions are beginning to surface: are these stipulations legally enforceable under the Consumer Rights Act 2015, and can a manufacturer lawfully deny a warranty claim based on such conditions?

Understanding the Consumer Protection Framework

The Consumer Rights Act 2015 (CRA) offers a strong and important framework for protecting UK consumers. It stipulates that any goods sold must be fit for purpose, of satisfactory quality and last a reasonable length of time. Importantly, consumers have up to six years to bring a claim against the seller in England, Wales and Northern Ireland, or five years in Scotland. Within the first six months after purchase, the burden of proof lies with the seller to show that the goods were not faulty at the time of sale – an important protection for homeowners investing in expensive systems like heat pumps.

However, when it comes to heat pumps, the legal landscape becomes far less straightforward. In practice, many homeowners do not pursue warranty claims against the original installer or retailer, but instead rely on extended manufacturer warranties – often stretching from five to seven years or more. These warranties are usually indirect agreements between the homeowner and the manufacturer, and as such, they fall outside the scope of basic consumer protections attached to the original sale. This creates a legal grey area where manufacturers set their own terms and conditions, often without much regulatory oversight.

One area of growing contention is the introduction of mandatory installation components (such as buffer tanks, volumisers or other ancillary equipment) as a condition of warranty validity. Some homeowners have related to us that some manufacturers specify that, in order for their warranty to remain active, a heat pump must be installed with a buffer tank, even where industry guidance (such as MCS standards) or Building Regulations do not explicitly require one. This raises key legal questions: Are such requirements enforceable? Are they fair? And could they be challenged under UK law?

Under the Consumer Rights Act, contract terms must be fair, particularly when dealing with consumers rather than businesses. An unfair term (such as an unreasonable technical condition buried in warranty small print) could potentially be challenged. The Competition and Markets Authority (CMA) provides guidance stating that warranty terms which attempt to unfairly limit a consumer’s statutory rights may not be legally binding.

If a manufacturer were to reject a valid warranty claim purely because a buffer tank was omitted (especially if the system was otherwise installed to industry standards and was fully operational) it could be argued that the refusal is disproportionate and potentially unenforceable. Much would depend on whether the manufacturer could demonstrate that the missing buffer tank directly contributed to the fault or premature failure. Without a clear causal link, the consumer could argue that the heat pump was not unfit for purpose simply because a non-mandatory component was missing.

In short, while manufacturers are entitled to specify conditions for extended warranties, they must act reasonably and cannot impose hidden or disproportionate obligations that conflict with broader consumer protection laws. The mere absence of a buffer tank would not automatically invalidate a consumer’s rights if the heat pump itself can still be shown to be defective, unfit for purpose or of unsatisfactory quality.

The Buffer Tank Debate

Manufacturers such as Samsung and LG, according to homeowners who have posted on the Renewable Heating Hub forums, require a buffer tank to be installed to maintain eligibility for their extended warranties, often justified on the grounds of preventing short cycling and reducing compressor stress. To verify this we reached out to Samsung and LG for comment, but they didn’t reply.

Nevertheless, Building Regulations do not mandate buffer tanks in all installations. Their inclusion is a matter of system design, influenced by the configuration of the property and the type of heat pump in use. MCS standards also do not categorically require buffer tanks for certification purposes. If an MCS-accredited installer deems a buffer unnecessary for a specific property, it raises the critical issue: can a manufacturer override that professional judgement and deny warranty coverage simply because a buffer was omitted?

Consumer law suggests that manufacturers cannot impose unfair terms that undermine statutory rights. If a product develops a fault due to a manufacturing defect, the absence of a buffer tank (if irrelevant to the cause of failure) should not absolve the manufacturer from responsibility.

Homeowners Caught in the Crossfire

Several Renewable Heating Hub members have already found themselves navigating the complexities of warranty disputes, often with unsatisfactory outcomes.

John, who installed a heat pump from Grant, remains uncertain about the extent of his warranty protection. “I’m still trying to verify this,” he said, “but I believe I need to work with a Grant-approved engineer in order to maintain my seven-year warranty, which may limit my options significantly in the long-term.”

Others have faced more direct challenges. Rick, a homeowner with a Samsung heat pump supplied via Joule, encountered a compressor failure during a severe cold spell. When he attempted to make a warranty claim, an engineer was dispatched – not to repair the fault, but, according to Rick, to search for grounds to void the claim. A previous electrical connection repair, unrelated to the current issue, was cited as “tampering,” leaving Rick battling a denial.

Mike’s experience further illustrates the inconsistency. His 12kW Samsung air source heat pump was installed with a buffer tank, yet the positioning of the tank complicated routine servicing. When he queried the necessity of the buffer, given that Samsung’s own documentation showed alternative system designs, he received conflicting responses, undermining his confidence in the warranty’s enforceability.

Another homeowner, Emceed, faced a different kind of obstacle. After Samsung repaired his failed compressor, he was later informed that his warranty had been voided retrospectively due to “insufficient flow rates” in his original system design. Samsung demanded the addition of a 50-litre buffer tank, yet other known installation defects remained unaddressed.

Across these cases, a pattern emerges: homeowners often find themselves caught between manufacturers, suppliers and installers, each pointing the finger elsewhere, while the burden of proof (and the financial risk) falls squarely on the consumer.

The Question of Annual Servicing

Annual servicing by an “approved” engineer is another common warranty condition, but it too raises legal concerns. While regular maintenance undoubtedly supports a system’s efficiency and lifespan, questions arise over whether manufacturers can lawfully void warranties due to missed services or the use of non-approved contractors.

Under the Consumer Rights Act, warranty terms must be proportionate and fair. If a fault stems from a manufacturing defect rather than neglect, the manufacturer’s obligation to repair or replace remains intact, irrespective of the servicing record. Efforts to restrict servicing to a closed group of approved engineers could also raise competition concerns under consumer protection regulations.

What the Law Says About Enforceability

Legal experts generally agree that manufacturers cannot impose warranty terms that are unfair or unreasonable. If a product fails due to a defect that would have manifested regardless of ancillary installation choices, such as the presence or absence of a buffer tank, the manufacturer is unlikely to be absolved of liability.

Furthermore, if the installation was conducted by an accredited, competent professional (and complied with relevant standards at the time) then attempts to deny a claim on technicalities unrelated to the cause of failure may be challengeable.

The burden should rest with the manufacturer to prove that an installation defect directly caused the problem at hand. In practice, however, homeowners often face an uphill battle navigating complex claims processes and technical arguments deployed to deny responsibility.

What the Manufacturers Say

NIBE is firm on their stance: while small systems with high flow may just about cope without a buffer, in the vast majority of UK installations (especially with underfloor heating or mixed radiator systems) they strongly recommend including one. They argue it stabilises flow rates, ensures smoother defrost cycles and protects the compressor from damaging short-cycling, which is critical for long-term reliability.

Daikin offers a nuanced view, distinguishing between a “buffer tank” and a volumiser. According to Daikin: “Our monoblocs will not require any additional volumiser if combined with our pre-plumbed cylinder range, as the cylinder provides the necessary hot water for defrost. If using a standard cylinder with a third-party shunt pump, a volumiser is also not needed. However, if combined with an optional back-up heater, a 10-litre volumiser is required. Without specific cylinders or pumps, 20 litres of additional volume must be present — either in pipework or via a volumiser.”

In short, Daikin’s system design flexibility makes buffers sometimes optional, but only when their own specific components or calculated pipework volumes are used. Otherwise, installers are expected to ensure enough volume is present to support stable operation.

Panasonic takes a slightly different line: “Do you require a buffer tank for full warranty coverage? No. It is up to the installer based on their design and calculations. It is an option if they want to fit one or not.”

However, Panasonic also clarifies that warranty coverage tiers depend on installation standards: to achieve a 5-year warranty, the installer must have attended Panasonic training, and for the full 7-year warranty, their Smart Cloud system must be fitted.

In practice, Panasonic leaves it to installer discretion, but this makes good design and thorough system commissioning critical to avoid post-installation performance issues.

What Should Homeowners Do?

For homeowners facing warranty disputes, several steps can help level the playing field. Keeping detailed records of the installation, including photographs and commissioning certificates, is vital. Retaining copies of all maintenance invoices, service reports and correspondence with manufacturers can provide crucial evidence if a dispute escalates.

If a warranty claim is refused, consumers should seek advice from organisations such as Citizens Advice or Trading Standards. Membership bodies like the Renewable Energy Consumer Code (RECC) and the Home Insulation and Energy Systems Contractors Scheme (HIES) may also offer arbitration and support services.

Ultimately, if a dispute cannot be resolved amicably, small claims court remains an option, and recent case law suggests that consumers have a reasonable chance of success if they can show that denial of a warranty claim was based on unfair or irrelevant conditions.

Every manufacturer agrees on one thing: proper system design matters far more than simply copying lab-tested numbers.

Buffer tanks (or volumisers) might not always be mandatory, but they often make a huge difference to system stability, defrost performance, compressor protection and overall longevity, especially in real-world UK winter conditions.

If you’re installing a heat pump, challenge your installer to explain their decision clearly.

And if you’re an installer, don’t cut corners: build in volume where it’s needed, and think beyond the bare minimum requirements.