Boiler guidance

Heating water and your boiler warranty

Your boiler warranty may include conditions about installation, servicing and heating water. The wording varies by manufacturer and model, so start with your own documents before deciding what your system needs.

What to check

Your own documents

Read the current warranty or guarantee terms for the exact boiler model and keep installation, commissioning and service records.

Manufacturer instructions

Follow the appliance and water-treatment guidance supplied by the manufacturer rather than relying on a general website summary.

Recorded evidence

Water checks and before-and-after records may help document condition, but they do not determine whether a particular claim will be accepted.

What a water check can and cannot tell you

Poor water quality may affect support where it contributes to damage or conflicts with applicable terms, but it does not automatically invalidate every boiler warranty. Only the relevant manufacturer or warranty provider can decide an individual claim.

Do not add chemicals or commission cleaning solely because of a general article. Check the system, product instructions and competent professional advice first.

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What evidence may manufacturers ask for during a boiler warranty claim?

Boiler manufacturers may ask for evidence that the heating system has been installed, serviced and maintained in line with their requirements.
This may include service records, benchmark documentation, water treatment information and evidence that the heating system water has been cleaned, treated and maintained appropriately.

Can poor heating system water quality affect a boiler warranty?

Poor heating system water quality may affect warranty support if it contributes to component damage or if the system has not been maintained in line with manufacturer guidance.
Manufacturers commonly expect heating systems to be cleaned, treated and protected appropriately, especially when a new boiler is installed.
Testing can help provide evidence of water quality, inhibitor protection and water balance over time.

How can testing help after a professional heating system clean?

Testing before and after cleaning can help show how the condition of the system water has changed.
A first test can help identify the starting condition. A follow-up test after cleaning can help show whether water quality, inhibitor protection and water balance have improved.
This provides useful before-and-after evidence rather than relying on guesswork alone.

Will adding my own chemicals affect my boiler warranty?

Using the wrong chemical, adding too much, adding too little or treating the system without understanding the water condition may affect system performance and could create warranty concerns.
It is important to follow manufacturer guidance and use appropriate water treatment products correctly.
Testing first can help you understand whether inhibitor, cleaning or further investigation may be relevant before adding chemicals.

Should radiators be flushed when replacing a boiler?

When replacing a boiler, the existing heating system should be assessed, cleaned and treated in line with the boiler manufacturer’s requirements and recognised industry guidance.
Old radiators and pipework can contain sludge, debris or poor-quality system water. If this is not addressed, it may affect the new boiler and reduce long-term system protection.
Testing can help create a clearer record of system condition before and after work is completed.