Vaillant F75 Fault Code: Causes & How To Fix

Vaillant F75 fault code – What it is & how to fix it

The Vaillant F75 error code is a frequent issue for UK homeowners, landlords, and commercial property managers using Vaillant boilers, especially older models like the ecoTEC Plus and ecoTEC Pro.

This fault indicates the boiler cannot detect a pressure change when the pump activates, often resulting in no hot water or central heating. If you’re facing this error, you’re likely considering whether to repair or replace your boiler.

This in-depth guide offers expert insights into the Vaillant F75 fault code, its causes, solutions, and guidance on whether a boiler replacement suits your property. We’ll also explore preventative maintenance to help you avoid costly repairs and maintain efficient heating for your home or commercial building.

What Is the Vaillant F75 Error Code?

The Vaillant F75 error code signals that the boiler’s control unit has detected no pressure change when the pump starts. According to Vaillant’s documentation, this fault occurs when the pressure sensor or boiler pump fails to register a pressure rise, resulting in the boiler locking out as a safety measure.

This disrupts the supply of hot water and central heating, leaving properties without essential heating services.

This error is most prevalent in Vaillant EcoTEC models manufactured between 2005 and 2010, which used less reliable Wilo pumps and pressure sensors prone to failure. While newer models incorporate more robust Grundfos pumps, the F75 fault can still occur due to debris buildup or system issues.

Calling a qualified engineer to look at the boiler for you will likely be the best course of action, as looking at it yourself could potentially be dangerous or further break the boiler. A Gas-Safe engineer will have the knowledge and experience in this situation to properly repair your boiler for a reasonable price.

Boiler cover may be able to help with the costs of part replacements and the repairs that your Vaillant boiler needs.

Common Causes of the Vaillant F75 Error Code

Understanding the cause of the F75 fault is essential for deciding between repair and replacement. The primary reasons include a faulty pressure sensor, defective boiler pump, low system pressure, or airlocks and blockages.

A clogged or defective water pressure sensor, which monitors pressure changes in the hydronic loop, often becomes obstructed by debris, limescale, or magnetite (corrosive sludge). This prevents pressure detection, triggering the F75 error, especially in older EcoTEC models. Cleaning the sensor is rarely cost-effective, and replacement, costing £50–£100, is often advised.

A defective boiler pump, responsible for circulating water, can also fail to generate sufficient pressure, particularly in pre-2005 models with Wilo pumps prone to leaks. Pump replacement costs £250–£350, but for boilers over 10 years old, a new unit may be more economical.

Low system pressure from leaks in pipework, radiators, or components like the automatic air vent (AAV) or pressure relief valve (PRV) can also prevent pressure rises. Leaks, though less common, require a Gas Safe engineer to inspect and repair. Finally, airlocks or blockages from debris can disrupt water flow, especially in unserviced systems, and may require a power flush costing £300–£500.

How to Diagnose the Vaillant F75 Error Code

Diagnosing the F75 fault involves systematically checking the pressure sensor, pump, and system pressure. Start by confirming the F75 error code on the boiler display, noting any alarms or flashing lights.

Reset the boiler by pressing the reset button (often a flame icon) and run a hot tap to trigger it. Listen for the pump’s hum and feel for vibrations. A silent pump suggests a faulty unit, while an operating pump with no hot water points to a sensor issue.

Check the pressure gauge to ensure the system pressure is between 1–1.5 bars; repressurise if below 1 bar per the boiler manual. Inspect for leaks by looking for damp spots or corrosion around the boiler, radiators, or pipework. For accurate diagnosis, contact a Gas Safe registered engineer, as DIY fixes can void warranties and pose risks.

Regular Vaillant boiler servicing can prevent issues like debris buildup or pump wear, and it’s often a warranty requirement for Vaillant boilers.

How to Fix the Vaillant F75 Error Code

Fixing the F75 fault typically requires professional expertise due to the complexity of boiler components.

If the pressure sensor is clogged or defective, a Gas Safe engineer can replace it for £100–£200, a quick fix for newer boilers but less economical for older models. A faulty pump requires replacement, costing £250–£350, but for boilers over 10 years old, a new unit may be wiser.

Leaks causing low pressure need repairs to components like the AAV or PRV, with costs ranging from £150–£300. A power flush, priced at £300–£500, removes magnetite and debris to restore efficiency and prevent future errors. Homeowners can bleed radiators to address airlocks, but persistent issues warrant professional attention.

For boilers over 15 years old, repair costs may rival the price of a new, energy-efficient model, which can save up to 30% on energy bills and include a 10-year warranty.

Other common Vaillant fault codes

• Vaillant F22 fault code
• Vaillant F28 fault code
• Vaillant F29 fault code
• Vaillant F32 fault code

Should You Repair or Replace Your Vaillant Boiler?

Deciding whether to repair or replace a boiler with the F75 error hinges on the boiler’s age, repair costs, and your property’s heating needs.

Repair is suitable for boilers under 10 years old, in good condition, with repair costs below £300, and when the boiler meets your heating demands. For example, a 5-year-old Vaillant EcoTEC Pro with a faulty sensor can be economically repaired, extending its life.

Replacement is better for boilers over 10–15 years, especially pre-2005 models with Wilo pumps, those with frequent faults (e.g., F75, F28, F22), or when repair costs exceed £500. If the boiler struggles to heat larger homes or commercial properties, a modern, A-rated combi boiler offers better efficiency.

Vaillant boiler Maintenance

Preventing the Vaillant F75 Error Code

Preventative maintenance is key to avoiding the F75 fault and prolonging your boiler’s life.

Annual boiler servicing by a Gas Safe engineer, costing £80–£150, ensures the pump, pressure sensor, and components are checked and cleaned, meeting Vaillant warranty requirements. A power flush every 5–7 years removes magnetite and limescale, while monthly pressure checks keep the system between 1–1.5 bars.

Bleeding radiators annually prevents airlocks, and installing a magnetic filter (£100–£200) traps magnetite before it clogs the sensor. Adding a chemical inhibitor during servicing reduces corrosion.

For landlords, regular maintenance ensures compliance with Gas Safety Regulations 1998, keeping tenants comfortable and reducing emergency callouts. A boiler cover plan can simplify servicing and repairs. Commercial buildings with higher heating demands benefit from system boilers and frequent power flushing to maintain efficiency.

Getting your Vaillant boiler serviced annually is the best way to stay on top of issues such as the F75 fault code and other common fault codes. This will mean an engineer can regularly examine and monitor your boiler and then inform you if there is anything that is in need of repair.

Fixed prices for Vaillant boilers

If you keep having problems with your Vaillant boiler, then this may be a sign to get a boiler replacement, which could spare you from a lot of the issues you were facing. It could also be much more financially rewarding for you, as you won’t be paying tons of money for repair costs all the time.

Check out our selection of Vaillant boilers to find the ideal one for your home.