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There’s nothing more frustrating than waking up to a cold home, particularly when your boiler beeps out that annoying “F75” code. The F75 fault is a common issue with Vaillant boilers, and yes – it’s a real pain. This fault typically indicates a broken pump, a suspect pressure sensor, or a leak in the heating system.
Don’t panic, however. This article will guide you through what exactly the F75 fault in a Vaillant Boiler indicates, how to identify the symptoms, and what you do next, be it’s a simple fix or time to hire a Gas-safe engineer.
What is the Vaillant Boiler F75 Fault Code?
The F75 fault code indicates that your Vaillant boiler is failing to respond to a pressure change when it tries to start the pump. In other words, it switches on the pump but does not “sense” the water flowing. When that happens, it shuts down as a safeguard mode.
This problem is typically caused by:
- A malfunctioning pump (not functioning as it should)
- A faulty pressure sensor (cannot sense the pressure of water correctly)
There may occasionally be a minor leak in the system, but more so with the F22 fault. You may try to reset the boiler by simply restarting it, and it may work temporarily. It’s always best to identify the actual cause and rectify it to avoid future issues.
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Causes of Vaillant Boiler Fault Codes F75
The Vaillant F75 fault has numerous possible causes. Let’s discuss the most common causes of the F75 fault code by Vaillant:
1. Defective Pressure Sensor
One of the most common reasons. The pressure sensor monitors the pressure of the water in your boiler. The sensor becomes clogged with dirt, limescale, or sludge (also called magnetite) over time.
Magnetite forms when corrosion begins to build up internally in your heating system — it is like dirty water with a dark mud colour that ruins the parts of your boiler.
Older models of Vaillant boilers (particularly before 2010) are more prone to sensor issues. In case the boiler is functioning normally but indicates F75 anyway, the problem typically lies in the pressure sensor.
2. Faulty Pump
The pump on your boiler distributes water through the system. The pressure will not change if the pump is not functioning, and you will receive the F75 code.
The pumps used on early Vaillant boilers used to be somewhat inferior and were susceptible to splitting or leaking, or simply failing.
In case your boiler is turned on but you’re unable to hear or sense the pump operating, it is likely that the pump is responsible for the cause of the Vaillant F75 fault pump water shortage.
3. Low Water Pressure
Boilers require proper water pressure to function. The system will not work properly if the pressure is too low (typically less than 1.0 bar).
The boiler will attempt to initiate start-up when it is too low, but the pressure sensor will not detect an adequate change, and that triggers the F75 error.
You may wish to check the pressure on the gauge on the boiler front. This must normally read between 1.0 and 1.5 bar when cold.
4. Leaks in the Heating System
Leaks will drain water slowly from your system. Enough water leaking out causes the pressure to drop. The sensor will fail to notice a difference when the pump operates, and the boiler will show an F75 fault code.
Leaks are relatively rare but do occur. You’ll first need to rule out issues with sensors and pumps. In case both are okay and you’re still experiencing the F75 fault, it makes sense to check for leaks, particularly around joints, radiators, and pipework.
5. Electric Faults
Loose or damaged cables connecting the pump and sensor also produce the F75 error. The two parts are unable to “communicate” with each other if the cables are loose or damaged. This will shut down your boiler.
6. Airlocks in the System
At times, air may get trapped in your radiators or heating pipes. This condition is referred to as an airlock. It prevents water from flowing as it should, and your boiler is unable to pick up on a pressure fluctuation. That’s when the F75 fault occurs.
You’ll be able to rectify this by bleeding the radiators. If you notice gurgling or some of the radiators are cold at the top, there’s likely air in the system.
How to Diagnose the Vaillant F75 Fault Code?
If you own a F75 Vaillant ecoTEC Pro 28 or an ecoTEC Plus model, the F75 fault code is probably something you’ll eventually experience at some point.
This fault usually means the boiler cannot detect a change in water pressure when it switches on the pump. Is it the pump or the pressure sensor? Let’s check.
Step 1: Is it the Pump?
The pump is used to circulate hot water around your heating system. Should it fail to work properly, the boiler will fail to read the pressure drop it needs to start up, and then the F75 error will show up.
Here is a simple test to check if the problem is with your boiler pump:
- Turn on the boiler and press the reset button on it (the little symbol that has a flame).
- Wait a couple of minutes while the boiler restarts.
- Turn on a hot tap close by and wait a moment.
Pay close attention—do you hear a gentle hum or feel a soft vibration coming from the boiler?
If so, your pump is working as it should. Otherwise, if you do not hear anything and do not feel any vibration, it means the pump has malfunctioned or jammed and needs to be repaired or replaced.
Step 2: Could it be the Pressure Sensor?
If the F75 Vaillant ecoTEC Pro 28 pump appears to be working but hot water is still shutting off intermittently, the pressure sensor is likely to be at fault.
Over time, the dirt and limescale, and a type of sludge called magnetite, accumulate and clog up the pressure sensor. The pressure sensor cannot calculate the water pressure if it is clogged. The boiler thinks it is faulty, and it also switches off.
How to Fix the F75 Error Code?
If your boiler is showing the F75 fault, it’s certainly a job that’s best left to the professionals. The F75 fault does have a range of causes, and it’s best to call a Gas Safe-registered engineer to sort it out properly.
1. Call a Qualified Professional
You’ll need a specialist who has experience with Vaillant boilers. One good choice is a person who’s part of the Vaillant Advance Installer Scheme because they’ve received proper training and experience with this brand.
Upon arriving on-site, the engineer will:
- Check the pressure sensor and the boiler pump
- Notify you precisely why the F75 fault code has been activated
- Recommend the best course of repair — maybe a new pump, or a Vaillant F75 pressure sensor replacement
2. What is a Gas Safe-Registered Engineer?
A Gas Safe engineer is a person who has been fully trained and officially certified to work on gas appliances in the UK. They work to strict standards set by the Health and Safety Executive.
All Gas Safe engineers have a genuine ID with a serial number — simply ask to see it to reassure you. They’re not a nice-to-have — it is the law.
3. Pressure Sensor Replacement: Is It Worth It?
If the fault had been caused by dirt or debris or magnetite accumulating on the sensor, it would appear to be a simple matter to clean and rectify the problem. But the thing is: cleaning could also prove to be as costly as replacing it with a brand-new sensor, considering labour costs.
That is why engineers usually advise opting for a full Vaillant F75 pressure sensor replacement. It is faster, more durable, and prevents more failures in the future.
4. Keep Your Boiler Healthy with Annual Servicing
Avoid bothersome faults like the F75 in the long term by having your boiler serviced annually. It’s the simplest route to detecting minor issues before they grow into costly setbacks. What’s more, it keeps the system functioning optimally all year long.
5. Time for an Upgrade?
If your boiler is outdated or you’re noticing the F75 error repeatedly, it may be time to consider a full system upgrade.
Though repairing a solitary component, such as the pump or sensor, temporarily does the job, a newer boiler will perform better and last longer.
And if you are eligible for the ECO4 scheme, you could receive a brand-new boiler with the help of the free boiler replacement grant.
Vaillant Boiler Fault Codes F75 Reset
When your Vaillant boiler displays the F75 error code, the first thing to do is a simple reset. It may not solve everything, but it is a fast means to test if the issue corrects itself, and it takes a matter of minutes.
Here’s how to reset it step-by-step:
1. Press the Reset Button
Locate the reset button on the front of your boiler – it’ll probably have a small icon of a flame on it. Hold it down for a couple of seconds. This instructs your boiler to restart and retry.
2. Give It a Moment
Allow the boiler to restart. This typically takes around 2-3 minutes.
3. Run a Hot Tap
Switch on a hot tap close by. This instructs the boiler to heat up and begin warming water.
Listen carefully — you’ll hear a gentle humming sound and possibly a soft vibration. That’s the pump at work.
4. What Comes Next?
If the pump operates and the F75 error goes away – wonderful! It probably was a minor glitch.
But if the pump does work, but the error persists, it typically means your pressure sensor is the issue.
If the pump does not turn on at all, the pump itself could be defective, or it may have a more serious problem, like low pressure or an airlock.
How to Prevent the Vaillant Boiler F75 Fault Code Error?
The easiest way to avoid the F75 Vaillant ecoTEC Pro 28 fault is to have your boiler serviced annually. It’s simple, inexpensive, and could save you money on larger repair costs in the long term.
This helps a Gas Safe engineer to identify any minor faults, such as initial damage or debris in the pressure sensor, before they become a more serious issue.
Why it matters:
- Regular annual service is usually necessary to maintain your Vaillant guarantee.
- The engineer will perform a simple cleanup, investigate leaks, and confirm key components such as the pump and pressure sensor are functioning properly.
- It keeps you away from unwelcome shocks and costly maintenance.
By staying on top of annual boiler maintenance and performing a power flush when necessary, you’re far less likely to experience the return of the Vaillant F75 fault code.
The Bottom Line
The Vaillant F75 fault code is typically associated with issues with the pressure sensor or pump on the boiler. You might resolve it temporarily with a reset, but long-term solutions require a Gas Safe engineer.
Maintenance and occasional power flush can do wonders to avoid the same problem in the future. Acting now to maintain your boiler means fewer headaches—and less expense—later on.
Frequently Asked Questions
The F75 fault indicates that your boiler cannot sense a change in water pressure when it’s starting up. The most common causes are a malfunctioning pump, a clogged pressure sensor, or sludge in the system.
Inspect the pressure gauge—if low, fill it up by using the filling loop. Otherwise, the pump or pressure sensor might require cleaning or renewal. Contact a Gas Safe engineer.
Yes. F75 faults include internal components that may be hazardous to work on. A Gas Safe engineer is lawfully qualified to repair them safely and properly.
