A How to Guide on How to Repressurise a Ferroli Boiler

If you just discovered that your home’s Ferroli boiler has turned itself off, the pressure could drop below its optimal range.

It’s not unusual for any modern boiler to lose pressure from daily use, and it is easy to fix yourself.

Like other modern boilers, Ferroli units will shut down as a safety measure when the pressure falls too low. Also, you will know that your Ferroli boiler must be repressurised if it displays the error code F37, which clearly states that there is insufficient system pressure.

Usually, most boilers in the UK must be repressurised once a year or none if you have an annual boiler service scheduled.

However, if your Ferroli boiler needs to be topped up more frequently, there are several common reasons why it might need to be repressurised.

What Causes A Ferroli Boiler To Lose Pressure?

While your boiler may lose some pressure if it drops too low frequently, there are several common reasons why this can happen.

These reasons include the following:

1. Small Leaks In The System

Most boiler pressure issues stem from small leaks in the heating system, which are often so subtle that you don’t even notice them. Tiny drips from pipes, radiators, or internal components can add up over time.

Common signs that there’s a small leak include:

• Water puddles under radiators or pipe joints.
• Damp patches on walls, ceilings, or floors.
• A gradual drop in pressure readings over days or weeks.

Even tiny leaks can cause significant pressure loss.

For example, a pressure drop from 1.5 to 0.5 bars indicates the loss of approximately three litres of water. The system would only need to leak at 17ml per hour to lose three litres a week, slightly more than a tablespoon (15ml).

If you suspect a leak, it’s time to call in a Gas Safe registered engineer to find and fix the problem.

2. Trapped Air In The Radiators

Air pockets are another common culprit. If your radiators have cold spots at the top but are warm at the bottom, this is a sign that trapped air in the radiator prevents hot water from circulating properly.

Bleeding your radiators can solve this, but allowing too much water to escape can lower the system pressure to a low level, triggering the safety shut-off.

Pro Tip: Always check the pressure gauge after bleeding your radiators. If it’s too low, you must top it up using the filling loop (more on that below).

3. Faulty Pressure Relief Valve (PRV)

The PRV is your boiler’s safety net, releasing excess pressure to protect the system.

If the valve is faulty, it might leak water unnecessarily, causing a pressure drop.

Call a professional if you notice water dripping from the PRV outlet or steadily venting out pressure. Only a Gas Safe-registered engineer can check and replace the valve if necessary.

4. Expansion Vessel Problems

The expansion vessel is a small tank inside your boiler that absorbs pressure changes as the water heats and expands.

The system can\’t regulate pressure properly if the vessel loses its air charge or its internal diaphragm fails.

A faulty expansion vessel often leads to:

• Sudden pressure drops.
• Frequent system shutdowns.

A Gas Safe registered engineer will need to repair or replace your boiler’s expansion vessel.

5. Condensate Pipe Freezing

If the outside temperatures dip below freezing for an extended period, your boiler’s external condensate pipe can freeze.

This blockage can cause pressure loss and error codes, such as F28 (an interrupted gas supply) or F37, on Ferroli boilers.

A few indications that your boiler’s condensate pipes are frozen include:

• Gurgling noises from the boiler.
• No heating or hot water.
• Water dripping or ice build-up on the pipe outside.

A simple way to fix this is to pour warm (not boiling) water over the pipe or wrap it with a warm towel until the ice melts.

Now, what is the best pressure for your Ferroli boiler to operate at?

What’s The Ideal Pressure For A Ferroli Boiler?

Ferroli boilers, like most modern systems, work best at a pressure range of 1 to 1.5 bars.

You can check this on the pressure gauge on the front of your boiler. Make sure that it aligns with the following criteria:

• If the needle is in the green zone, you’re good.
• If it’s too low (below 1 bar), it’s time to repressurise.
• If it’s too high (above 2 bars), you must release some water by bleeding your radiators.

However, always check your boiler’s manual, as pressure levels can differ.

Now, if you’re confident your Ferroli boiler needs to be repressurised, here’s how!

How To Repressurise A Ferroli Boiler

Repressurising your Ferroli boiler is a straightforward job. Follow these steps carefully:

Step 1: Turn Off The Boiler

Switch off the boiler and let it cool for an hour or two.

Working on a hot system can be dangerous and give inaccurate results when reviewing pressure levels.

Step 2: Locate The Filling Loop

The filling loop is a pipe that connects your boiler to your home’s water mains and is used to top up its pressure.

It’s usually found underneath the boiler filling loops and can either be:

• An external filling loop: A flexible braided hose that connects your boiler to the mains water.
• An internal filling loop: Built into the boiler with a key-operated system or lever taps.

While different, they both perform the same job.

Step 3: Gradually Open The Valves

For both filling loops, you need to open them up in a sequence, which is as follows:

• Open the first valve to allow mains water into the system.
• Slowly open the second valve while keeping an eye on the pressure gauge.

The pressure will start to rise. Stop when the gauge reads 1 to 1.5 bars, and don’t overdo it, as you risk overpressurising.

If you’re unsure if the valve is open, the tap will be perpendicular to the pipeline when it is open and in line when closed.

When closing the valves, turn off both valves in the reverse order.

If you’re using an external loop, detach it and store it safely (a little water might drip, so have a towel handy).

Step 4: Switch The Boiler Back On

After a few minutes, turn the boiler back on and check the pressure gauge. You’re all set if the pressure stays steady in the green zone.

But what should you do if the pressure keeps dropping?

What If The Pressure Keeps Dropping?

If your boiler loses pressure after repressurising, there’s probably an underlying issue.

And no matter what the issue is, whether it is:

• A leak,
• Faulty PRV,
• Or an expansion vessel problem.

At this point, it’s best to call a professional.

Need A Hand? WarmZilla Has You Covered

If the pressure problem keeps recurring, call in a WarmZilla Gas Safe registered engineer who can quickly and safely resolve the issue.

Whether you have a leak, a faulty component, or a frozen pipe, we’ve got you covered, as WarmZilla offers emergency repairs within 48 hours across the UK.