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Glow-Worm Boiler F.22 Fault Code

The Glow-Worm fault code F.22 relates to low water pressure and here we have Q & A or require an engineer for an emergency boiler repair.


The Glow-Worm Boiler Fault Code F.22 Error Common Q & A

Just below, we have a list of common questions relating to the F.22 fault code on the Glow-Worm Boiler.

Glow-Worm boiler error code F.22
  • What does the F.22 fault code mean on my Glow-Worm Energy boiler?
  • Why does my boiler lock out, and will resetting it fix the problem?
  • Will I need a new boiler if the F.22 fault code is showing on the display panel?
  • What’s the most likely cause of the fault on my Glow-Worm boiler?
  • What pressure should my Glow-Worm boiler be at?
  • My boiler’s pressure is below 0.5 bar, is there a DIY fix?
  • What causes a boiler to have low pressure?
  • I’ve topped up my boiler’s pressure, now it’s too high, what can I do?
  • Will resetting my boiler, allow it to work again?
  • How can I prevent my boiler from showing the F22 fault code in the future?
  • Is there a DIY fix to increase the pressure of my Glow-Worm boiler?
  • Is there a DIY fix to repair leaks in my heating system?
  • I’ve topped up my boiler with too much pressure, what do I do now?
  • What causes leaks, and the F.22 fault code to be displayed?
  • How do leaks occur, and how can they be fixed?
  • My boiler is leaking water, what could be the cause of the leak?
  • Why would the heat exchanger leak on my Glow Worm boiler?
  • Where do air locks occur, and can they be removed?
  • Why would the pump on my Glow-Worm boiler be leaking?
  • What should I do if my pump is blocked full of heating sludge?
  • If my boiler is leaking, could it have caused damage to other components?
  • My boiler engineer thinks it’s the pressure release valve or expansion vessel causing the problem, could this be right?

What does the F.22 fault code mean on my Glow-Worm Energy boiler

If your Glow-Worm Energy boiler is showing the F.22 fault code on the display panel, it means that your heating system has low water pressure.

For water to circulate correctly, a constant pressure needs to be maintained. When this pressure reduces, you’ll see the fault code displayed, and sometimes, the boiler will lock out until the problem is fixed.

Why does my boiler lock out, and will resetting it fix the problem?

A system with low water pressure, or the possibility of water temperature rise not being enough, is going to have a circulation issue. And, that’s going to put excess strain on a range of expensive boiler components, including the heat exchanger and the pump. Continued operation would likely damage both components, adding to the existing cost of repair.

And, that’s why we never suggest resetting your boiler to try and clear a fault code. The boiler may work for 1-2 minutes, until the printed circuit board (PCB) determines that the fault still exists. During these few minutes, damage could be caused.

Instead of resetting your boiler, speak to a Gas Safe boiler repair company. Those with Gas Safe accreditation, are the only ones legally allowed to fix gas appliances. They’ll be able to diagnose and fix the problem, and then reset your boiler to clear the F22 fault code.

Will I need a new boiler if the F.22 fault code is showing on the display panel

It’s rare that the F.22 fault code is going to lead to you needing a new boiler. There are a range of DIY temporary fixes. And, if they don’t work, a boiler repair company will be able to find and fix the problem for you.

What pressure should my Glow-Worm boiler be at

Boilers work best at 1.3 bar (always check your owner’s manual). However, they will usually continue to operate between 0.5-3 bar. If they go above 3 bar, they will lock out. The high pressure could damage components, and cause leaks.

When boiler pressure is too low, many components will have to work overtime, wearing out more quickly than they should. A typical example is boiler’s pump.

Once your boiler drops below 0.5 bar, it’s likely to lock out.

What causes a boiler to have low pressure

There’s a small chance that the engineer forgot to top up the boiler’s pressure when they last worked on it. But, if the boiler worked fine prior to the fault, then suddenly locked out due to low pressure, there’s a chance that the cause is a leak.

It’s the amount of water in a system that creates pressure. So, as water is lost via leaks, pressure is lost too.

I’ve topped up my boiler’s pressure, now it’s too high, what can I do?

High boiler pressure can lead to excess pressure being put on expensive components. And, that’s going to mean in the long-term, expensive repair bills. So, you shouldn’t run your boiler at more than 1.3 bar.

If you’ve topped up your boiler to over 1.3 bar, there are two easy ways to remove water, and therefore, pressure.

First, you can locate the drain cock. You can connect a small hose to the drain cock and drain water outside. You’ll need to have someone to keep an eye on the boiler’s pressure, and let you know when it drops to 1.3 bar.

The second option, if you can’t find the drain cock, is to drain water from towel rails, or radiators. Each will have a small bleed valve. Using these bleed valves can be messy, so make sure you cover walls and floors, and have a container to catch water.

Open the valve, until water pressure on your boiler drops to 1.3 bar. As you do this, you may hear a hissing noise. Once this hissing noise stops, water will start to drain from the valve. The hissing noise is simply air escaping from your heating system. And, this is a good thing; air locks act like blockages and could be contributing to your system’s low pressure and inability to circulate water correctly.

Will resetting my boiler, allow it to work again

The lock out function in your boiler, is designed to protect internal components from damage. Simply resetting the boiler without fixing the problem at hand, is going to do nothing. As soon as the boiler attempts to fire up, the pressure sensor will send a signal to the printed circuit board (PCB), to say that pressure is too low. That’s going to lead to an immediate lock out.

If you’re uncertain of how to fix the problem, you’ll need to call a boiler repair engineer. They’ll reset your boiler, only once they feel the leak has been fixed.

Remember, leaks don’t just affect your boiler. Water leaking throughout your property could cause extensive water damage, so you’ll want to fix the problem as soon as possible.

Is there a DIY fix to increase the pressure of my Glow-Worm boiler

You can top up the boiler’s pressure, using the external filling loop. This is a small braided hose with a valve on it, usually located just below the boiler’s casing. By opening this valve, you’ll allow water into the system, and pressure to increase.

However, you should speak to an emergency heating engineer first. To fix the F.22 fault code on a long-term basis, the leak needs to be found and fixed. If it’s not, your system will continue to leak, and the boiler will lock out again soon.

Is there a DIY fix to repair leaks in my heating system

There are products available such as Fernox F4, which is a leak sealer for central heating systems. Realistically, they could fix the leak completely. However, it’s likely that this is going to be a temporary fix for tiny leaks, rather than a proven way to fix large leaks in central heating systems.

I’ve topped up my boiler with too much pressure, what do I do now

If you’ve opened the valve on the filling loop for too long, you’ll have allowed too much water into the boiler, and the boiler’s pressure will be too high. You’re aiming for 1.3 bar. If it’s any higher than this, you’ll need to release some water from the heating system.

If you can locate the drain cock, you can open this to allow water to be released. If you can’t find the drain cock, you can bleed radiators of water, and this will drop the boiler’s pressure.

Be aware, this can be messy. So, you’ll want to have containers to catch the water, and towels to protect the walls and flooring around the radiator. You’ll also need someone to help you. They can check the boiler’s pressure gauge as you release water from the radiators, telling you when the pressure gauge reaches 1.3 bar.

What causes leaks, and the F.22 fault code to be displayed

Unfortunately, leaks are not always easy to spot. They can come from any part of the heating system. So, the leak could be inside the boiler, on the back of a radiator, or even coming from weak copper pipework that’s located underneath the floorboards.

We regularly get called out to fix the F.22 fault code on Glow-Worm boilers, where the property owner thinks there isn’t a leak, just because it’s not in plain sight.

My boiler is leaking water, what could be the cause of the leak

If you’ve noticed water around your boiler, there’s a good chance that the culprit for the F.22 fault code being displayed is behind the boiler’s casing. Typically, there are two main culprits; the heat exchanger and the pump.

Why would the heat exchanger leak on my Glow Worm boiler

The heat exchanger is extremely fragile. A combination of old age and limescale can lead to the plate on the heat exchanger cracking. When it does, this is going to lead to a leak.

It’s unlikely that a boiler repair company is going to be able to fix the heat exchanger. However, they will be able to fit a new one. Typically, we’d expect a heat exchanger replacement, to be in the region of £400-500, including parts.

Where do air locks occur, and can they be removed

As we mentioned in the section about reducing water pressure, you can remove air locks from radiators and towel rails via the bleed valve. But, there’s another place that you can remove air from, and that’s the pump.

The pump has a bleed screw that will help remove air locks. However, accessing the pump means taking the boiler apart, and this should only be done by a qualified boiler repair company.

Why would the pump on my Glow-Worm boiler be leaking

The pump is another culprit when it comes to leaks. In the case of the pump, it’s likely that the seals have blown. This is allowing water to escape. Like the heat exchanger, this could simply be due to old age. However, it’s likely the boiler’s pressure has been too high, or there’s been a heating sludge blockage in the pump, causing it to strain.

If the rest of the pump is in good condition, the pump’s seals can be replaced. If not, expect the boiler repair company to suggest a replacement. Typically, we’d expect a replacement pump from a top brand like Grundfos, to cost around £250.

What should I do if my pump is blocked full of heating sludge?

If your boiler engineer suspects that heating sludge is the problem, they’ll want to do more than just clean it from the pump.

What they’ll need to do, is hot flush the central heating system using chemicals. Once done, they’ll refill the system, dosing it with central heating inhibitor. As sludge circulates, the inhibitor will break it down into small manageable chunks. And, by installing a magnetic boiler filter, all these small sludge particles will be caught, and removed from the system.

If my boiler is leaking, could it have caused damage to other components

With your boiler repair company already inspecting and fixing your boiler, it’s wise to ask them to do a full inspection. The problem with leaks, is that the fault is rarely limited to the leak itself. Water and electrical parts don’t mix, and your Glow-Worm boiler is full of electrical components.

So, you’ll want to check that the water hasn’t damaged other expensive components. Components worth asking your boiler engineer to check include the PCB, gas valve and ignition lead. If the water has made its way into these parts and damaged them, there’s a good chance that your boiler will fail completely in the future. In that sense, it would make sense to replace the boiler, rather than spending hundreds on repairs.

My boiler engineer thinks it’s the pressure release valve or expansion vessel causing the problem, could this be right

The first point of call is always to check for leaks; this is the most common cause of a boiler losing pressure. However, it is a possibility that it’s not a leak, and instead, a faulty component.

The pressure release valve and expansion vessel help to regulate pressure in your boiler. If they’re not working correctly, it can lead to boiler pressure being too high, or in this case, too low. If there’s no water leak in the heating system, it’s likely re-pressurising the expansion vessel, or replacing the pressure release valve, is going to fix the F.22 fault code.

Other Glow Worm boiler issues

For more boiler issues regarding the Glow Worm then please visit the Glow Worm Boiler Problems And Cures page.