Potterton Boiler E118 Fault Code


The Potterton fault code E118 low boiler pressure Q & A or require an engineer for an emergency boiler repair.


The Potterton Boiler Fault Code E118 Error Common Q & A


Just below, we have a list of common questions relating to the E118 fault code on the Potterton boiler.

Potterton Boiler E118 Fault Code

  • What does the E118 fault code mean on my Potterton boiler?
  • What causes the E118 fault code to be displayed on my Potterton boiler?
  • Why does my boiler lock out if there is a small leak in the heating system?
  • Is it dangerous to reset a boiler showing the E118 fault code?
  • Where will a boiler engineer start, to try and find and fix the leak?
  • Can I just top up my boiler’s pressure to fix the leak?
  • What would cause the heat exchanger to leak?
  • Can a heat exchanger be replaced to clear the E118 fault code?
  • Why does a boiler pump leak?
  • What pressure would my boiler need to be to blow the pump’s seals?
  • Will the pump need to be replaced if the seals have failed?
  • How will my boiler engineer know if the boiler connections are loose?
  • How will I find leaks if they’re not in the boiler?
  • There is no visible leak, what is the problem?
  • My boiler engineer has suggested it could be the PRV or auto air vent, is this correct?
  • Is there anything else that can contribute to the E118 fault code being displayed?

What does the E118 fault code mean on my Potterton boiler


When your Potterton boiler develops a problem, it will usually stop working, and display a fault code. In this instance, the E118 being displayed relates to low boiler pressure.

Your boiler and central heating system needs a certain level of water (and therefore, pressure) in the system, to be able to work correctly. Generally, a boiler will lockout then pressure is anything below 0.5 bar, and above 2 bar.

What causes the E118 fault code to be displayed on my Potterton boiler


The most probable cause of the fault code being displayed, is a leak. Your boiler shouldn’t lose pressure. If it does, water is being lost from somewhere in the system. Any leak, regardless of how small, will contribute to a loss in boiler pressure.

Why does my boiler lock out if there is a small leak in the heating system


Boiler lock outs, alongside a fault code being displayed, are an indication of the problem at hand. In this case, if the boiler continues to run, it’s going to force water from the heating system, through the area that’s leaking. This is going to cause property damage.

Alongside this, once the pressure of a boiler gets particularly low, it can then start to damage parts such as the pump and the heat exchanger.

Is it dangerous to reset a boiler showing the E118 fault code


The reason boilers have a lock out function incorporated is in this case, to protect your property and your boiler from more expensive repairs. So, the problem needs to be fixed before the reset function on your boiler is used.

You’ll need to call an emergency boiler engineer. They’ll be able to figure out where the leak is coming from and fix it. Once the leak has been fixed, only then should the boiler be reset.

Where will a boiler engineer start, to try and find and fix the leak


The first thing to do, is to isolate the leak to either the boiler, or the heating system.

Parts that leak in boilers include the:

  • Heat exchanger
  • Pump
  • Loose boiler connections

In the central heating system, it’s common for the following parts to leak:

  • Soldered joints on pipework
  • Radiator valves
  • Radiators

And, there are other things to consider, such as the low-pressure water sensor fault.

Can I just top up my boiler’s pressure to fix the leak


In theory, using the external filling loop to top up pressure (and therefore, water) in the central heating system will clear the E118 fault code. The problem is, this doesn’t fix the leak.

If the leak is present inside your boiler, the increased pressure is going to mean the leak is fast-tracked. And, that could mean water damage to expensive boiler components.

Likewise, if the leak is in a pin-hole in the back of radiators for instance, then that’s going to lead to damage to plaster, paint and wallpaper.

So, it’s advisable to fix the leak before topping up boiler pressure.

What would cause the heat exchanger to leak


Heat exchangers are robust boiler components. For them to leak before other parts in a boiler break, means there has been a catalyst. A typical cause of a leaking heat exchanger is a build-up of limescale.

When limescale builds up on the heat exchanger, it can lead to cracks. And, even tiny cracks can cause leaks that are big enough to cause a drop-in boiler pressure.

Can a heat exchanger be replaced to clear the E118 fault code


The heat exchanger can be replaced. But, it can cost upwards of £400. So, if you’re going to spend this kind of cash on replacing parts on your boiler, you’ll want to check all other parts are in good condition. That’s especially important, as the leak could have caused excessive damage to electrical parts in the boiler.

Why does a boiler pump leak


Old age can cause the boiler pump’s seals to wear out, and eventually blow. However, another probable cause is that the pressure was set too high on the boiler. This creates additional strain that the pump’s seals aren’t designed to cope with.

What pressure would my boiler need to be to blow the pump’s seals


There’s no exact answer here. A pump’s seals will weaken with age and that’s going to mean they fail much easier.

What’s more important is that your boiler is set to the correct pressure. Typically, modern Potterton boilers should be set at around 1.3 bar. They’ll tend to operate fine between 1 bar and 2 bar. Anything above 1.5 bar though, is not helping the boiler work to its optimum. And instead, it’s simply putting excess strain on parts, just like the boiler’s pump.

Will the pump need to be replaced if the seals have failed


Asides from the seals, if the pump is in good condition, it can be salvaged. Quality pump manufacturers of pumps offer spares kits. They’ll include all the essentials to recondition the pump, including the seals.

However, if the pump is showing excessive wear and is particularly old, it might be worth considering a replacement. Typically, you’ll expect to pay somewhere in the region of £250 for a replacement pump on a Potterton boiler.

How will my boiler engineer know if the boiler connections are loose


It’s a rare occurrence, but not unheard of; boiler connections can work themselves loose if they’re not secured correctly, or the boiler is vibrating excessively.

If connections are not secured correctly, this is going to become obvious with a quick visual inspection. The connections will be weeping with water, and there’s a good chance there will be pooling of water below the boiler.

This repair is a cheap one. The boiler engineer simply needs to tighten the connections, dry the offending area, and then check again for leaks. Once they’ve done this, they’ll be able to clear the E118 fault code by resetting your boiler.

How will I find leaks if they’re not in the boiler


Visually checking all visible parts of the heating system is going to help determine if there are leaks. Some leaks are so small, they’re hardly visible. For instance, a soldered copper joint that has worked its way loose could be dripping straight onto a carpet, and due to it’s colour, a damp patch could be hard to spot.

That’s why most plumbers prefer to use blue roll to dab areas that are likely to be leaking. This shows up after dabbing, even the smallest leak. When checking the heating system, you’ll need to make sure you feel the backs and underneath of radiators, pipework, radiator valves and towel rails.

There is no visible leak, what is the problem


The first thing to rule out, is whether the leak is in the central heating system, but just not visible. Lots of pipework is contained in walls, ceilings and floors. A tiny leak there is going to create a damp patch so small, it might take months to come through the plaster.

If there truly isn’t a leak, the boiler engineer will need to check the sensors in the boiler. The first point of call is to check the low-pressure water sensor. This is the unit that feeds back information to the printed circuit board (PCB). Once the PCB gets the signal that the boiler’s pressure has dropped below 0.5 bar, it will lock out the boiler. So, if the sensor is faulty, it might be giving the PCB the wrong reading.

One straightforward way to check this, is to determine your boiler’s pressure using the pressure gauge. If the pressure is above 0.5 bar but the boiler is still locking out, it’s likely that the low-pressure water sensor is to blame here.

My boiler engineer has suggested it could be the PRV or auto air vent, is this correct


Both devices help the boiler to relieve pressure. So, if the boiler’s pressure is suddenly too high (they’re not doing they’re job, at all), or too low (they’re potentially letting pressure escape when they shouldn’t), they are the culprits.

Your boiler engineer will be able to check the operation of the pressure release valve and the auto air vent. If they’re at fault, they’ll be able to replace them, reset your boiler and clear the E118 fault code.

Is there anything else that can contribute to the E118 fault code being displayed


If there are no leaks in the heating system or boiler and the PRV/auto air vent isn’t showing any faults; the PCB needs to be ruled out as the culprit. The PCB controls all electronic components in a boiler and receives signals from many of them.

It stands to reason that if there’s a fault with the PCB, it could be receiving the wrong signals from the low water pressure sensor and locking out the boiler prematurely.

Other Potterton boiler issues


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