Baxi Boiler 117 error code: Causes & Fixes

The 117 error code appears when your Baxi boiler detects that the water pressure in the heating system is too high. This safety feature stops the boiler from operating to avoid damage to pipes, valves, and other components. It is the opposite of low pressure faults and often happens after overfilling or due to other system issues.

What Does the Baxi Boiler 117 Error Code Mean?

The baxi boiler 117 error code means the system pressure has risen above the safe limit, usually over 2.5 to 3 bar. The boiler locks out to protect itself from the risks that come with excessive pressure. You will lose heating and hot water until the pressure is brought back down to the normal range.

What Causes the 117 Error Code on Your Baxi Boiler?

The 117 error code on your Baxi boiler is mainly caused by high system pressure from overfilling, a faulty filling loop, or problems with the expansion vessel. These issues can occur after topping up the system or during temperature changes. Getting to the root cause helps you fix it safely and prevent it happening again.

Overfilled System Pressure

This is the most frequent cause. It often happens when someone adds too much water using the filling loop or leaves the valves slightly open, pushing the pressure too high.

How to Fix

1. Turn off the boiler at the mains and let everything cool down.
2. Check the pressure gauge to confirm it reads above 2 bar.
3. Bleed water from a radiator using a radiator key, collecting the water in a container until the gauge drops to around 1 to 1.5 bar.
4. Close everything tightly, reset the boiler, and monitor the pressure over the next day.

Faulty Filling Loop or Valve

The filling loop used to add water can leak or stay partially open, allowing extra water into the system and raising the pressure over time.

How to Fix

1. Make sure the boiler is switched off at the wall.
2. Locate the filling loop and check that both valves are fully closed and disconnected if possible.
3. Bleed a small amount of water from a radiator to lower the pressure.
4. Call a Gas Safe registered engineer if the pressure rises again quickly, as they can replace the faulty valve.

Expansion Vessel Problems

The expansion vessel absorbs pressure changes as water heats up. If it loses its air charge or fails, the system pressure can climb too high when the heating runs.

How to Fix

1. Switch off the boiler and check the cold pressure reading.
2. If the pressure is high when cold, bleed some water to bring it down.
3. Contact a Gas Safe engineer to test the expansion vessel charge pressure.
4. Have the vessel recharged or replaced if it is no longer working properly.

How to Prevent the 117 Error Code on Your Baxi Boiler

Good habits with your heating system can stop pressure problems and keep your boiler running smoothly all year.

Here are some practical steps to prevent the issue:

1. Check the pressure gauge regularly when the system is cold and keep it between 1 and 1.5 bar.
2. Always close the filling loop tightly after use and disconnect it where possible.
3. Book an annual boiler service with a Gas Safe engineer to check the expansion vessel and valves.
4. Get a boiler cover plan for extra peace of mind. At PlusHeat our nationwide plans mean fast help when faults like this appear, helping you avoid bigger repair bills down the line.

Our plans provide prompt engineer visits for both homeowners who want a cosy family home and landlords who need reliable systems for tenants. You will save money on unexpected repairs and enjoy dependable support whenever you need it.

Frequently Asked Questions 

How dangerous is it to run the boiler with a 117 error code?

It is best not to run it at all, as high pressure can strain pipes and seals and may lead to leaks.

Can I fix high pressure myself without calling an engineer?

For simple overfilling you can bleed radiators safely, but repeated faults need professional checks.

Does cold weather affect the chance of seeing the 117 code?

Yes, as temperatures drop the system pressure can change and highlight problems with the expansion vessel.

Will bleeding all radiators solve a persistent 117 fault?

It helps lower pressure temporarily, but if the filling loop or vessel is faulty the error will return.

Is the 117 code different on older Baxi models?

The meaning stays the same across most models, though some show it as E117 on the display.