6 minute read
Boiler low pressure fault codes: F22, F1, E119 and F75 explained
Different makers, different letters, mostly the same message: there is not enough water pressure in the heating for the boiler to run. Clearing the code is usually easy. What matters is whether it comes back.
The codes at a glance
| Code | Boilers | What it means | First thing to try |
|---|---|---|---|
| F22 | Vaillant | Low water pressure in the system | Repressurise to the level in the manual |
| F1 | Ideal, including Logic, Logic Max and Logic+ | Low water pressure | Repressurise to the level in the manual, then reset |
| E119 | Baxi and Potterton combis | Low boiler pressure | Repressurise, then reset |
| F75 | Vaillant | No pressure change seen when the pump starts | Check the gauge; if it is fine, call a Gas Safe engineer |
Codes change between models and years, so treat this table as a guide and your manual as the authority. Other makes use their own codes for the same thing. If your boiler is not listed, the manual will have a fault code table, and the gauge will tell you whether the pressure is actually low.
Vaillant F22
F22 means the water pressure in the heating has dropped significantly. The boiler shuts down or will not fire, and you have no heating or hot water until it is fixed. The usual causes are a leak in the heating system, radiators that have just been bled, or less often a faulty pressure sensor or worn parts in the boiler.
Top the pressure up following the manual (the general method is here) and check around pipes, radiators and valves for any sign of water. If the code clears and then comes back, and you can see no leak, the water is going somewhere you cannot see.
Ideal F1
On Ideal boilers such as the Logic range, F1 is low water pressure. ADI's F1 guide puts the normal reading between 1 and 2 bar; check your manual for the figure your model wants when cold. The causes are the same family: a leak in the pipework or radiators, a faulty water pressure sensor giving a false low reading, a pressure relief valve letting water out, or recently bled radiators.
One cause is easy to miss. A power flush pushes water hard through old pipework, and it can break away corrosion that was holding a weak spot together. If F1 appeared soon after a power flush, tell whoever you call.
Baxi and Potterton E119
E119 is low pressure on Baxi and Potterton combis. The display may show it as E119, E1 19, E11 9 or E 119; they are all the same fault. Repressurising is a job you can do yourself. If the pressure drops again afterwards, that is a strong sign of a leak on the boiler, the pipes or the radiators. If repressurising does not clear the code at all, a Gas Safe engineer should look inside the boiler.
Vaillant F75
F75 is related but different. When the pump starts, the boiler expects to see a small change in pressure. If it sees none, it stops and shows F75. That can be a seized or failing pump, a faulty pressure sensor, trapped air, or sludge blocking the flow, as well as a system so low on water that there is nothing to measure. You may hear humming or clicking at start-up, and the gauge may read zero or not move at all.
If the gauge is low, top it up. If the gauge is fine and F75 persists, it is a boiler fault for a Gas Safe engineer rather than a leak.
When a code keeps coming back
Clearing a low-pressure code once is routine. Clearing it every few days means the heating is losing water. The pressure relief valve pipe outside is the first thing to check, then every radiator valve. If both are dry, the leak is most likely in pipework under a floor or inside a wall, and that is what thermal imaging, tracer gas and pressure testing are for. Where the water goes when you cannot see a leak.
Code back again?
Tell the office the code, the boiler make and how often it comes back. If it is a leak, they will book an engineer to find it; if it sounds like a boiler fault, they will tell you that too.
Quick answers
What does F22 mean on a Vaillant boiler?
Low water pressure. The pressure in the heating system has dropped too far for the boiler to run safely. Topping up usually clears it; if it comes back soon after, the system is losing water.
What does F1 mean on an Ideal boiler?
Low water pressure, on models such as the Logic, Logic Max and Logic+. Top the pressure up to the level in your manual and reset the boiler. If you are doing it more than once or twice a year, get the cause found.
What does E119 mean on a Baxi or Potterton boiler?
Low boiler pressure. The display may show it as E119, E1 19 or E 119. Repressurising clears it; if the pressure drops again, that points to a leak on the boiler, pipes or radiators.
Is F75 a low pressure fault?
Not exactly. On a Vaillant, F75 means the boiler did not see the pressure change it expected when the pump started. The cause can be the pump, the pressure sensor, air in the system or sludge, as well as a leak. It usually needs a Gas Safe engineer.