Vaillant F22 fault code: low pressure

Vaillant F22 means the water pressure in your heating system has fallen below the normal range, which Vaillant gives as 1 to 1.5 bar. Look at the pressure gauge on the front of the boiler. If it reads under 1 bar and you can find the filling loop, topping the system up often takes a few minutes. Vaillant says you can do it without an engineer if you are competent.

What the Vaillant F22 fault code tells you

Vaillant F22 is a pressure fault, not a gas or ignition fault. The boiler has checked the water in the sealed heating circuit and found too little of it. Expect no heating until the pressure is back.

A sealed system can lose a little pressure over time, and bleeding a radiator, a small leak or a recent repair can all push it below the limit. One low reading is a nuisance. A reading that keeps falling means something is wrong.

How to clear Vaillant F22

For a Vaillant F22, the maker’s advice is to restore the pressure slowly, using the filling loop, until the gauge sits inside the normal range. The exact position of the loop, and the reset button or sequence, differ between Vaillant models, so use your boiler manual. Vaillant publishes manuals through its literature finder.

1. Read the gauge. Note the number before you touch anything.
2. Find the filling loop. Your manual shows where it is and how it opens.
3. Open it slowly and watch the gauge rise.
4. Close it as soon as the needle is back in the normal range. Do not overshoot.
5. Reset the boiler as your manual describes.

Resetting often clears a fault, Vaillant says, or gets the boiler working again for a while. If the code comes back, stop repeating the reset.

When Vaillant F22 keeps coming back

If you top up and find the pressure gone again within days, the water is going somewhere. A leak on a radiator valve or a joint, a pressure relief valve that is discharging and a failing expansion vessel are the usual suspects, and the filling loop fixes none of them. A Gas Safe registered engineer can find the cause, and the sooner they do, the less damage the water does.

Vaillant’s guidance also says that where the gauge already reads above the lower limit and the fault stays, it is a case for a Vaillant engineer. If your boiler is still under guarantee, ring Vaillant first so that the visit does not affect your cover.

Safety when you see Vaillant F22

Vaillant strongly advises against opening the boiler casing, because the inside is dangerous. Stay at the filling loop and the controls. If you ever smell gas, the manufacturer’s instruction is to leave the property at once and call the National Gas Emergency Service on 0800 111 999. Do not switch anything on or off on your way out.

Other Vaillant codes you might see

F22 is the pressure code. Flame and ignition faults show as F28 and F29, and Vaillant lists simple checks for those too. Our guide to boiler fault codes explains how to read a code, what to check before you call anyone and which codes are an engineer’s job straight away.

When repeated faults mean a new boiler

A single F22 is not a reason to replace a boiler. A boiler that has several faults in a winter, whose parts are getting hard to find or whose repair bill is heading towards the price of a replacement is a different matter. A like-for-like combi boiler swap is the cheapest replacement, and our combi boiler prices page shows what each type and model costs fitted.

If you do get quotes, put them side by side with our compare tool so that the make, the warranty and what is included can be checked line by line. When you are ready, you can get free quotes from local Gas Safe installers.

Source: Vaillant, boiler fault codes. Read on 3 November. Vaillant’s guidance is used at your own risk, and it accepts no liability for it.