Ideal F1 fault codewhat it means and how to fix it
System pressure has dropped below the minimum the boiler will run at. Topping it back up to 1.2 bar usually clears it straight away.
Take care
How often are you having to do this?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
First time in a year or more
Normal slow loss. Top up to 1.2 bar, reset, and think no more about it.
More than twice in six months
That is a leak. Every refill introduces oxygenated water, and that is what produces the black sludge that ruins pumps and radiators.
Book a leak trace instead of topping up again.
It will not hold pressure for a day
Loss that fast usually means water is going somewhere you have not found yet, and there is a real risk of damage under a floor or in a ceiling.
Turn the boiler off and get someone out rather than refilling repeatedly.
What F1 means
F1 is Ideal signalling low water pressure in the sealed heating circuit. The boiler measures pressure continuously and refuses to fire below roughly 0.5 bar, because a heat exchanger running without enough water passing through it is destroyed within minutes. The lockout is protection working correctly. The real question is where the water went, because a sealed system does not use water up. If the gauge is falling there is a leak, a failed expansion vessel, or a safety valve passing. Topping up gets your heating back tonight; finding the loss stops you doing it again next month.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Water escaping from a buried joint | Under floorboards or behind a bath panel, where it soaks away without ever marking a ceiling. The rate of loss is what tells you it is happening. | Common |
| Air removed from radiators and not replaced | Every bleed screw you open takes volume out. Work round a whole house on a Saturday morning and the needle will have moved by lunchtime. | Common |
| Expansion vessel no longer holding its charge | The tell is a normal cold reading that shoots up once the heating runs, then sits low again afterwards because the excess went out of the safety valve. | Occasional |
| Safety valve not reseating | Grit on the seat holds it fractionally open. Look for the copper pipe through the outside wall — if it drips or has a white streak below it, that is your answer. | Occasional |
What to try yourself
Wait until the system is cold before reading anything. A gauge read straight after the heating has run will flatter you by a couple of tenths.
On a Logic the filling loop is usually a braided hose under the appliance. On a Logic Max there is often a built-in filling key instead — a small plastic tab that slots into the underside.
Open it gently. Ideal appliances fill quickly and the needle covers the last half bar faster than feels comfortable, so keep your hand on the valve.
Stop at 1.2 bar. Past 2.5 bar cold the safety valve lifts, dumps water outside, and you are back to a low reading with a wet wall for company.Shut the loop, then hold the reset button until the display clears. Call for heat and check it fires.
Put the date on a sticky note by the appliance. What matters is not this reading but the gap until the next one.
Get a Gas Safe registered engineer to look at your Ideal F1
Gas Safe Register engineers only. No obligation.
What it costs to fix
Typical repair cost
£0–£450
Time on site
10 minutes
Nothing if it just needs topping up. Leak trace £90–£160, expansion vessel £150–£280, and up to £450 if floors have to come up.
Typical UK prices including parts and labour, updated August 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Expansion vessel (8 litre, sealed system)
EV-8L£35–£85Plumbing merchant
Price checked 5 August 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 5 August 2026
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related Ideal fault codes
- F.22Get it checkedThe boiler has shut down because there is not enough water in the system. Pressure has dropped below roughly 0.5 bar and it will not fire until you top it up.Related: water pressure
- F.75Get it checkedThe boiler cannot detect a rise in pressure when the pump starts, so it has locked out. Usually a failed pressure sensor or a pump that is not moving water.Related: water pressure
- CE 207Get it checkedSystem water pressure has dropped too low for the boiler to run safely. Topping the system back up to 1.2 bar usually clears it in five minutes.Related: water pressure
- E10Usually simple to fixSystem water pressure has fallen too low for the appliance to fire. Top the system back up to 1.2 bar and it will restart.Related: water pressure
- 108Usually simple to fixThe heating circuit does not contain enough water to run safely. Refill through the filling loop to about 1.2 bar and the code clears.Related: water pressure
- E119Get it checkedSystem pressure has fallen below the level the boiler will operate at. Refilling to 1.2 bar and resetting usually clears it in a few minutes.Related: water pressure
Related guides
Common questions about Ideal F1
What pressure should an Ideal Logic run at?
Between 1.0 and 1.5 bar with the system cold, and 1.2 bar is the number to aim for. It will read higher when the heating has been running, which is normal. Always set it cold.
Where is the filling loop on an Ideal Logic?
Usually a braided hose beneath the boiler with a small valve at each end. On Logic Max models there is often a built-in filling link operated with a plastic key at the base of the appliance. If you cannot see either, ask an engineer to point it out once.
Will F1 clear on its own?
No. F codes on Ideal boilers are latched lockouts — the boiler holds them until the condition is fixed and it is reset. If the code cleared by itself, check the gauge again, because the pressure may be sitting right on the threshold and moving either side of it.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
- Interviews with working engineers
Checked by Technical reviewer (Gas Safe registration to be displayed on appointment) on 5 August 2026.