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
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
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 September 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 28 September 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Ideal fault codes
- H AGet it checkedA temporary code with two meanings. On an Isar it is low water pressure and Ideal say fill to 1 bar; on a gaugeless Mexico HE, Ideal send you to the radiator valves.Related: water pressure
- L2Stop — call an engineerThe boiler failed to detect a flame during ignition and has locked out on the gas valve. Do not keep resetting it.Related: same brand
- F2Get it checkedThe flame was lost during operation. Ideal direct you to check the gas supply first, and that is genuinely the right order.Related: same brand
- L1Get it checkedThe boiler is not seeing enough water flow through it to run safely, so it has stopped. Usually a pump, an air lock, or a blocked filter.Related: same brand
- F3Get it checkedThe fan is not running at the speed the boiler expects, so it cannot confirm the flue is clearing and has stopped the burner firing.Related: same brand
- FDGet it checkedNo water flow has been detected. The pump is the prime suspect and this will become an overheat if it is left.Related: same brand
Own an Ideal boiler? Save it and its codes come first next time.
Related guides
Common questions about Ideal F1
What pressure should an Ideal Logic run at?
Ideal publish the range rather than a single figure: check the gauge reads between 1 and 1.5 bar with the system cold. Aiming at 1.2 puts you in the middle of their range with room either side. It will read higher once the heating has run, which is expansion doing what it should. 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.
My boiler shows F01, not F1. Is that a different fault?
It is the same fault. Ideal print this code both ways depending on which vintage of user guide you have — one gives F1, F2 and F5, another gives F01, F02 and F05, for the same appliances with the same remedies. Nothing has changed but the padding. Either form finds this page.
Will F1 clear on its own?
It can, and that is the difference between an F and an L on an Ideal. The L codes are the latched lockouts, held until you press Restart; an F is the same class of fault in a state the boiler can come out of by itself once the condition goes away. So an F1 that has vanished usually means the pressure is sitting right on the threshold and drifting either side of it, which is worth taking as seriously as a code that stayed put.
Should I call Ideal or a local engineer?
Ideal answer this themselves and the answer turns on your warranty. Every row of their fault table says to contact Ideal if the appliance is under warranty, and a Gas Safe registered engineer if it is outside the warranty period. Their consumer helpline is printed in the user guide. For a pressure top-up neither is needed — this is on the short list of things their guide asks you to do yourself.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
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
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.