Boiler fault codes
Ideal F1 Fault Code: Water Pressure Too Low
Published
Ideal display
F1
What it means
The boiler has measured the water pressure in the heating system as too low to run safely, so it has stopped. Ideal says the pressure needs topping up to between 1 and 1.5 bar.
Safe to check yourself
- Read the pressure gauge on the front or underside of the boiler with the heating off and cold
- Top up to 1 to 1.5 bar with the filling loop, then close both valves fully
- Look for drips at radiator valves, under the boiler and on any pipe you can see
- Check the small copper pipe outside that runs from the boiler through the wall for dripping
- If the boiler does not start by itself after topping up, press the restart button once
Call an engineer if
- F1 comes back within a day or two of a top-up
- The gauge reads normal but F1 stays on the display
- You can see water coming from inside the boiler casing
- The filling loop will not raise the pressure at all
- You smell gas: open windows, turn off the gas at the meter if you can reach it safely, avoid switches, and call the National Gas Emergency Service on 0800 111 999 from outside
An F1 boiler fault on an Ideal means low water pressure. The heating circuit has lost water, the pressure sensor has read the drop and the boiler has shut down to protect itself. In most homes you can clear it tonight by topping up to 1 to 1.5 bar with the filling loop and pressing restart once.
How do I clear F1 on an Ideal boiler?
Turn the heating off and let the boiler cool, because a hot system reads higher than a cold one. Find the filling loop under the boiler. On most Ideal Logic combis it is a short loop under the boiler, worked by two blue handles on the valves underneath, though some installers fit a separate braided hose instead.
Open one valve fully, then open the second slowly and watch the gauge. Stop at 1 to 1.5 bar, the band Ideal gives in its own fault guide. Close both valves firmly and, if the display has not cleared, press restart once. If the hose is detachable, take it off once the valves are shut so the system cannot creep up.
Do not overshoot. The pressure relief valve on these boilers lifts at 3 bar and dumps water through the copper pipe outside, which can leave you back at F1 a few days later.
If the filling loop has been removed and you cannot find it, do not improvise with other fittings. That is the point to book an engineer, see boiler pressure repair.
Why does my Ideal keep going to F1?
A boiler does not use its own water. If you are topping up every few days, water is leaving the system somewhere. In rough order of how often it turns out to be the cause:
- A weeping radiator valve, towel rail or joint under the floor
- The pressure relief valve letting by after being over-filled, visible as a drip from the copper pipe outside
- An expansion vessel that has lost its air charge, so pressure swings high when hot and low when cold
- A leak inside the boiler, often at the heat exchanger or pump seals
- A tired pressure sensor giving a false low reading
When the gauge looks fine but F1 stays
Ideal's own fault-finding chart for the Logic Combi has two checks after the system pressure: are the connections on the water pressure sensor secure, and if they are, replace the sensor. So if your gauge sits at 1.2 bar and the display still says F1, the sensor or its plug is the likely culprit, not the water.
That is inside the casing and is engineer work. The water pressure sensor is one of the cheaper parts in the boiler, usually tens of pounds rather than hundreds. Most of the cost of the visit is labour and finding the cause.
What an engineer does about a repeat F1
On an F1 visit the engineer checks the gauge against a separate test gauge, looks for leaks on the system and inside the boiler, tests the pressure relief valve and checks the air charge in the expansion vessel with the system pressure taken off. Only then do they replace a part.
You pay the £60 call-out to get someone there, and the repair price is agreed with you on site before any work starts. If the fix is only a top-up, that is the whole bill. Gas work is carried out by Gas Safe registered engineers.
For a wider look at pressure that will not hold, see why boiler pressure keeps dropping, or book Ideal boiler repair.
Is F1 the same code on every boiler?
No. The fault letter and number mean different things on different makes, so check the badge on the front before following any guide. On Ideal boilers with a code display, such as the Logic range, F1 is low water pressure. On a Glow-worm it is a different fault, covered on our Glow-worm F1 page.
Questions people ask
Is it safe to use an Ideal boiler showing F1?
The boiler will not run while F1 is showing, which is the safety feature doing its job. Low pressure itself is not dangerous. Top up to 1 to 1.5 bar and restart. If you see water inside the casing, switch off at the fused spur, if the spur is dry, and call an engineer.
What pressure should an Ideal boiler be on?
Ideal gives 1 to 1.5 bar with the system cold. It will rise a little when the heating is running. Anything close to 3 bar is too high and will make the relief valve discharge.
Why does F1 appear after I bleed the radiators?
Bleeding lets air out, and water moves in to replace it, so the pressure drops. Top up again with the filling loop after bleeding. If it keeps happening without bleeding, you have a leak or a failing part.