Intergas 0.0 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas 0.0 fault code mean?
The 0.0 fault code on an Intergas boiler indicates that the central heating system pressure has dropped below the minimum threshold the boiler needs to operate safely. The PCB monitors water pressure continuously, and when it detects a reading that is too low — typically under 0.5 bar — it triggers a lockout to protect internal components such as the pump and heat exchanger from running dry. You will usually see the boiler completely stop working alongside this code. Correct operating pressure for an Intergas boiler is between 1.0 and 1.5 bar, with 1.3 bar being the ideal target.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- System pressure has simply dropped over time Common
Central heating systems naturally lose a small amount of pressure over months of use. If you have not topped up the system recently and the gauge reads below 1.0 bar, low pressure alone is likely triggering the 0.0 code. This is the most common and straightforward explanation.
- Leak in the pipework or at a radiator Common
Even a very slow drip — at a radiator valve, a towel rail joint, or along the pipework — can cause pressure to fall steadily. If you top up the system and the pressure drops again within a few days, a leak is almost certainly present. Check around radiator valves and visible pipework for damp patches or corrosion staining.
- Air trapped in the system Sometimes
Airlocks in radiators or the pump can give a false low-pressure reading and prevent correct circulation. Bleeding radiators starting on the ground floor and working upward releases trapped air, though doing so will also reduce pressure slightly and may require a top-up afterwards.
- Pump seal failure causing an internal leak Sometimes
The seals inside the circulation pump degrade with age. A failing seal can cause a small but persistent internal leak inside the boiler casing, reducing system pressure without any visible external drip. This also risks water reaching nearby electrical components.
- PCB water damage from an internal leak Rare
If water from an internal leak — such as a weeping pump seal or a cracked heat exchanger — reaches the PCB, the board can be damaged or start misreading sensor data. In this scenario the 0.0 code may persist even after pressure is restored, because the PCB itself is compromised.
How to fix it
- Check the pressure gauge reading DIY safe
Locate the pressure gauge on the front of the boiler or on the pipework beneath it. If the needle sits below 1.0 bar — or is at zero — low pressure is confirmed as the immediate cause. Take a note of the reading before doing anything else.
- Top up system pressure via the filling loop DIY safe
Find the filling loop — usually a short braided-metal hose with one or two valves, located beneath the boiler. Slowly open the valve(s) and watch the pressure gauge rise. Stop when the needle reaches 1.3 bar. Close the valve(s) fully. Never overfill beyond 1.5 bar. If you are unsure where the filling loop is, consult your boiler handbook.
- Bleed the radiators to clear any airlocks DIY safe
Starting on the ground floor, use a radiator bleed key to open each bleed valve slightly until water (not air) trickles out, then close it. Work through all radiators and towel rails, moving upstairs last. After bleeding, re-check the pressure gauge and top up again to 1.3 bar if it has dropped.
- Reset the boiler once DIY safe
After restoring correct pressure, press and hold the reset button for a few seconds as described in your boiler's handbook. Allow the boiler to complete its ignition sequence. If the 0.0 code reappears within a short time, do not keep resetting — this indicates an underlying problem that needs an engineer.
- Monitor pressure over the following 48 hours DIY safe
If pressure drops again quickly after topping up, this strongly suggests a leak somewhere in the system. Check around radiator valves, visible pipework joints, and beneath the boiler for any sign of moisture or corrosion. Note how fast the pressure is falling, as this information will help an engineer diagnose the issue.
- Contact a Gas Safe registered engineer to investigate further Gas Safe engineer
If the fault code returns, pressure keeps dropping, or you cannot identify the source of the problem, a Gas Safe registered engineer must be called. They will pressure-test the system to locate any leaks, inspect the pump and its seals, check the PCB for water damage using appropriate test equipment, and carry out any necessary repairs before resetting the boiler safely.
Parts you may need
- Circulation pump (replacement) · from £80
- Filling loop assembly · from £15
- Radiator bleed key · from £3
- PCB (printed circuit board) · from £280
- Pressure relief valve · from £20
- Magnetic system filter (e.g. Magnaclean) · from £55
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £80–£350, depending on the underlying cause.
Frequently asked questions
Can I just keep topping up my Intergas boiler pressure to clear the 0.0 fault?
Topping up pressure is the right first step, but if the pressure drops repeatedly — say, more than once every few weeks — you have a leak that needs professional attention. Repeatedly refilling without fixing the root cause can introduce excess oxygen into the system, accelerating internal corrosion and eventually damaging the heat exchanger or pump. Get an engineer to trace and repair the leak.
How much does it cost to fix an Intergas 0.0 fault in the UK?
If the fix is simply topping up pressure, it costs nothing beyond a plumber or engineer call-out fee of roughly £80–£120. A pipework or radiator valve leak repair typically costs £100–£250. A pump replacement usually falls in the £150–£350 range including labour. In the uncommon scenario where the PCB has suffered water damage, a replacement board can cost £300–£450 fitted. A full boiler replacement, which is only necessary when the boiler is beyond economic repair, is a separate conversation and significantly more expensive.
Why is my Intergas boiler losing pressure even though I cannot see any leaks?
Internal leaks inside the boiler casing — particularly from a weeping pump seal or a micro-crack in the heat exchanger — are invisible from the outside. Water can drip onto the PCB or drain internally without ever appearing on the floor. A Gas Safe engineer can remove the casing, pressure-test the system, and inspect internal components to find leaks that are not visible during a normal household check.
Is it safe to use my Intergas boiler while it is showing the 0.0 code?
No. When the boiler locks out on the 0.0 code it is protecting itself from running with insufficient water pressure. Operating a boiler with low pressure risks damaging the pump and heat exchanger, both of which are expensive to replace. Restore pressure to 1.3 bar and attempt a single reset. If the lockout returns, leave the boiler off and call a Gas Safe engineer rather than repeatedly resetting it.