Baxi E.02-.07 Fault Code: Causes, Fixes & Repair Costs
What does the Baxi E.02-.07 fault code mean?
The E.02-.07 fault code means your Baxi boiler has detected that the system water pressure has fallen below 0.5 bar — the minimum threshold needed for safe operation. When this happens, the boiler locks out automatically to protect itself and your heating system. This is one of the most frequently reported Baxi fault codes and, in many cases, can be resolved at home simply by topping up the system pressure. However, if pressure keeps dropping after you repressurise, there is an underlying issue — such as a leak or a failing component — that will need a Gas Safe registered engineer to investigate.
General guidance only — not a substitute for professional advice. 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 dropped and needs topping up Common
The most straightforward explanation is that the pressure has simply crept downward over time — perfectly normal in a sealed heating system, especially after summer when the heating has been off for months. If it has only recently dipped below 0.5 bar and there are no obvious leaks, repressurising via the filling loop is usually all that is needed.
- Radiators were bled without repressurising afterwards Common
Every time you bleed a radiator to release trapped air, a small amount of water leaves the system with it. If the pressure was already on the low side, bleeding one or more radiators can be enough to trigger the E.02-.07 lockout. Always top the pressure back up to around 1–1.5 bar (cold) after bleeding.
- Visible leak from a radiator, pipe, or fitting Common
A steady or intermittent drip from a radiator valve, compression fitting, or exposed pipework will gradually drain the system. Check around all visible radiators, under the boiler, and along any accessible pipework for signs of dampness, staining, or corrosion.
- Faulty or weeping pressure relief valve (PRV) Sometimes
The PRV is a safety device that opens to discharge water if system pressure climbs dangerously high. Over time the valve seat can wear or collect debris, causing it to weep continuously even at normal pressures. If you notice water dripping from the discharge pipe outside (typically a 15 mm copper pipe terminating near an outside wall or drain), the PRV may need cleaning or replacing by a Gas Safe engineer.
- Expansion vessel failure Sometimes
The expansion vessel contains a pressurised air charge that accommodates the expansion of water as your system heats up. If the internal diaphragm ruptures or the air charge dissipates, the vessel can no longer do its job and the PRV may release water repeatedly to compensate, causing progressive pressure loss. A Gas Safe engineer can test the vessel charge and recharge or replace it.
- Hidden leak in buried or concealed pipework Sometimes
Pipework routed under floor screed, behind plasterboard, or through ceiling voids can develop pinhole leaks that leave no obvious visible evidence. If you are regularly losing pressure but cannot find a source, a Gas Safe engineer may use pressure testing or thermal imaging to locate the leak.
- Internal boiler seal or joint failure Rare
Seals, O-rings, and pump connections inside the boiler itself can weaken with age, allowing a slow internal drip that collects in the boiler casing. This is more likely on boilers that are ten or more years old and have not had regular servicing.
How to fix it
- Check the pressure gauge on the boiler DIY safe
Most Baxi boilers have a pressure gauge on the front panel or visible through a small window. A reading below 1 bar when the heating is cold confirms the cause of the lockout. The correct cold pressure for most Baxi boilers is 1.0–1.5 bar.
- Locate the filling loop and repressurise the system DIY safe
The filling loop is usually a short braided hose with one or two valves, found beneath the boiler or in an airing cupboard. Slowly open the valve(s) to allow mains water into the system and watch the gauge rise. Stop when it reaches approximately 1.2–1.3 bar. Close the valve(s) firmly. Never overfill above 1.5 bar when cold. Refer to your boiler's user manual if you are unsure of the exact filling loop configuration for your model.
- Reset the boiler DIY safe
Press and hold the reset button (typically on the front control panel) for 3–5 seconds until the boiler attempts to restart. Allow a couple of minutes for it to complete its start-up sequence. If it fires up and the fault clears, monitor the pressure gauge over the next 24–48 hours.
- Check for obvious leaks around radiators and pipework DIY safe
Walk around your home and inspect all visible radiators, particularly at the valves and bleed points. Check under the boiler for any drips or water staining. Look at accessible pipe joints in the airing cupboard, loft, or basement. Even a slow drip is significant — note its location for the engineer.
- Check the PRV discharge pipe outside DIY safe
Find the external discharge pipe for the pressure relief valve (a small copper or plastic pipe, usually exiting through an outside wall close to the boiler). If water is dripping or trickling from it continuously, the PRV is likely weeping and will need attention from a Gas Safe engineer.
- Do not keep repressurising if the pressure drops again DIY safe
If the pressure falls back below 1 bar within 24–48 hours of topping up, there is a leak or a component fault causing water to escape. Repeatedly refilling the system without fixing the root cause can mask the problem and potentially cause damage elsewhere. Stop repressurising and call an engineer.
- Call a Gas Safe registered engineer to diagnose and repair the underlying fault Gas Safe engineer
If the pressure loss recurs, if you have found a leak you cannot easily address yourself, or if you suspect the PRV or expansion vessel is at fault, a Gas Safe registered engineer should carry out a full system pressure test, locate any leaks, and repair or replace the defective components. Do not attempt to work on the PRV, expansion vessel, pump, or any internal boiler components yourself.
Parts you may need
- Pressure relief valve (PRV) · from £25
- Expansion vessel (internal, boiler-specific) · from £60
- Expansion vessel Schrader valve / core · from £5
- Filling loop assembly · from £15
- Radiator valve (pair) · from £18
- System inhibitor (post-repair top-up) · from £12
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–£320, depending on the underlying cause.
Frequently asked questions
Can I fix the Baxi E.02-.07 fault myself?
If the cause is simply low pressure, yes — topping up via the filling loop and resetting the boiler is a safe DIY task that costs nothing. However, if the pressure drops again within a day or two, you have an underlying fault such as a leaking component or a failing expansion vessel, and those repairs must be carried out by a Gas Safe registered engineer. Never attempt to work on the PRV, expansion vessel, or any gas or electrical components inside the boiler yourself.
How often should I need to repressurise my Baxi boiler?
A well-maintained sealed heating system should hold its pressure for many months. Needing to repressurise once or twice a year is not unusual, but if you find yourself topping it up every few weeks — or more — that strongly suggests a leak somewhere in the system or a weeping PRV. In that situation, stop topping up and book a Gas Safe engineer rather than masking the problem.
Water is dripping from a pipe outside my house — is that related to E.02-.07?
Very likely yes. That external pipe is almost certainly the discharge outlet for your pressure relief valve. If it is dripping or running continuously, the PRV may be stuck open or have debris on the seat preventing it from sealing properly. Each time it weeps, water leaves the system and pressure drops — which is exactly what triggers E.02-.07. A Gas Safe engineer can clean or replace the PRV, which typically costs £100–£200 including labour.
Could the expansion vessel be causing repeated pressure loss, and what does replacing it cost?
Yes — a failed expansion vessel diaphragm is a common reason for recurring pressure loss on boilers that are several years old. When the vessel can no longer absorb the thermal expansion of the water, the PRV opens to compensate, and pressure drops after every heating cycle. Recharging the vessel air charge (if the diaphragm is still intact) is a relatively quick job; replacing the vessel entirely typically costs £150–£320 including parts and labour, depending on the boiler model and whether the vessel is internal or external. In rare cases where there is also significant pipework damage or multiple leaks, costs can be higher — your engineer should give you a clear quote before starting work.