Overview
Error E.02 – .07 on a Baxi 200/400 combi boiler means the boiler has detected no or very low system water pressure (less than about 0.5 bar). The boiler will lock out to protect itself from running without sufficient water, which would risk pump damage, dry firing or overheating. This is a common, usually non-dangerous fault code that most often indicates the system simply needs topping up (repressurising) or that there is a leak or other issue causing the pressure to fall. Severity is low when the cause is just a routine pressure drop — you will lose heating and hot water until pressure is restored, but there is no immediate safety emergency. It is often a DIY fix to repressurise the system if you are comfortable operating the filling loop and following safety steps. However, if the pressure falls repeatedly, you find a leak, the filling loop will not raise the pressure, or you see signs of water escaping, you must call a Gas Safe registered engineer because the fault may be a leaking pipework, a faulty pressure relief valve, a damaged expansion vessel or an internal boiler fault that needs professional repair.
Possible Cause: No or low system water pressure. system pressure less than 0.5bar
Troubleshooting Steps
Safety precautions:
- If you smell gas, do not touch the boiler; leave the property and call the gas emergency number. Do not attempt any repairs.
- Turn off electrical power to the boiler at the isolator or mains before touching valves or pipework if you are unsure — switching the boiler to standby/off is normally sufficient for repressurising, but isolating power is safest for beginners.
- Work when the system is cold or has been off for a while. Pressure readings rise when the system is hot; topping up when hot can over-pressurise the system.
- Have a towel or bucket handy in case there is a small drip. Keep children and pets away from the area.
Initial checks a homeowner can do:
1. Look at the pressure gauge or digital pressure readout on the boiler. If it reads below 0.5 bar (or shows the low-pressure error), the boiler will not operate.
2. Visually check for obvious leaks around the boiler, pipework, radiators and underfloor/visible pipes. Note any water on the floor or wet pipework.
3. Check that radiators aren’t full of air (cold tops) — bleeding radiators can reduce system pressure further, so if you have just bled the system the pressure may need topping up.
4. Verify mains water to the property is on (open an outside tap) and that any external stopcock feeding the boiler is open.
How to repressurise the boiler (generic steps) — only proceed if no leak is visible and you are comfortable doing this:
1. Identify the filling loop: this is either a flexible braided hose with a valve at each end or an integrated green Easyfill valve under the boiler, depending on model. If your boiler has an integrated Easyfill follow the manufacturer instructions for that control.
2. Turn the boiler to stand-by/off (follow manufacturer guidance). Make sure central heating controls are off and the system is cold.
3. If your filling loop is a removable hose, ensure both valves on the loop are closed before attaching it. If a removable hose is required by your boiler, only use the correct hose supplied/approved for the system. If you do not have the hose or are unsure how to attach it, stop and call an engineer.
4. Open the filling valve(s) slowly. If there are two valves, open the mains-side valve first and then the boiler-side valve very slowly to allow mains water into the system. Watch the pressure gauge carefully.
5. Increase pressure to the recommended operating range. Aim for roughly 1.0–1.5 bar when the system is cold (some guidance allows up to 2 bar). Do not exceed 2–2.5 bar. Stop when you reach the target pressure.
6. Close the filling valve(s) tightly (if using a temporary hose, remove it and store it safely). If your filling loop is a permanent pipe with an integrated valve, ensure the valves are fully closed after filling.
7. Turn the boiler back on and check the display. Many boilers clear the error automatically once pressure is restored; if not, use the reset procedure on the boiler (press and hold the reset button per the manual, usually 5–10 seconds).
8. Run the heating and hot water to check the system operates and re-check the pressure after the pump has run for a short while.
If pressure will not rise when you open the filling loop:
- The filling loop valves may be closed or faulty, the mains feed to the filling loop may be turned off, or there may be a blockage. Stop and call a Gas Safe engineer if you cannot get mains water into the system.
After repressurising — what to watch for and next steps:
- Check for leaks under the boiler, at radiator valves, and along visible pipework over the next 24–48 hours. If the pressure falls again, there is likely a leak, a faulty pressure relief valve (PRV) or an internal boiler fault (expansion vessel failure). Call a Gas Safe engineer.
- If you had to remove a temporary filling hose, never leave it connected permanently. A permanently open connection to mains water can cause uncontrolled over-pressurisation and flooding.
- Do not keep resetting the boiler repeatedly if the fault persists. Repeated lockouts indicate a problem that needs professional diagnosis.
When to call a professional (Gas Safe engineer):
- Repeated pressure loss after repressurising.
- Visible leaks, water coming from the PRV discharge pipe, or wetness under/around the boiler.
- You cannot raise the pressure using the filling loop or you are unsure which valve to operate.
- The boiler still shows the error after you have correctly repressurised and reset it.
Common underlying faults an engineer will check: leaking radiator or pipework, faulty filling loop/isolating valves, defective pressure relief valve, failed expansion vessel, pump faults, or a faulty pressure sensor/PCB. If the problem is more than a simple repressurise, a Gas Safe registered engineer must carry out the repair.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi 200 / 400 Combi Gas Boiler.