Overview
The E117 error on a Baxi GA range boiler indicates that the boiler has detected system water pressure above its safe operating tolerance. On these boilers the normal cold static pressure should be around 1.0–1.6 bar (commonly 1.5 bar). When pressure rises into the red zone the boiler flags E117 to protect components and prevent unsafe operation. High pressure can be caused by adding too much water through the filling loop, a filling loop that is not fully closed (or has a slow let-by), a failed pressure relief valve (PRV), a faulty or de-pressurised expansion vessel, or the normal thermal expansion of water when the heating is on when those safety devices are not working correctly. Severity ranges from moderate to serious: one-off mild overpressure can often be resolved by bleeding radiators, but persistent or large overpressure can damage seals, cause leaks or trigger continuous PRV discharge. Any work involving gas, the PRV, expansion vessel or internal boiler parts should be carried out by a Gas Safe registered engineer. For many homeowners the first response is DIY (checking the gauge, bleeding radiators, ensuring the filling loop is closed). If pressure returns to the correct range and the boiler runs normally the error will usually clear. If pressure won’t drop, the PRV is discharging, pressure rises excessively when the system heats, or the filling loop is suspected faulty, stop using the boiler and call a qualified engineer to diagnose and repair the underlying fault.
Possible Cause: System water pressure high
Troubleshooting Steps
Safety precautions:
1. If water is leaking from the PRV pipe or you see active leaks from the boiler, switch the boiler off and isolate electrical supply at the fused spur or consumer unit. Do not attempt internal boiler repairs yourself. Contact a Gas Safe registered engineer.
2. Only attempt radiator bleeding and simple external checks. Do not tamper with gas components, the PRV, expansion vessel or internal boiler parts unless you are a qualified engineer.
3. Allow the system to cool before bleeding radiators to avoid scalding from hot water.
Initial visual checks homeowners can do:
1. Look at the pressure gauge on the front of the boiler when cold. A healthy cold reading is about 1.0–1.6 bar (commonly 1.5 bar). If it is well above 2 bar the system is over-pressurised.
2. Check the PRV discharge pipe (usually a small copper pipe leading outside or to a safe drain) for signs of water dripping — a continuous drip indicates the PRV is operating or leaking.
3. Locate the filling loop (braided hose) under the boiler and confirm both valves are fully closed. If you previously topped the system up, the filling loop must be closed fully.
4. Note whether pressure rises a lot when you turn the heating on. A small rise (~0.2–0.5 bar) is normal due to water expansion; a rise greater than ~0.5 bar suggests an expansion vessel or PRV problem.
Step-by-step diagnostic and basic fix steps you can safely do:
1. Turn the central heating off and allow the system and radiators to cool before working on them. Switch the boiler off at the isolating switch or fused spur.
2. Check and record the cold pressure on the boiler gauge. If it is below, within, or above the 1.0–1.6 bar range, note the value.
3. Bleeding radiators to reduce pressure:
a. Gather a radiator key (or screwdriver if needed), a cloth and a small container.
b. Start with the radiator furthest from the boiler; place the cloth and container under the bleed valve.
c. Insert the key or screwdriver and turn the valve anticlockwise slowly. You will hear hissing as trapped air escapes. When water, not air, starts to flow in a steady stream, close the valve by turning it clockwise.
d. Check the boiler pressure after bleeding radiators. Repeat bleeding other radiators until the pressure on the boiler gauge is around 1.0–1.6 bar (aim for about 1.3–1.5 bar cold).
4. If the pressure remains high after bleeding radiators, confirm the filling loop valves are fully closed. Slight leaks/let-by at the filling loop can keep adding water and raising pressure.
5. If you previously used the filling loop to top up and the pressure is too high, ensure the filling loop is shut off and bleed radiators until pressure reduces to the correct level.
6. Once the pressure is correct, switch the heating on and watch the pressure gauge while the system warms. Expect a small increase; if pressure rises more than about 0.5 bar when heating on, note this as it suggests a problem with the expansion vessel or PRV.
When to stop and call a professional:
1. If the PRV discharge pipe is continuously dripping or pouring water, switch the boiler off and call a Gas Safe registered engineer—do not block or attempt to repair the PRV yourself.
2. If the pressure does not come down after bleeding radiators, or the pressure keeps rising repeatedly, the filling loop may be faulty, the expansion vessel may have lost its pre-charge, or the PRV may be failing. These require an engineer to inspect and repair.
3. If you are unsure where the filling loop or PRV is, or you do not feel confident performing the checks above, switch the boiler off and call a qualified engineer.
4. Any work that involves replacing the PRV, repressurising or recharging the expansion vessel, or internal boiler repairs must be carried out by a Gas Safe registered heating engineer.
Notes and final advice:
1. The E117 fault will typically clear when system pressure returns to the correct range, but if it reappears you must get a professional to find and fix the root cause.
2. Take photos of the pressure gauge and any visible leaks before the engineer arrives — this can help diagnosis.
3. Do not provide or request cost estimates here; arrange a visit from a Gas Safe engineer for a full inspection and safe repairs if the fault persists.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi GA Range.