Remeha E.00.40 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha E.00.40 fault code mean?
The E.00.40 fault code on a Remeha boiler indicates that the hydraulic pressure sensor is reporting a reading that falls below its expected minimum threshold, or that the sensor is not responding at all. In plain terms, the boiler cannot confirm that adequate water pressure exists within the system. To protect itself from running dry or overheating, the boiler locks out and halts operation until the underlying cause is identified and resolved. This fault is most commonly seen on the Remeha Quinta Ace range and can stem from genuinely low system pressure, a blocked water filter restricting flow, or a faulty pressure sensor.
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
- Low system water pressure Common
The most frequent trigger for E.00.40 is system pressure that has dropped below the acceptable operating range of 1–2 bar. This can happen after radiators have been bled, following a minor system leak, or if the pressure relief valve has discharged water. The sensor correctly detects low pressure and puts the boiler into lockout as a precaution.
- Blocked or dirty water filter Sometimes
Over time, the boiler's inline water filter can accumulate sludge, scale, or debris from the system. A heavily blocked filter restricts water flow sufficiently to mimic low-pressure conditions at the sensor, triggering the fault even when the headline pressure gauge reading looks acceptable.
- Faulty or incorrectly wired pressure sensor Sometimes
If the pressure is within the correct range and the filter is clean, the sensor itself may have failed, become disconnected, or developed a wiring fault. The boiler interprets a missing or out-of-range signal from the sensor as dangerously low pressure and shuts down. An engineer should also verify the heat exchanger is clean and the system has been properly de-aired before condemning the sensor.
- System airlocks Sometimes
Trapped air pockets within the heating circuit can cause erratic pressure readings and inconsistent flow past the sensor. This is particularly common after recent system work, a power flush, or filling the system from scratch.
- Chemical or solvent contamination Rare
Certain corrosive chemicals or solvents introduced into the heating system can degrade seals, fittings, and sensor components over time, causing leaks or sensor failure that ultimately triggers this lockout code.
How to fix it
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the boiler's display or on the pipework. It should read between 1 and 2 bar when the system is cold. If the needle sits below 1 bar or the display shows a very low figure, low pressure is almost certainly responsible for the E.00.40 fault.
- Repressurise the boiler using the filling loop DIY safe
Switch the boiler off and allow it to cool below 40°C. Open all radiator valves fully. Slowly open the filling loop valve — usually a small lever or tap on the pipework beneath the boiler — while watching the pressure gauge. Once the reading reaches approximately 1 to 1.5 bar, close the filling loop valve firmly. Switch the boiler back on and reset the fault. If pressure rises normally but drops again within a few days, there is likely a leak in the system that needs a Gas Safe engineer to investigate.
- Reset the boiler DIY safe
After repressurising, press and hold the reset button as described in your Remeha boiler's user guide. Allow the boiler to complete its ignition sequence. If the E.00.40 code returns immediately, do not keep resetting repeatedly — move on to the next checks or call an engineer.
- Inspect for visible leaks around the boiler and pipework DIY safe
Check around radiator valves, visible pipework joints, and underneath the boiler for signs of dripping water or damp patches. Even a slow weep can cause pressure to drop gradually. Do not attempt to tighten gas connections yourself, but tightening a dripping radiator valve tail or bleed screw is a straightforward homeowner task.
- Check that all system valves are fully open DIY safe
Ensure all lockshield and thermostatic radiator valves are fully open, and that any isolating valves on the boiler's flow and return pipework are in the open position. Partially closed valves can restrict flow and contribute to pressure-related faults.
- Inspect and clean the water filter (engineer task on sealed systems) Gas Safe engineer
The Remeha Quinta Ace has an inline water filter that can become clogged with system debris. Cleaning it involves isolating the boiler and draining a section of the hydraulic circuit. This should be carried out by a Gas Safe registered engineer who can also check the heat exchanger cleanliness and ensure the system is properly de-aired at the same time.
- Have the pressure sensor tested and replaced if faulty Gas Safe engineer
If system pressure and filter condition are both confirmed as satisfactory but the E.00.40 fault persists, the hydraulic pressure sensor itself is likely defective. A Gas Safe registered engineer will test the sensor's electrical output, check its wiring harness, and replace the sensor if required. The engineer should also inspect the safety relief valve operation during the same visit.
- Call a Gas Safe registered engineer Gas Safe engineer
If the fault code returns after repressurising, or if you are unable to identify an obvious cause, contact a Gas Safe registered engineer. They can carry out a full system diagnosis, check the heat exchanger, test the sensor, and safely resolve any underlying leak or component failure. Always verify an engineer's Gas Safe registration at gassaferegister.co.uk before booking.
Parts you may need
- Hydraulic pressure sensor · from £25
- Filling loop assembly · from £18
- Inline system water filter / strainer · from £20
- Pressure relief valve · from £22
- System inhibitor / sludge remover (for post-repair protection) · from £15
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 £120–£320, depending on the underlying cause.
Frequently asked questions
Can I fix the Remeha E.00.40 fault myself without calling an engineer?
The most common cause — low system pressure — is something you can resolve yourself by repressurising via the filling loop. That costs nothing if you do it yourself, or just a call-out fee if an engineer does it. However, if the pressure keeps dropping, the filter needs cleaning, or the sensor needs replacing, a Gas Safe registered engineer is required. Attempting internal boiler work without Gas Safe registration is illegal and potentially dangerous.
How much does it typically cost to fix the E.00.40 fault in the UK?
For most households, the repair falls between £120 and £320 including parts and labour. A simple pressure sensor replacement with a standard call-out will sit at the lower end of that range. If the engineer also needs to clean the heat exchanger, power flush the system, or address a hidden leak, costs move towards the higher end. Note that labour rates in London and the South East tend to run 20–40% above the UK average. In rare cases where the fault has caused damage to other components such as the PCB, costs can be higher — but that is uncommon for this particular code.
Why does my Remeha boiler keep losing pressure and showing E.00.40?
Recurring pressure loss nearly always points to a leak somewhere in the system — this could be a weeping radiator valve, a dripping joint, a failing pressure relief valve, or, less commonly, a micro-leak within the boiler itself. Repeatedly topping up the pressure without finding the source is not a safe long-term fix, as it gradually dilutes the system inhibitor and can lead to corrosion. Book a Gas Safe engineer to pressure-test the system and locate the source of the loss.
How do I prevent the E.00.40 fault from coming back?
Annual boiler servicing by a Gas Safe engineer is the single most effective preventative measure — it includes checking system pressure, inspecting the water filter, and testing sensor operation. Between services, keep an eye on the pressure gauge and top up if it dips below 1 bar. Make sure the system contains an appropriate dose of corrosion inhibitor, and avoid introducing any chemicals or solvents near the boiler's hydraulic components.