Keston E44 Fault Code: Low Water Pressure Lockout
The E44 code on Keston boilers signals that the system water pressure has fallen below the acceptable threshold — typically under 0.5 bar. When this happens, the boiler shuts itself down as a protective measure and will not restart until the pressure is restored and the boiler is manually reset. You can confirm the fault by checking the pressure gauge on the boiler's front panel; a reading below 1 bar confirms low pressure is the culprit.
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.
What does the Keston E44 fault code mean?
The E44 code on Keston boilers signals that the system water pressure has fallen below the acceptable threshold — typically under 0.5 bar. When this happens, the boiler shuts itself down as a protective measure and will not restart until the pressure is restored and the boiler is manually reset. You can confirm the fault by checking the pressure gauge on the boiler's front panel; a reading below 1 bar confirms low pressure is the culprit.
Common causes
- Gradual pressure loss over time Common
All sealed central heating systems lose a small amount of pressure naturally, especially after radiators have been bled or following a prolonged period of inactivity. This is one of the most routine reasons for an E44 code and is often a straightforward fix via the filling loop.
- Leak somewhere in the heating system Common
A steady or repeated drop in pressure that keeps returning after topping up strongly suggests water is escaping somewhere — whether from a radiator valve, a pipe joint, or a component inside the boiler itself. Look for damp patches around radiators, visible drips under the boiler, or watermarks on pipework. Do not simply keep refilling without investigating, as an ongoing leak can cause damage to floors, walls, and boiler internals.
- Air trapped in the system Sometimes
Air pockets in the heating circuit can interfere with pressure readings and contribute to the system behaving as though it is under-pressurised. Bleeding the radiators may release this air, but doing so will also reduce system pressure, so a top-up via the filling loop afterwards is usually needed.
- Faulty pressure relief valve (PRV) Sometimes
The PRV is designed to release water if pressure climbs dangerously high, but a valve that is worn or stuck partially open will let water escape even at normal pressures. If you notice water dripping from the overflow pipe outside your property, a failing PRV is a likely cause. This component requires a Gas Safe engineer to assess and replace.
How to fix it
- Check the pressure gauge on the boiler DIY safe
Look at the built-in pressure gauge on the front of your Keston boiler. A healthy system sits between 1 and 1.5 bar when cold. If the needle is below 1 bar — or in the red zone — low pressure is confirmed as the cause of the E44 code.
- Inspect for visible leaks before doing anything else DIY safe
Have a look around your radiators, underneath the boiler, and along any exposed pipework for signs of dripping, damp patches, or watermarks. If you spot an active leak, do not repressurise the system — call a Gas Safe engineer first, as topping up a leaking system will only cause further damage.
- Repressurise via the filling loop DIY safe
If there is no sign of a leak, locate the filling loop — usually a silver braided hose with one or two valves beneath the boiler. Slowly open the valve(s) and watch the pressure gauge climb. Stop when the gauge reaches approximately 1 to 1.5 bar, then close the valve(s) firmly. Never exceed 2 bar, as over-pressurisation will trigger a different fault and cause the PRV to discharge water.
- Reset the boiler DIY safe
Press and hold the reset button (often marked with a spanner or flame symbol) for around 3 to 5 seconds. The boiler should attempt to fire up. Do not reset more than two or three times — repeated unsuccessful resets without a fix can mask a more serious underlying problem.
- Monitor pressure over the following days DIY safe
Keep an eye on the pressure gauge over the next week or so. If the reading remains stable, the issue was simply routine pressure loss. If the pressure drops again — particularly within a short time — there is almost certainly a leak or a faulty component that needs professional attention.
- Call a Gas Safe registered engineer with Keston experience Gas Safe engineer
If the E44 code returns after repressurising, if you found signs of a leak, or if the boiler still fails to restart, you need a qualified engineer. Keston boilers use a twin-flue arrangement and a modulating pump, which make them more complex than most domestic boilers — when booking, specifically ask whether the engineer has worked on Keston appliances before. They will be able to trace and repair leaks, test or replace the pressure relief valve, and carry out any further diagnostics safely.
Parts you may need
- Filling loop assembly · from £25
- Pressure relief valve (PRV) · from £35
- Radiator bleed valves (set) · from £15
- Pressure gauge · from £20
- System inhibitor fluid (for topping up after repair) · 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 £100–£350, depending on the underlying cause.
Frequently asked questions
Can I repressurise my Keston boiler myself to clear the E44 code?
Yes, in most cases topping up the pressure via the filling loop is a straightforward task a homeowner can do safely. The key caveat is that you should check for any visible leaks first — if water is escaping somewhere, repressurising without fixing the source will only delay the problem and could cause damage. If pressure drops again within a short period after topping up, stop and call a Gas Safe engineer.
How often should a Keston boiler need repressurising?
Occasional pressure loss — perhaps once or twice a year, particularly after bleeding radiators — is perfectly normal. If you find yourself topping up the system every few weeks, or if the pressure gauge drops noticeably within days of repressurising, that frequency points to an underlying leak or a failing component such as the pressure relief valve. This warrants a professional inspection rather than repeated top-ups.
Why does my Keston boiler need a specialist engineer — can't any Gas Safe engineer fix an E44?
Any Gas Safe registered engineer is legally qualified to work on your boiler, but Keston appliances use a twin-flue system and a modulating pump that differ from mainstream brands like Worcester Bosch or Vaillant. Some engineers are less familiar with Keston's layout and components, which can lead to longer diagnostic times and errors. Asking specifically about Keston experience when booking can save both time and money.
Could the E44 code be caused by something more expensive than a simple leak?
In the majority of cases the fault is resolved by repressurising or fixing a minor leak, costing anywhere from around £100 to £350 depending on the location and nature of the leak. However, if the pressure relief valve needs replacing you might be looking at £100 to £200 including labour, and in rare situations where a heat exchanger is cracked and leaking internally, costs can rise to £500 or more. An engineer will be able to identify which scenario applies before committing to any repair.