Error D.22

Safety precautions

1. If you smell gas, leave the property immediately, do not operate electrical switches or the boiler, and call your gas emergency number and a Gas Safe engineer.

2. Turn off electrical isolation at the boiler if you will be working under it and before you remove any covers (basic external panel access for the filling loop is usually fine without removing internal covers).

3. If you are unsure or uncomfortable at any point, stop and call a Gas Safe registered engineer.

Initial checks a homeowner can do

1. Confirm what is displayed: press any control button to wake the display and note if the code shown is D.22 (diagnostic for hot water demand) or an F-code (fault). If an F-code is present (for example F22) follow fault guidance below and consider professional help if unsure.

2. Check whether a hot tap or shower is open (D.22 will show when there is a DHW demand). Close the tap and see whether the display returns to standby or heating mode.

3. Check the boiler pressure gauge on the front panel. For a cold system the normal range is about 1.0–1.5 bar. If pressure is below ~0.8–1.0 bar the boiler may lockout for low pressure (often shown as F22).

4. Look for visible leaks around the boiler, pipework, radiators and underfloor manifolds. Frequent pressure loss suggests a leak or a failing expansion vessel.

Specific diagnostic and fix steps (DHW demand or low pressure related)

1. If you only see D.22 and hot water is flowing/being demanded: this is normal — the boiler is responding to a hot water call. If you expect hot water but none is delivered, proceed with the checks below.

2. If the boiler will not fire and you see a low-pressure fault (F22) or the system pressure is low (<1.0 bar): repressurise the system using the filling loop.

a. Locate the filling loop: on EcoTEC Plus models it is usually a built-in flexible silver hose with two isolation valves under the boiler. Some models have two separate taps/valves. Consult the boiler front flap area; the filling loop may be behind a small service flap.

b. Wake the display so you can watch pressure. With the boiler powered, open the valve(s) slowly (usually turn to inline/open) and listen for water entering. Keep one hand on the valve and watch the pressure gauge. Do not force anything — open slowly.

c. Stop filling when pressure reaches about 1.2–1.5 bar (check your boiler manual for the recommended cold pressure). Close both valves fully and ensure any manual levers show “closed” if labelled. Remove or secure any flexible filling hose if it is removable.

d. Return to the boiler display. If the fault was pressure-related the error should clear and the boiler should resume operation. If the boiler is still locked out, try a reset: press and hold the power/reset button for about 5 seconds (follow your boiler front-panel guidance). Only reset once or twice; repeated resets without resolving the underlying issue are not advised.

3. If pressure keeps dropping after repressurising, check radiators and pipework for leaks and bleed any radiators that recently had air removed (bleeding can cause a pressure drop). If you cannot find a leak or pressure continues to fall, do not keep repressurising repeatedly — contact a Gas Safe engineer because this can indicate a concealed leak, faulty filling valve, or a failed expansion vessel.

4. If D.22 appears but the boiler shows other fault codes (F27, F29, F75 etc.) or the boiler attempts to ignite then locks out: check the obvious things first — gas supply (other gas appliances working?), condensate pipe (frozen or blocked in cold weather), and power supply to the boiler. If basic checks do not fix it, call a professional.

When to call a professional

1. Call a Gas Safe registered engineer if you: detect a gas smell, cannot find or stop a leak, the boiler repeatedly loses pressure, the boiler will not ignite after repressurising and resetting, error F-codes persist, or if you are not confident performing the filling loop steps.

2. Persistent or recurring issues (pressure loss, pump or sensor faults, diverter valve problems, expansion vessel failure) require diagnostic tools and gas-safe handling — these must be handled by a qualified engineer.

Final notes

A standalone D.22 that simply indicates hot water demand is normal and not a fault. If you see F22 or the boiler has locked out due to low pressure, topping the system up to around 1.2–1.5 bar will usually restore operation. If the fault keeps returning or any other fault codes appear, arrange for a Gas Safe registered engineer to inspect and repair the boiler.