Boiler shows E15 and shuts down. There may be water present in the base tray or under the boiler.

Safety first: Turn off power and close the water supply. Water and electricity together are dangerous. Do not operate the boiler with visible leaks.

Step-by-step checks:

• 1. Inspect for water: Remove the front panel and look into the base of the boiler. Check for standing water or damp insulation.
• 2. Check condensate trap: On condensing Viadrus models, inspect the condensate trap and pipe for blockages. Clean the trap and ensure the pipe slopes correctly to the drain.
• 3. Identify leak source: Look at all visible joints: pump unions, heat exchanger connections, automatic air vent, safety valve outlet. Dry the area and observe where water reappears.
• 4. Dry float switch: If the base tray has a float switch, gently sponge out water and allow the area to dry completely. Do not bypass the switch.
• 5. Reset and monitor: Once dry and any obvious minor leaks are tightened, restore power and monitor closely for new leaks.

When to stop: If you cannot locate the leak, or if it comes from the heat exchanger or pump body, contact a heating engineer. Operating with leaks can damage the boiler and property.