Controller indicates E18; condensate drain fault (on condensing Danstoker boilers).

Safety: Condensate is mildly acidic; wear gloves and eye protection. Isolate power before working on internal components.

• Inspect condensate trap: Locate the condensate trap at the base of the heat exchanger. Remove and clean out sludge or debris. Refill with clean water before reassembly.
• Check drain line: Ensure the condensate pipe has continuous fall to the drain and is not kinked or frozen. Thaw gently if frozen and insulate as needed.
• Test level switch: If fitted, check the condensate level switch or sensor for free movement and clean any scale.
• Flush system: Pour clean water through the condensate drain to confirm free flow to the drain.

After clearing, reset the boiler. If E18 returns, the level switch or wiring may need replacement.