Water heater is leaking water from the bottom of the casing

Safety: Isolate power and gas. Close the cold water inlet and relieve pressure by opening a hot tap. Water may be hot.

• Remove front cover: Carefully remove the casing and inspect for visible signs of leakage.
• Identify source: Check around the plate heat exchanger, pump unions, safety valve discharge, and hydraulic block for wetness or staining.
• Tighten fittings: Gently tighten any weeping compression joints. Do not overtighten plastic components.
• Replace faulty components: If the plate or primary heat exchanger is leaking from the body, or the hydraulic block is cracked, replace the affected part with a Vaillant-approved spare.
• Check safety valve: If the pressure relief valve is discharging, check system pressure and expansion vessel (if present). Replace the valve if it does not reseat.
• Test for leaks: Re-pressurise and run the appliance while checking for further leakage.