Vaillant Diverter Valve – Refurbished | Part No. 252457

When a Vaillant combi boiler stops producing hot water on demand, defaults to heating only, or begins switching erratically between modes, a worn or seized diverter valve is frequently the cause. Part No. 252457 is the later-generation Vaillant diverter valve, used across a wide range of ecoTEC Plus, ecoTEC Pro, and ecoFIT models. As the valve's internal seals age and the spindle accumulates limescale, the valve can stick partially open, fail to actuate fully, or develop a slow internal bypass that reduces DHW output and heating efficiency simultaneously. The Vaillant Diverter Valve (Part No. 252457) is the correct OEM replacement for fully restoring combi operation.

This is a professionally refurbished genuine Vaillant component. Each valve is fully stripped — all internal seals, O-rings, and the valve spindle are inspected and replaced where required. The valve is reassembled, pressure-tested for hydraulic integrity, and electrically function-cycled through multiple actuation sequences to confirm full-travel, positive switching in both directions before dispatch. The 252457 is the direct replacement for the earlier 178978 on many models, offering a wider compatibility range across the ecoTEC product family.

Compatible Boiler Models

OEM Quality. Proven Performance. Backed by Warranty.

Every refurbished Vaillant diverter valve in our range is pressure-tested and cycle-verified before dispatch. This 252457 valve restores positive, reliable CH-to-DHW switching, eliminates stuck-valve and bypass-leak symptoms, and returns the boiler to full combi operation. As the updated replacement for the earlier 178978 design, it offers improved seal longevity on applicable models. Supplied with a full 12-month warranty.

Delivery & Returns

Orders placed before 1:00 PM (Mon–Fri) are dispatched the same working day, with standard (2–3 working days), next-day, and Saturday delivery options available at checkout. Returns are accepted within 30 days, provided the item is unused and in its original packaging.

Note: Please confirm that part number 252457 matches your existing valve before ordering. On some models this part supersedes 178978 — check your boiler's current parts list if unsure. Installation must be carried out by a Gas Safe registered engineer to ensure safety compliance and warranty validity.