Vaillant Three Way Diverter Valve Repair Kit 0020020015. Part No. 0020020015. Alternatively you can check your boiler manual. Vaillant ecoTEC plus 824 VUW 246/5-5 R1 (GC No. 47-044-40). Vaillant ecoTEC plus 831 VUW 316/5-5 R1 (GC No. 47-044-41).
eBay