الجواب وبالله التوفيق
It has been documented in Fatawah Darululoom ZakriyahPg. 248, Vol. 6 with reference to Madarij, that Rasulullah Sallallaho Alyhi Wasallam did not drink water immediately after eating.
It is injurious for the stomach and the digestive system to drink water immediately after eating; therefore one should wait for some time before drinking water.
Fatawah Darululoom Zakriyah, reference to Shumail-KubrahPg. 248, Vol. 6
واللہ اعلم بالصواب