Wet food only and add water to his food. Maybe do broths too. My cats were on a purina ur st/ox kibble and that made them drink more but they had problems with crystals.
Beyond that the only suggestion I have is to get a wifi motion activated security camera for the litter box. That'll give you advance warning for this sort problem potentially before it gets to be a full on blockage.
Beyond that the only suggestion I have is to get a wifi motion activated security camera for the litter box. That'll give you advance warning for this sort problem potentially before it gets to be a full on blockage.