This is the 14749th most frequent Russian word.
питьевого
"Питьевого" means "drinking" or "potable," typically referring to water fit for consumption.
In this sentence, 'питьевого' again qualifies 'источника' (source), indicating the water from the source is drinkable.
Рядом с домом расположен источник питьевого источника.
Near the house, there is a source of potable water.
Here, 'питьевого' (potable) describes 'воды' (water), specifying that it is drinkable.
Для хорошего здоровья важно пить достаточно питьевого воды.
For good health, it is important to drink enough potable water.
Here, 'питьевого' modifies 'водоснабжения' (water supply), emphasizing its suitability for drinking.