Again, we need contexts, but I'll try a simple reply:
"Agua de beber" is drinking water. The preposition denotes the purpose of the water.
- Aquí siempre hay que hervir el agua de beber.
We always boil the water we drink.
- Se encontró presencia de microplásticos en el agua de beber.
There were microplastics found in drinking water.
- El agua de beber se obtiene de pozos administrados por el Estado.
Drinking water is obtained from State-owned wells.
"Agua a beber" is the water to be drank for some purpose.
- El agua a beber al día depende de tu actividad física.
The water you need to drink every day depends on your physical activity.
- Tienes que hervir el agua a beber, si no está limpia.
You must boil the water you are going to drink if it's not clean.
- Si das agua a beber a tus mascotas, no les des agua mineral.
If you give your pets water to drink, don't give them mineral water.
__________________
♪ ♫ ♪ Ain't it wonderful to be alive when the Rock'n'Roll plays... ♪ ♫ ♪
|