looking for professional to service my water system in Hang Dong (closed well, submersible pump, & filter).

first step: clean filter, replace materials (sand, gravel, etc.)

appreciate your recommendations.

You could try one or both of the following

On Hang Dong road, on the left heading out of town, about 100m past the entrance to Airport Plaza. A big pump tank establishment.

On the Middle Ring Road, on the left and about 75m before the entrance to Global House. A smaller pump establishment

best of luck