Restore the water pressure is an objective in Water Supply in the Division.
Walkthrough
Deal with the one on the ground floor because they can move around very easily. After that, make a dash toward the stairs in the Eastern part of the room leading upwards. The Cleaner who is on the balcony uses a Flamethrower. While they have long range, you can outdistance it easily enough and stay out of its range. You can also fire on the Cleaner with the Flamethrower to provoke them.
This pressure Valve is found just to the East of the Central Pressure Valve. Hacving dealt with the Cleaners, head over to it and interact with it. This will get the progress gauge moving again. You just need to hold out a short while after that.
You will have one final wave of Cleaners coming in after you. They will come from the Eastern doorways.
