Troubled Waters

Troubled Waters is a Minutemen side quest in Fallout 4.

Detailed walkthrough
After joining the Minutemen, this quest can be obtained when talking to Preston Garvey or listening to Radio Freedom. The Sole Survivor is informed that a robot from Graygarden has sent a message requesting help, and the Minutemen should respond. Alternatively, the quest may be obtained directly from Supervisor White even if the Sole Survivor has not joined the Minutemen.

To proceed with the quest the Sole Survivor must travel to Graygarden and speak with their leader, Supervisor White. After giving a rundown on Graygarden's origins and purpose, White brings up the settlement's water supply, which has degraded significantly since the war. She asks the Sole Survivor to travel to the source, Weston water treatment plant, and try to clean things up a bit.

Upon arriving at the treatment plant the Sole Survivor finds the exterior overrun with Super Mutants. They must fight or stealth their way through to reach the interior of the building and investigate further.

The first interior area is devoid of hostiles and defenses. After taking the elevator to the basement, the Sole Survivor encounters an automated turret. Walking down the stairs ahead of the elevator reveals the trouble with the plant: the majority of it has flooded due to the pumps shutting down.

At this point, the Sole Survivor must fight their way through the mirelurks infesting the plant to activate five pumps: four to lower the water level and one to restore the water supply to Graygarden. There are also several turrets to be dealt with, either by destroying them or deactivating them using the terminal in the room to the right of the elevator. Movement through the plant is gated by electronic doors, which won't open until the water behind them has been lowered by activating the next pump.

After draining the facility and activating the final pump, the Sole Survivor can report back to Supervisor White to receive thanks and a reward of ~100 caps, as well as access to the Graygarden workshop, a discount from Supervisor Greene, and some miscellaneous food items. If the quest was given by Preston Garvey, the Sole Survivor must report back to him to turn in the quest; it will be completed immediately upon receiving the reward otherwise.