The Water Treatment Plant Storage Room key is a key that was added with the most recent patch and wipe for Escape From Tarkov which was 12.12.30.
The key can be found in jackets and on scavs that you kill and it’s for the map Lighthouse, and at the time of making this video, it’s going for about 200k roubles on the flea market. It’s a 40 use key, and it’s description is: A key that opens the storage room, located somewhere at the water treatment plant.
Rogue Farming Video – https://youtu.be/kYPw3z4BtHs
Water Treatment Plant Loot Guide – https://youtu.be/TJ_7M0EvCPA
