Army MOS 12K is a plumber who performs plumbing and pipe fitting activities on military installations and in the field.
Their duties include:
Installing and repairing pipe systems and plumbing fixtures
Installing water supply and distribution systems
Preventive maintenance on water supply systems
Installing and maintaining heating systems
Installing waste water pipe systems
Connecting pipe sections using valves, couplings, reducers, and other fittings
Army buildings and equipment all require pipe systems for water, steam, gas, and waste. Army plumbers are responsible for installing and repairing these systems.
The 12 Series MOS is a list of occupations under the Army Corps of Engineers.