Two licenses for gas work
The Maryland State Board of Plumbing licenses plumbers and gas fitters as separate trades. Swapping a gas water heater touches both, so the crew needs someone holding each license, and many Maryland professionals carry the pair. Counties and Baltimore City issue the permits themselves and inspect venting, the gas connection and the relief valve line.
Water and housing across Maryland
Baltimore and much of its county drink soft-to-moderate water from Piedmont reservoirs, while parts of the Eastern Shore and Southern Maryland rely on wells with more iron and hardness. Older rowhouses and colonials often vent heaters through masonry chimneys that need a draft check after a furnace upgrade. Across the state, most single-part repairs land between $175 and $650, and a standard gas tank replacement runs roughly $1,600 to $3,300; see water heater replacement.