Altitude matters
Gas water heaters burn in thinner air along the Front Range, from Denver at about 5,280 feet to Colorado Springs at over 6,000. Heaters must be approved for high altitude or adjusted so the burner gets the right mix of gas and air. A heater set up for sea level can burn rich, soot up and produce more carbon monoxide. Tankless units also lose some capacity at elevation, so they need to be sized with altitude in mind.
Snowmelt water
Most Front Range cities draw on mountain snowmelt, which is soft to moderately hard. Sediment builds more slowly than in much of the West, though suburbs on groundwater and the plains to the east can have harder water. Winter inlet water in the low 40s means tanks recover slowly from December to March.
Licensing, permits and costs
Colorado licenses plumbers through the State Plumbing Board. Cities and counties issue permits for water heater replacement. Typical repairs run $150 to $650, and a standard gas tank replacement usually costs $1,600 to $3,400. See water heater replacement for details.
Each Colorado city below has its own page covering water, altitude notes and permits.