People often assume a tankless water heater simply replaces the tank in the same spot. In practice, it changes what the plumbing, the gas line, the vent and sometimes the electrical panel have to do.

United Plumbing installs tankless water heaters across Fort Myers, Cape Coral, Estero, Bonita Springs, North Fort Myers, Lehigh Acres and Golden Gate. This guide walks through what is involved so you can compare quotes with confidence. If you are still deciding, read tank vs tankless water heaters and whether tankless suits Florida homes. For problems after installation, see tankless water heater repair.

What A Tankless Installation Involves

Gas Line: Why Sizing Matters

A tankless unit heats water on demand, so it can pull a large amount of gas all at once. The gas line that served a tank heater and your other appliances may not carry enough for a tankless unit, especially over a long run. A licensed plumber calculates the total gas load, the pipe length and material, upsizes the line where needed, and then pressure tests and leak checks the connections.

Gas work is not a DIY job. A mistake can mean poor performance at best and a safety hazard at worst. For the safety side, read our guide to gas water heater warning signs and safety.

Venting: Condensing vs Non-Condensing

Gas tankless heaters have to exhaust combustion gases safely. How they do it depends on the model:

• Condensing units are more efficient and produce a cooler exhaust. They typically use plastic venting specified by the manufacturer, and they produce condensate that needs a drain.
• Non-condensing units run hotter and use venting rated for higher exhaust temperatures.
• Direct vent and outdoor models draw combustion air and exhaust in different ways, and outdoor-rated units are installed on an exterior wall.

The manufacturer's instructions and local code set the vent materials, maximum lengths and the clearances at the termination, such as distances from windows, doors and soffits. Where the unit goes, whether a garage, utility area or exterior wall, shapes the vent route, and Florida heat, humidity and storm season are worth considering when choosing between indoor and outdoor locations.

A tankless installation done to the manufacturer's instructions and local code is a different job from a tank swap. Ask every quote how it handles the gas line, the vent and the water.

Water, Electrical and Condensate

• Service valves: isolation valves on the hot and cold lines let the unit be flushed and descaled, which matters in hard water.
• Relief valve and expansion tank: required protections vary with the system. See expansion tank code and safety.
• Electrical: gas models need power for the controls, while electric tankless units can draw a lot of power and may need a dedicated circuit and enough capacity in the panel.
• Condensate: condensing units need a drain for acidic condensate, often with a neutralizer.
• The water itself: Southwest Florida water is mineral heavy. Treating it protects the heat exchanger. See why descaling matters, the link between hard water and failing water heaters and our water softener options.

What Happens On Install Day

• 1. Shutoff and removal: the water and gas or power are shut off, and the old heater is drained and removed.
• 2. Mounting: the tankless unit is mounted at the planned location with the required clearances.
• 3. Connections: gas, vent, water, condensate and electrical connections are made to the manufacturer's instructions.
• 4. Testing: the gas connections are leak tested, the lines are purged of air and the unit is started.
• 5. Setup: the temperature is set and the unit's operation is checked at several fixtures.
• 6. Inspection and walk-through: permits and inspections are handled where required, and you are shown how the unit works.

Timing depends on the scope, since a straightforward swap is very different from a job that needs a new gas line, new venting or electrical work. Ask for the schedule in writing with your quote. If you are planning how to pay for it, see water heater financing, and for the bigger comparison read whether hybrid heat pump water heaters are worth it.

Sources and Further Reading

• U.S. Department of Energy, tankless or demand-type water heaters: energy.gov
• U.S. Consumer Product Safety Commission, gas water heater safety and recalls: cpsc.gov
• More guides from United: Fort Myers plumbing articles.

About the author: United Plumbing Inc has been the Fort Myers plumber for residential, commercial and new construction customers since 1980. Licensed technicians install tankless water heaters across Fort Myers, Cape Coral, North Fort Myers, Estero, Bonita Springs, Golden Gate and the barrier islands. Florida License CFC 1433130. Head office: 3560 Teeside Lane, Fort Myers, FL 33916. Reviewed by United Plumbing's service management team. Last updated October 2026.