What this covers
A tankless water heater heats water only as it is used, so it never runs out and does not keep a tank hot all day. It is sized by flow rate and the temperature rise needed in the local climate, not by gallons. Installation is more involved than swapping a tank: a gas unit usually needs a larger gas line and new sealed venting, an electric unit added circuits, and a condensing model a condensate drain. The plumber mounts the unit, pipes it with isolation valves for future service, installs the vent and fuel connections, and sets the output temperature. Careful work includes checking gas pressure under full load.
When to call
- A household that runs out of hot water with back-to-back showers or a large tub.
- A tank heater due for replacement where floor space is tight.
- A remodel or addition that moves or adds bathrooms.
- A wish to lower standby energy use.
What to expect
- AssessFlow needs, gas line capacity, venting path and electrical service are checked.
- UpgradeGas piping, venting or circuits are upgraded where the unit requires it.
- InstallThe unit is mounted, piped with isolation valves and connected to vent and fuel.
- CommissionThe system is tested under load and the temperature set.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
Is hot water really unlimited?
Within the unit's flow rate, yes. Run more fixtures at once than it is sized for and the temperature drops, which is why sizing to peak use matters.
Why does it need a bigger gas line?
A tankless unit draws several times the gas of a tank heater while it runs. An undersized line starves the burner and the unit short-cycles or errors.
Does it need maintenance?
Yes. Scale builds up in the heat exchanger, so periodic descaling through the isolation valves keeps the unit efficient, more often in hard-water areas or with a softener added.
Related: Water heater installation · Water softener installation · Gas line installation · All plumbing
This page describes what the service involves. The company you hire sets the scope, the schedule and the price, and your contract is with that company. We verify credentials and collect reviews from real jobs. We do not guarantee any company's workmanship. Safety steps are general guidance. When in doubt, leave the home and call 911.