How a tankless water heater works
A tankless heater has no storage tank. When a hot tap opens, flow sensors start a burner or elements that heat the water as it passes through a heat exchanger. You get hot water for as long as the tap runs, within the unit's flow limit, and the unit sits on the wall instead of taking floor space.
That design saves space and removes the standby loss of a tank, but it asks more of the house. A gas unit needs a large gas supply and venting that suits its design. An electric unit may need a heavy circuit that an older panel cannot supply.
What the house must provide
Check these before you fall for a model, because an upgrade to the supply can change the budget.
| Item | Gas tankless | Electric tankless |
|---|---|---|
| Fuel supply | Larger gas line than most tanks use | Heavy electrical circuits, often a panel upgrade |
| Venting | Dedicated sealed vent, sometimes through a wall | None needed |
| Water supply | Pressure and flow high enough to fire the unit | Same |
| Condensate | Drain for condensing models | None |
| Maintenance | Descaling, depending on water | Descaling, depending on water |
Thinking about a tankless upgrade?
Call and the plumber will review your gas line, panel and layout.
Water quality and scale
Mineral scale is the enemy of a tankless unit. The narrow passages of the heat exchanger clog, error codes appear, and flow drops. Annual flushing with a descaling solution is the usual remedy, and the schedule depends on your water.
If you are on a private well in Hampstead or Chester, a water test tells you whether hardness or iron is a risk. The New Hampshire health department recommends testing wells for common contaminants on a regular schedule, and the plumber can suggest a filter or softener based on the results. On town water in Derry, the water department at 603-432-6147 can tell you what it reports about your supply.
The install visit
Tankless installs are more involved than tank swaps, so the plumber walks you through the sequence.
- Load calculation. The plumber adds up how many fixtures run at once and confirms the unit's flow rating fits.
- Fuel and vent upgrades. Gas lines are sized or replaced, venting is run and electrical circuits are installed as needed.
- Mount and connect. The unit goes on the wall with isolation valves so it can be flushed.
- Commission. The plumber tests flow, temperature and ignition and shows you the control panel.
Service and flushing
Even a well-installed unit needs service. A flush clears scale, a filter screen cleaning restores flow and an error-code diagnosis finds failed sensors or igniters. If your unit is cold or throws an error, our water heater repair page applies to tankless models too.
Many owners schedule a flush once a year. Others on soft water can go longer. The plumber recommends a schedule after seeing the water and the inside of the unit.
Is a tankless heater right for your house?
These questions help you decide before you call.
- Do you want to free up floor space?
- Is your gas line or electrical panel large enough, or are you willing to upgrade?
- Do you run several showers or appliances at once?
- Is your water hard or high in iron, and are you prepared to maintain the unit?
- Are you planning to stay long enough to recover the extra cost of installation?
Tankless Water Heater questions in Derry
Yes, if the unit is sized for the flow your household needs at the same time. The plumber adds up showers and appliances to choose a model, and some homes use two units.
Often yes for a gas unit, since tankless heaters burn more fuel at once than tanks. The plumber measures the existing line and tells you what is needed.
Usually once a year, though it depends on water hardness. Homes on well water with iron or hardness issues may need more frequent flushing.
Repair calls for a tankless heater that has stopped heating are taken 24/7. Planned installs are scheduled during regular working hours.
It can, by removing standby losses, but the savings depend on your usage and fuel prices. We do not promise a specific amount.
References: manufacturer installation instructions for gas, venting and electrical needs. Derry Water Department, 603-432-6147. NH DHHS and NHDES private well testing brochure.
Hot water without a tank
Call to plan a tankless water heater install in Derry.