Tankless or tank at a glance
The two designs trade upfront cost against running cost and space.
| Factor | Tankless | Tank |
|---|---|---|
| Typical lifespan | About 20 years with care | About 8 to 12 years |
| Hot water supply | Continuous, limited by flow rate | Limited by tank size |
| Wall or floor space | Small wall unit | Floor space for a 40 to 50 gallon tank |
| Installed cost (typical U.S.) | Roughly $2,500 to $6,500 | Roughly $1,000 to $2,500 |
| Upgrade work | Larger gas line, new vent or heavy electrical | Usually a like-for-like swap |
| Cold water sandwich | Brief cold burst between uses | None |
Costs are typical ranges. The real number depends on your home and comes from a call.
Sizing a tankless unit by flow, not by gallons
A tankless heater is rated in gallons per minute at a temperature rise. A shower runs about 2 gallons per minute, a kitchen faucet about 1.5, and a dishwasher or washing machine about 2. Add up what runs at once to find the demand.
Temperature rise is the gap between incoming water and the 120 F setpoint. Colder incoming water in winter lowers the output, so a unit sized only for summer will disappoint in January. Ask for sizing at the coldest expected inlet temperature.
Signs your home suits a tankless unit
- Hot water runs out when two showers run at once.
- The tank is over 10 years old and due for a swap.
- You have a gas line near the heater that can be upsized.
- The house has room for a vent to the outside.
- The household wants lower standby heat loss.
If most of these do not apply, a standard tank may fit better. See water heater replacement for the like-for-like path.
What an installation visit covers
- 1
Review fuel and location
Gas needs combustion air and a sealed vent. Electric needs spare capacity in the panel.
- 2
Check the gas line or circuit
Many gas units need a larger gas line. Whole-house electric units often need several double-pole breakers.
- 3
Set the unit and isolation valves
Service valves let the heat exchanger be flushed later without cutting pipe.
- 4
Vent, connect and test
The vent is sealed, gas connections are leak-tested and water lines are purged.
- 5
Walk through settings
You see how to set temperature and read error codes.
Soft water and the maintenance schedule
Greenville Water's year-to-date average total hardness for spring 2026 was 5.7 mg/L, which is very soft. Scale forms slowly on a tankless heat exchanger in water like that, so descaling matters less here than in many parts of the country.
Flushing still earns its place. Sediment and debris from the pipes collect in the unit and filter screen, and a yearly flush through the service valves clears them. Follow the maker's interval, and treat the schedule as a plan, not a guess.
What changes tankless installation cost
Most of the spread comes from what the house needs around the unit, not from the unit itself.
Ask your insurer or utility about rebates, since programs change. To get a real quote, call (855) 575-2890 and describe the home.
Code and permit basics for a Mauldin tankless install
South Carolina enforces the 2021 SC Plumbing Code, or the 2021 International Plumbing Code with SC modifications, and local enforcement has been required since January 1, 2023. The 2024 codes have a scheduled effective date of January 1, 2027. A job started near that date should be checked against whichever edition applies.
The City of Mauldin requires a permit before you add, alter or replace any plumbing system, and its Building and Zoning office is at 5 E. Butler Rd, (864) 234-3475. A licensed plumber can pull it. If the job adds new lines, the same permit rule applies, as covered under new plumbing installation.
Source type: SC Building Codes Council and City of Mauldin Building and Zoning.
A gas smell is not a tankless question
If you smell gas near a heater, leave the house and call the gas utility or 911 first. Call a plumber after the area is cleared. If an existing unit shows an error code or leaks, see water heater repair for diagnosis.
Tankless water heater questions from Mauldin homeowners
About 20 years with regular flushing. Tank heaters usually last 8 to 12 years.
Not from storage. It can fall short if too many fixtures run at once for its flow rating, which is why sizing matters.
The City of Mauldin says a permit is required to add, alter or replace plumbing. Confirm with Building and Zoning at (864) 234-3475.
No. Soft water slows scale, but sediment still collects. A yearly flush through the service valves is a good habit, so follow the maker's schedule.
Sometimes. Electric units draw heavy current, and many panels need an upgrade first. A plumber and an electrician can check your panel.
It takes emergencies first, but you can also call to plan a tankless job. Planned work is scheduled for a day that suits you.
Yes. The service area includes Greer and the other nearby towns.