Replacing a tankless unit is not the same job as converting from a tank
People search for tankless replacement cost and mean one of two things. Some already own a wall-hung unit that has failed, and they want the same kind of heater back. Others own a tank and want to switch. The second job costs more in almost every home, because the plumbing around a tank was never built for a tankless unit.
A like-for-like swap often reuses the gas line, the vent run, the water connections and the isolation valves already on the wall. The plumber mostly removes, mounts and reconnects. A conversion usually means a bigger gas line, a different kind of vent, a condensate drain for some units, and new hot and cold stubs at a different height.
Ask any plumber quoting you which job they believe it is, and why. If the quote does not say whether existing gas and venting will be reused, it is not a real quote yet. The honest answer sometimes arrives only after someone looks at the wall.
The cost drivers, from biggest swing to smallest
Gas line capacity
A tankless burner draws a large burst of gas all at once. If the existing pipe was sized for a tank, a licensed plumber may need to run larger pipe, and that means opening walls or running it along a basement ceiling.
Venting type and route
Some units vent through plastic pipe out a side wall. Others need a different material or a longer run. Every elbow and every foot of vent adds material and labor, and a roof or tight chase adds more.
Unit size and features
A heater sized for one bathroom and a kitchen is a different machine from one sized for a large family with a soaking tub. Recirculation features, condensate handling and app connectivity all change the equipment line on the quote.
Condition of what is already there
Old shutoff valves that will not close, corroded fittings, or a failed pressure relief discharge line all get replaced while the wall is open. These are small items individually and they add up.
Access and disposal
A heater in an unfinished basement is easier to work around than one in a finished closet or garage corner. Hauling away the old unit and any drywall patching are line items worth asking about.
Cost to replace is only part of the picture. Homeowners policies often cover sudden water damage from a failed heater but usually not gradual leaks or wear, so check your own policy. For a real number on your house, call us and a licensed plumber can describe what they would need to see first.
Three common replacement scenarios and what each tends to involve
| Starting point | Usually reused | Usually new or changed |
|---|---|---|
| Tankless to same type of tankless | Gas line, vent run, wall mounting area, water stubs | Isolation valves if worn, vent fittings if brittle, condensate fittings, a fresh pressure relief discharge line |
| Tank to tankless | Cold supply, sometimes the location | Gas pipe size, vent material and route, hot and cold stubs, condensate drain, electrical outlet for the unit |
| Old tankless to a different size or model | Some piping, the general location | Gas sizing review, vent compatibility check, new valves, possible recirculation line |
| Tankless to a new tank | Gas line, water lines, vent may need a different type | Drain pan, strap anchoring, flue connection, expansion handling a plumber confirms |
The last row surprises people. Going backward from tankless to a tank is a real option when a household decides the maintenance or the cold-water gap is not worth it. It costs differently, but it is not free of its own conditions, so the same rule applies: ask what is being reused.
Want a tankless quote that lists what it reuses?
Call the 24/7 line and a licensed plumber can walk through your gas line, vent and wall layout, then give you a clear price before work starts.
What Riverton homeowners should know
Riverton buys its drinking water wholesale from Jordan Valley Water Conservancy District. Riverton's 2022 water quality report lists average hardness of 190 mg/L, with a range of 174.5 to 202.5 mg/L, which works out to about 11 grains per gallon. That is the figure to use for planning a descaling routine, and it is a 2022 number, so newer Riverton reports may differ.
The practical step is simple. Ask Riverton's water division for its latest annual water quality report, test your own tap with a hardness strip, and plan to flush a tankless unit on a schedule your plumber sets. Hard water does not ruin a tankless heater overnight, but scale is the usual reason performance slips.
Sources: Riverton City 2022 water quality report, Riverton City culinary water page
Why descaling belongs in the cost conversation
A tankless unit heats water as it passes through a narrow heat exchanger. Dissolved minerals in that water can leave scale on the inside of the exchanger. Scale acts like insulation, so the unit works harder, the outlet temperature can wobble, and an error code may appear. Scale builds faster in harder water.
Riverton's own water report lists hard water, and the section at the bottom of this page has the numbers. In practice that means a tankless unit here is not a fit-and-forget appliance. When you compare a quote, check whether it includes isolation valves with service ports. They let a plumber flush the unit with a descaling solution without cutting any pipe.
If your last unit died young, ask the plumber to look at the exchanger and the inlet screen before you buy the same model again. A failure caused by scale is a maintenance story. A failure caused by a cracked exchanger from freezing or a bad vent is a different story, and the replacement plan should change with it.
A fair way to decide between replacing the unit and repairing it
Lean toward repair
- The unit shows an error code tied to a sensor, igniter or inlet screen
- Hot water turns lukewarm, but the heat exchanger has never leaked
- Flushing has never been done and scale is the likely cause
- The unit is otherwise young and the vent and gas are sound
Lean toward replacement
- Water is leaking from inside the cabinet or exchanger
- Repeated failures after repairs, with scale returning fast
- Vent pipe is cracked, discolored or sagging, which is a safety issue
- Parts for an older model are hard to source, and the quote for the repair rivals a new install
Our tankless water heater service covers both paths, and a plumber can tell you honestly which side your unit falls on after looking at it. If the answer is a failed tank rather than a tankless unit, the water heater replacement page explains that job and what drives its price.
Questions that expose a thin quote
Is the existing gas line adequate?
A good answer names the pipe you have and what the new unit needs. A vague answer means the number may change later.
What vent material and route will you use?
You should hear where the vent exits and why. Gas appliance venting is a safety item, not a place to improvise.
Are service valves included?
Isolation valves with ports make later flushing simple. Without them, descaling is harder and often skipped.
What happens to the old heater?
Removal and disposal should be on the quote, along with any wall patching you are expected to handle yourself.
Who confirms the permit question?
Permit rules vary, so a plumber should tell you to ask the Riverton building department what your job needs, rather than say yes or no from memory.
Where this advice applies beyond Riverton
Cost structure is the same in nearby towns, but water quality and local permit habits are not. If you live west of us, we also dispatch to Herriman, and Herriman posts its own water information, so compare it before assuming your scale rate matches ours. South of Riverton, Bluffdale publishes a 2024 water quality report with a hardness average close to Riverton's, and its permit guidance is separate, so call that city's building office for your job.
Rules and sources behind this page
Tankless replacement follows the plumbing code Utah adopts, plus the manufacturer's gas and venting standards. Utah Code 15A-2-103 adopts the 2024 International Plumbing Code (IPC) as the state plumbing code, effective July 1, 2026, with Utah amendments on top.
According to Riverton's 2022 water quality report, average hardness was about 190 mg/L, roughly 11 grains per gallon. Scale is one reason tankless units need periodic flushing.
Tankless replacement questions homeowners ask
Usually the scope differs, not the markup. One quote may assume the old gas line and vent will be reused, while another includes larger gas pipe, new venting and valves. Ask each plumber to list what is reused and what is new, and compare like with like.
A quote with no scope at all is the riskiest one, because the changes show up after work begins.
Often it does when the home had a tank, because tankless burners draw more gas at once. A licensed plumber has to size the line against the unit's rating and the other gas appliances on it. We do not guess from the street, we measure what is installed.
Gas connections and venting are not DIY jobs. A leak or a bad vent can mean carbon monoxide or a gas release. If you smell gas, leave the building and call Enbridge Gas Utah at 1-800-767-1689 or 911 first, then call a plumber.
Swapping a water-only fitting is something some homeowners handle, but the unit itself belongs to a licensed plumber.
There is no single schedule. It depends on your water and the unit's maker. In hard water, plumbers commonly flush more often, and a service port valve set makes it a quick visit. Your plumber can set an interval after inspecting the exchanger.
It depends on your household. Tankless units remove the standby tank and give a long run of hot water, but they cost more up front and need descaling. Our replacement team can compare both options against your gas line and space before you decide.
Yes. Older homes sometimes need a different vent path, a larger gas line, or both, and we look at what is on the wall before quoting. We do not assume the age of your house tells us what is behind the drywall.
Riverton's 2022 water report lists hard water, which is why scale management matters here. Other towns publish their own reports, so check yours before assuming the same schedule. Testing your own tap is the quickest way to know.