Tankless Water Heaters

How a Tankless Water Heater Works

A tankless unit doesn’t store hot water. It sits idle until you open a hot tap. A flow sensor inside detects water moving through the unit and tells the control board to fire the burner (on a gas model) or energize the heating elements (on an electric model). Water passes through a heat exchanger, picks up heat, and leaves at the temperature you set.

Close the tap and the unit shuts down. There’s no tank sitting in the garage keeping 40 or 50 gallons warm all day, which is where the energy savings come from. The tradeoff is that the unit can only heat so much water at once. That limit is measured in gallons per minute (GPM), and every rating depends on how many degrees the unit has to raise the incoming water.

If you’re comparing options, our water heater services page covers standard tank units too. Plenty of households are better off with a tank, and we’ll tell you if yours is one of them.

The Upside and the Real Limitations

What you gain

• Continuous hot water as long as demand stays inside the unit’s GPM rating. You won’t run a tank dry after the third shower.
• Lower standby energy loss, since nothing is being kept hot between uses.
• A wall-mounted unit about the size of a carry-on suitcase, which frees up floor space in a garage, closet or utility room.
• A longer expected service life than most tank heaters when the unit is maintained.

What you give up

Tankless isn’t magic. Run two showers, the dishwasher and the washing machine at once and an undersized unit will drop temperature or cut flow. Most units need a minimum flow, often around half a gallon per minute, before they fire at all, so a trickle at the bathroom sink may never get hot. You may notice a short burst of cold water between hot cycles, and the wait for hot water at a far fixture doesn’t go away just because the heater changed.

Installation also costs more than swapping a tank for a tank, because the gas line, venting or electrical service often has to change. And scale is hard on these units. If your water is hard and nobody flushes the heat exchanger, performance drops and parts wear out early.

Is Tankless Right for Your House?

We start with a few practical questions before recommending anything.

How many people and fixtures run at the same time

Household size matters less than peak use. A couple who showers at different times can get by with a smaller unit. A family of five that runs two showers and a laundry load every morning needs more capacity, sometimes two units linked together.

What fuel is available

Natural gas lines don’t reach every neighborhood in Southwest Florida. Many homes here are all-electric, and some use propane. That one fact often decides which type of tankless is realistic.

How much electrical capacity you have

Whole-house electric tankless units draw a lot of current. An older home on 100-amp service usually can’t support one without a service upgrade. Even on 200-amp service, we check the load calculation before promising anything.

If the answers point away from tankless, that’s fine. A well-sized tank or a heat pump water heater may serve you better. We can walk you through those too, and the rest of our home services are on the residential plumbing page.

Gas vs Electric Tankless

Gas units (natural gas or propane)

Gas tankless heaters deliver the most flow and are the usual pick for whole-house use. The catch is fuel supply. A large unit can be rated near or above 200,000 BTU per hour, which is far more than a typical tank heater. The existing gas line is often too small, and some installs need a move to a higher-pressure gas system with regulators at the appliances. Propane works well, but the tank, regulator and line all have to be sized for the heater’s full demand.

Electric units

Electric tankless units need no venting and no gas line, which makes them simpler to place. The hurdle is power. A whole-house electric model can pull somewhere in the range of 75 to 150 amps at 240 volts, spread across two to four dedicated double-pole breakers with heavy-gauge wire. That can mean a panel or service upgrade and a licensed electrician. Smaller electric units for a single sink or bathroom are much easier to support.

Our warm inlet water helps electric units more than it would up north, but it doesn’t erase the electrical requirements.

Sizing: Flow Rate and Temperature Rise

Sizing comes down to two numbers. The first is the total GPM of the fixtures you expect to run at once. A shower might use around 2 GPM, a kitchen faucet a bit less, and a washing machine a similar amount. Add up the realistic worst case, not every fixture in the house.

The second is temperature rise, which is the difference between the water coming in and the temperature you want out. Here’s where Southwest Florida has an advantage. Groundwater in Florida generally runs somewhere in the low to high 70s, so bringing water up to about 120 degrees takes a rise of roughly 40 to 50 degrees. In colder states the same unit might need to add 70 degrees or more, which cuts its flow a lot.

So a unit that looks marginal on a spec sheet written for northern climates may do fine here. We still size for your actual peak, and we look at the manufacturer’s flow chart at your expected inlet temperature instead of guessing.

What a Tank-to-Tankless Conversion Involves

Replacing a tank with a tankless unit is more than a swap. Here’s what usually changes:

• Gas line: we check pipe size and length back to the meter or propane tank. Undersized gas piping is one of the most common reasons a new tankless unit underperforms.
• Venting: gas units need their own vent. Condensing models can often vent through PVC or similar plastic pipe. Non-condensing models run hotter exhaust and need metal venting rated for it.
• Condensate: condensing units produce acidic water that needs a drain route, and many installs add a neutralizer before it goes to the drain.
• Electrical: gas units need a standard outlet for the controls. Electric units need dedicated high-amp circuits.
• Water piping: new connections, isolation valves for future descaling, and a pressure relief valve.
• Location: many Florida installs go on an exterior wall, which avoids long indoor vent runs. Garages and utility closets work too with the right clearances.
• Permit: water heater replacements and conversions typically require a permit and inspection from the local building department.

If you’re doing a bigger project, it’s easier to fold the conversion into remodel plumbing work while walls and lines are already open. For new homes, we plan the gas line, venting and water heater location during new construction plumbing so nothing has to be retrofitted later.

Whole-House vs Point-of-Use Units

A whole-house unit feeds every fixture from one location. That’s the common setup and it’s what most people picture.

Point-of-use units are small heaters installed close to a single fixture or group of fixtures, often under a sink or in a closet near a bathroom. They make sense for a far-off guest bath, an outdoor kitchen, a pool bath, or an addition where running a long hot line isn’t practical. They cut the wait for hot water at that spot and waste less water down the drain.

Some homes use both: a main heater for most of the house and a point-of-use unit where the run is too long. We’ll look at your layout before suggesting one or the other.

Hard Water, Scale and Descaling

Much of Florida’s water comes from limestone aquifers, and a lot of it is hard. Private wells in particular can carry heavy mineral content. When hard water gets heated, calcium and magnesium drop out and coat the inside of the heat exchanger. Scale acts like insulation, so the unit works harder, temperatures swing, and eventually it throws an error or shuts down.

How descaling works

A properly installed tankless unit has isolation valves on the hot and cold lines with service ports. To descale, we close the valves, hook up a small pump and hoses, and circulate a descaling solution or white vinegar through the heat exchanger for about an hour. Then we flush with fresh water, clean the inlet screen, and put the unit back in service.

Most manufacturers call for flushing at least once a year. With hard water, more often is common. If your unit was installed without isolation valves, we can add them so future maintenance is quick. A water softener or scale-reduction system upstream can also help stretch the time between flushes.

Recirculation and Hot Water Wait Times

A tankless heater doesn’t shorten the time it takes hot water to travel from the heater to your faucet. In a long, single-story Florida ranch, that trip can take a while, and the unit adds a few seconds of its own to fire up.

Recirculation fixes that. Some tankless models have a built-in pump. Others work with an external pump and either a dedicated return line or a crossover valve under the farthest sink that uses the cold line as the return. Pumps can run on a timer, on demand from a button or motion sensor, or learn your household’s schedule.

We generally steer people toward on-demand control instead of running the pump around the clock, which wastes energy and adds wear. If your hot water lines are old or undersized, it may be worth looking at whole-house repiping at the same time.

Common Tankless Problems and Error Codes

Every brand uses its own error codes, but most problems fall into a few groups.

Flow problems

If the unit won’t fire at a low-flow fixture, the demand may be under the activation threshold. A clogged inlet screen, a failing flow sensor, or a partially closed isolation valve can cause the same symptom at every tap.

Ignition and flame failure

Gas units that click but won’t light often point to low gas pressure, an undersized gas line, an empty propane tank, a dirty flame rod or a bad igniter.

Scale and overheating

Scale buildup can trigger overheat or heat exchanger codes and cause temperature swings. Descaling solves many of these.

Venting and combustion air

Blocked vents, insect nests, improper vent material or a blocked condensate line can shut a unit down. These are safety issues and shouldn’t be bypassed.

If you see water around the unit or under the slab near it, that needs a look right away. Our leak detection service can track down hidden leaks, and our plumbing repairs service handles valve, fitting and line fixes.

A Practical Maintenance Schedule

Tankless units can last a long time, with many rated for roughly 20 years, but only if they’re looked after. Here’s a reasonable routine for most homes:

• Every few months: clean the cold water inlet screen, especially on well water.
• Once a year: descale and flush the heat exchanger. Go more often with hard water.
• Once a year: check vent terminations, condensate lines and the neutralizer on condensing units.
• Once a year: check gas connections for leaks and confirm the unit fires cleanly.
• As needed: test the pressure relief valve and look over isolation valves for drips.

Keep the owner’s manual and model number handy. Manufacturer warranties often have maintenance and installation conditions, so skipping flushes can cause problems with a claim later.

Elevated, Flood-Zone and Seasonal Homes

In flood-prone areas, where the heater goes matters. Local rules in flood zones often require equipment to be at or above a set elevation. A wall-mounted tankless unit is easier to mount high than a floor-standing tank, which is one reason it suits raised homes on the islands and along the coast. We keep this in mind for homes around Fort Myers Beach and the canal neighborhoods in Cape Coral.

Seasonal homes are a good fit too. A tankless unit isn’t sitting there heating water for months while you’re up north. Before you leave, shut the water off at the main, and consider turning off gas to the heater. When you get back, run each hot tap for a minute to clear air and check for leaks. If the unit sat unused for a long time on well water, a flush on your return is a good idea.

Commercial Tankless and When to Call Us

Restaurants, salons, offices and multi-unit buildings often use tankless systems, sometimes several units racked together with a shared control. That setup gives backup if one unit goes down and lets the system stage units on as demand climbs. Commercial installs need careful gas, venting and load planning. Our commercial plumbing service can review your building’s hot water demand before you commit.

Call us if your hot water keeps going lukewarm, the unit shows an error code you can’t clear, you smell gas or see water around the heater, or it’s been more than a year since the last flush. It also makes sense to call before your old tank fails, so a conversion can be planned instead of rushed.

We serve Fort Myers, Cape Coral, Naples, Bonita Springs, Lehigh Acres, Punta Gorda and Fort Myers Beach. See our full service areas, call (239) 518-4198, or send a request through our contact form.