Tankless water heaters are good equipment. They're also the plumbing product with the widest gap between what buyers expect and what they actually do — and almost every disappointed owner was disappointed by an expectation rather than by the unit.
Two sentences prevent most of it.
Endless is not instant. A tankless unit will produce hot water for as long as you want it. It will not produce it any faster at the tap than a tank did.
Unlimited duration is not unlimited flow. It never runs out. It absolutely can run short — if you ask for more gallons per minute at once than it's rated to heat.
Everything else on this page follows from those two, and from a specification most buyers never see: how cold your water is when it arrives.
PrimeFlow Plumbing Services sizes and installs tankless systems across Jerome — for your actual water temperature, with the full scope quoted.
Tap to call, or read what the brochure doesn't say.
"I'll get hot water instantly."
No. Hot water still has to travel from the unit to the tap, and that pipe is full of cold water. If your shower took twenty seconds to run hot before, it will take about twenty seconds now — plus a moment for the unit to fire. Some people find the wait slightly longer than with a tank. The fix is recirculation, which is a separate system and a separate cost, covered below.
"I'll never run out of hot water."
True — for duration. Not true for simultaneous demand. A tankless unit heats water as it passes through, at a maximum rate. Ask for two showers and a dishwasher at once and you may exceed that rate, at which point the water gets cooler rather than running out. A tank behaves the opposite way: full flow until it's empty, then nothing.
"It'll work at any tap setting."
Not quite. Tankless units need a minimum flow rate before they fire. A very light trickle from a tap may not activate the unit at all, which is occasionally noticed at a bathroom basin used gently, or at a low-flow fixture.
"The temperature will be constant."
Mostly. The exception has a name — the cold water sandwich. If you turn the hot water off and back on shortly afterward, the still-hot water sitting in the pipe arrives first, followed by a slug of cold that passed through before the unit re-fired, then hot again. It's most noticeable with fixtures that cycle, and modern units with buffer tanks reduce it considerably.
"There's no maintenance."
There is, and it matters more than with a tank. Tankless units need periodic descaling, particularly in hard water areas, because scale builds on the heat exchanger and directly degrades performance. Many manufacturers make regular servicing a condition of warranty coverage. Skipping it is the most common reason a tankless unit disappoints its second owner.
None of this is an argument against tankless. It's an argument against buying one on the strength of a phrase like "endless hot water" without knowing what it means.
This is the single most important number in tankless sizing, and it's the one that gets left out of comparisons.
A tankless unit doesn't have one flow rating. It has a flow rating at a given temperature rise — how many degrees it has to lift the incoming water to reach your target.
The arithmetic is simple. If your water arrives at 70°F and you want 120°F at the tap, that's a 50-degree rise. If it arrives at 40°F in winter, that's an 80-degree rise. The same unit delivers considerably fewer gallons per minute at 80 degrees than at 50.
Which means the rated flow on the box is close to meaningless in isolation. A unit advertised at a high GPM figure is quoting it at a modest rise — often one that doesn't apply anywhere with a cold winter.
Incoming water temperature is seasonal and regional. The same house that has abundant hot water in August can find two showers a struggle in February, and nothing has failed. The unit is doing more work per gallon.
So sizing has to be done at your winter incoming temperature, not an annual average and not a manufacturer's headline. A system sized on summer numbers works beautifully for most of the year and disappoints for exactly the months you care about.
We size for winter. It's the whole point of doing the calculation.
Once you know the rise, the second half is simultaneous demand.
Gas tankless is the common residential choice, and it brings three requirements that frequently dominate the installation cost.
Electric tankless avoids venting and gas entirely — and substitutes a serious electrical requirement. Heating water instantaneously with electricity takes a great deal of current, frequently multiple dedicated high-amperage circuits and, in many homes, a service upgrade. In colder regions where the temperature rise is large, whole-house electric tankless is often impractical for that reason. It works well for point-of-use applications — a remote sink, a workshop, a garage — where demand is small and the run from the main heater is long.
We'll tell you early if the answer is that your property can't reasonably support the option you're considering. It's better information at the enquiry stage than after equipment has been ordered.
Swapping a tank for a tankless unit is rarely a like-for-like exchange, and this is where quotes diverge.
Ask any bidder which of those are in their number. The gap between quotes on this job is almost always one of these items, not the appliance.
If your real complaint is waiting for hot water, tankless alone won't solve it — recirculation will.
Scale is the primary enemy of a tankless heat exchanger.
We install both, so this is a genuine comparison rather than a sales position.
Tankless suits you if you want unlimited duration, you value the space saved, the household's simultaneous demand is understood and matched, your gas supply and venting can support it, and you'll actually maintain it.
A tank remains the better answer if the gas or electrical upgrade cost is disproportionate to the benefit, if your demand is heavily simultaneous but short, if you're replacing urgently and cost matters most, if the property is a rental where descaling won't reliably happen, or if you're in a cold-incoming-water region where the required tankless capacity gets expensive.
A hybrid or heat pump water heater is a third option worth knowing exists — efficient, tank-based, with its own space, temperature, and noise considerations.
We'll give you the numbers for the realistic options and the reasoning. What we won't do is quote a tankless installation without mentioning that the gas line upgrade is half of it.
We install and service tankless systems for restaurants, cafés, salons, gyms, and multi-unit residential buildings across Jerome.
Commercial demand profiles are peaky — a restaurant's hot water requirement clusters around service, not across the day, which suits tankless in some applications and defeats it in others.
Manifolded multiple units are common commercially, allowing capacity to be staged and one unit to be serviced without shutting off hot water entirely.
Some equipment and settings have specified hot water requirements, which makes reliability and recovery a compliance matter rather than a comfort one.
Scale is a bigger problem commercially, because throughput is higher. Scheduled descaling is the difference between equipment that lasts and equipment that fails during service.
You'll get one written quote covering all of it.
PrimeFlow Plumbing Services proudly serves Jerome, ID and the surrounding neighborhoods, installing and servicing tankless water heaters in residential and commercial properties throughout the area. Unsure whether you're in range? Call and ask.
No. Hot water still has to travel the pipe to the tap, so the wait is roughly what it was. If the wait is your real complaint, recirculation is the answer — and it's a separate system.
Not by duration, but yes by flow. If simultaneous demand exceeds what the unit can heat at your temperature rise, the water gets cooler rather than stopping.
It's how many degrees the unit must lift your incoming water to reach your target. The colder your supply, the fewer gallons per minute a given unit can deliver — which is why sizing must use winter figures.
Because the box quotes a modest temperature rise. At a realistic winter rise, the same unit delivers meaningfully less.
A short slug of cold water arriving mid-use when hot water is turned off and back on shortly afterward. Modern units with buffer tanks reduce it considerably.
Yes — periodic descaling, typically annually and more often in hard water. Many warranties require documented servicing, and skipping it is the main cause of disappointing performance.
Frequently, yes. Tankless units demand far more gas than tanks, and existing pipework is often undersized. It's the most common significant item in a conversion quote.
For point-of-use applications, readily. For a whole house, the electrical requirement is substantial and often means a service upgrade — particularly where incoming water is cold.
Generally not. Gas units need electricity for controls and the fan, so an outage means no hot water unless there's backup power.
Typically longer than a tank when maintained, which is a meaningful part of the economic case — and conditional on the descaling actually happening.
It depends on your demand pattern, your gas and venting situation, and whether the upgrade costs are proportionate. We'll give you the numbers for both and the reasoning.
Yes. Installation involves gas, venting, and often electrical work, all of which are permitted and inspected. We handle it.
The unit is often the smaller part. Gas line resizing, venting, condensate, and electrical work dominate the number, and you'll get all of it in one written quote.