A tankless heater that fires and produces hot water has proved almost nothing.
One tap running, a small demand, mild weather — most units will manage that even when something is meaningfully wrong. An undersized gas line, a partially restricted supply, a unit specified for a rise it can't actually deliver: none of those show up at low demand.
They show up the first time two showers run in January. Which is months after everyone has gone home.
The only test that means anything is the one that reproduces your actual worst case: more than one fixture running at once, temperature measured at the outlet rather than assumed, and held there long enough to prove the unit and the gas supply can both sustain it.
That takes twenty minutes at the end of the installation. It's the difference between an installation that's finished and one that's merely connected.
Tap the call button and tell us what you have now and how many fixtures get used together.
AllPro Plumbing Services sizes, installs, and services tankless water heaters across Prairie Village, KS for homes and businesses.
Seven checks. Firing up and feeling the water is not one of them.
With a thermometer, against the setpoint. Not judged by hand.
So the actual delivery is known rather than assumed.
Reproducing your realistic peak — because a unit that satisfies one tap and falters on two has told you nothing until you test the second.
A gas supply that's marginal delivers fine briefly and sags when the demand persists — which is precisely how an undersized line hides.
Static pressure proves nothing. The reading that matters is under load, with everything else in the property that draws gas accounted for.
With the termination checked and clearances confirmed.
Through the drain and any neutraliser.
Measured output, at that flow, at that incoming temperature — so you have a baseline. If performance drops in two years, you'll know by how much rather than wondering whether you're imagining it.
A tankless unit's gas input while running is far higher than a storage heater's, even though it runs for less time. The existing line frequently isn't sized for it.
An undersized line still delivers adequate pressure at rest, and adequate pressure briefly under load. The pressure drops as demand continues — and the unit responds by reducing output, which reads as lukewarm water rather than as a gas fault.
So it looks exactly like an undersized heater. People spend years assuming they bought too small a unit, when the unit is fine and the fuel isn't arriving.
Measure gas pressure at the unit while it runs at full input, with the meter capacity and everything else drawing gas accounted for.
And it has to happen at commissioning, because retrofitting a larger gas line through a finished property is real work — far better identified during the installation than diagnosed two winters later.
Click Here To Call Number(833) 435-3258Commissioning proves the specification. The specification has to be right first.
How much you want at once, cumulative across every fixture running simultaneously.
How far the water must be lifted — your output temperature minus what's arriving.
Any unit delivers high flow at a small rise, or modest flow at a large one. It cannot do both, and every headline rating is quoted at a rise that flatters it.
Colder incoming water means a bigger lift — a unit comfortably serving two showers in July may manage one and a half in January.
The specification has to survive your coldest day, not your average one — and commissioning should test against that case, or as close to it as the season allows, with the measured figures recorded so the winter result is predictable rather than a surprise.
Any quote pricing only the unit and labour is incomplete. Gas sizing, venting, condensate, electrical, treatment, and service valves are the difference between a competitive-looking number and the real one.
Line and meter capacity checked against the unit's full input. The item most likely to be underestimated, and the one commissioning exposes.
Tankless units need their own, correctly routed and terminated with proper clearances. Condensing models need appropriate material for acidic condensate.
Condensing units produce condensate needing a drain and frequently neutralisation.
Minor on gas units. On whole-house electric, potentially substantial — sometimes a service upgrade.
Scale is the primary enemy of a tankless heat exchanger.
Allowing the unit to be flushed and descaled without draining the system. Cheap now, expensive to retrofit.
Tankless suits properties where
Good fitA storage tank may still win where
Think againThe long service life is what justifies the installation. It's conditional.
Water passes through a narrow heat exchanger at high temperature. Minerals precipitate onto those surfaces, and even a thin layer insulates the exchanger, reduces output, and forces the unit to work harder.
Annually as a baseline, more in hard water or heavy commercial use.
A descaling solution circulated via the service valves — which is why those valves belong in the original installation.
Output drops gradually enough that people adjust. Then error codes. Then the exchanger fails.
A measured baseline means a later drop in output is provable rather than a matter of opinion — and distinguishable from a gas supply problem or a scaling one.
Multiple fixtures, measured temperature, held long enough to prove the gas supply sustains it — not one tap and a hand under the water.
Static pressure proves nothing. An undersized line delivers fine briefly and sags under sustained demand, which reads as a heater problem for years.
Temperature at the outlet with a thermometer, flow measured, and the figures written down.
So a drop in performance in two years is provable rather than debatable.
Descaling is what delivers the service life you're paying for.
If yours has never delivered what it should, that's frequently gas supply or commissioning rather than the heater — and it's a far cheaper finding than a replacement.
Licensed, insured, and background-checked plumbers serving Prairie Village, KS.
You'll have the sizing calculation and a fully itemised quote before anything is ordered.
AllPro Plumbing Services proudly serves Prairie Village, KS and the surrounding neighborhoods, sizing, installing, and servicing tankless water heaters for domestic and commercial properties throughout the area. Unsure whether you're in range? Call and ask.
Click Here To Call Number(833) 435-3258Running more than one fixture at once, measuring the output temperature with a thermometer rather than judging it, holding it long enough to prove the gas supply sustains it, and checking gas pressure at the unit while it runs at full input. Firing up on one tap proves almost nothing.
Because an undersized line delivers adequate pressure at rest and briefly under load, then sags as demand continues. The unit responds by reducing output — which reads as lukewarm water and gets blamed on the heater. Static pressure would look perfectly fine.
Possibly, but check the gas supply first. An undersized line behaves exactly like an undersized unit, and it's far more common than people assume. It's a measurement, not a guess, and it's worth doing before replacing anything.
Colder incoming water means a bigger lift, and flow trades against temperature rise. The same unit serving two showers in summer may manage one and a half in mid-winter. Sizing must use your coldest case, and commissioning figures let you predict it.
It means it won't run out — but only at the rate it delivers. Exceed that with too many fixtures at once and the temperature drops rather than the supply stopping.
Because they're a baseline. If output seems to drop in two years, measured numbers make it provable rather than a matter of opinion — and they help distinguish scaling from a gas supply problem.
Because a tankless heater is rarely a straight swap. Gas lines frequently need upsizing, venting differs entirely, condensing units need condensate drainage, and hard water needs treatment. That's the gap in most cheap quotes.
Yes, and it's worth doing where a unit has never performed as expected. Gas pressure under load, measured output at the fixtures, and combustion checks frequently identify the problem — and it's a much cheaper finding than a replacement.
Isolation valves letting the unit be flushed and descaled without draining the system. Cheap at installation, expensive to retrofit — and descaling determines how long the unit lasts.
Annually as a baseline, more often in hard water or heavy commercial use. Scale on the heat exchanger reduces output, triggers error codes, and eventually destroys the most expensive component.
For a single fixture, comfortably. For a whole house, it requires substantial electrical service, and the upgrade sometimes costs more than the heater.
Not necessarily. A sound storage heater with years left isn't automatically worth replacing. When it's near the end of its life is the natural moment.
Any unit will fire on one tap in mild weather. The faults that matter — an undersized gas line, a marginal supply, a specification that can't meet your winter rise — all hide at low demand and surface months later, when two showers run on a cold morning and nobody is there to see it.
AllPro Plumbing Services commissions under real simultaneous load, measures output with a thermometer rather than judging it, checks gas pressure while the unit runs at full input, and leaves you the figures as a baseline.
Tap the call button and tell us what you have now — and how many fixtures get used together.
Click Here To Call Number(833) 435-3258