Catalog
Know-how
One question per page, answered with numbers.
When a whole-house electric tankless heater keeps up, by climate and fixtures, and what it asks of the electrical service.
VentingCondensate neutralizers for tankless water heatersWhat a condensate neutralizer does on a condensing tankless heater, how the media is refilled, and kits from the catalog.
GasCondensing vs non-condensing tankless water heatersHow condensing and non-condensing gas tankless heaters differ in efficiency, venting, condensate and flow per BTU, with examples from the catalog.
InstallDo you need an expansion tank with a tankless water heater?What a thermal expansion tank does, when a water heater installation needs one, and the sizes in the catalog.
GasDoes a tankless water heater need a bigger gas line?How much gas a tankless heater burns at full fire, why it often exceeds an old tank's line, and who sizes the pipe.
SizingElectric tankless water heater for a showerHow many kilowatts one shower takes from an electric tankless heater at different inlet temperatures, and the amps that means.
ElectricalElectric tankless water heater on 208 voltsWhat happens to a 240-volt tankless heater's power, flow and amps on 208-volt service, and why makers say to size up.
SizingGas tankless water heater for a family of fourWhat a four-person household usually runs at once, the flow that takes at a winter rise, and the gas units that cover it.
Buying guideGas vs electric tankless water heatersGas and electric tankless heaters compared on flow at a winter rise, installation (gas line and venting versus amps and breakers), and where each fits.
Buying guideHeat pump water heater vs tanklessHow a heat pump water heater and a tankless heater differ in efficiency, space, hot-water delivery and installation, and what changed for incentives after 2025.
MaintenanceHot water recirculation with a tankless heaterHow recirculation pumps cut the wait for hot water with a tankless heater, built-in versus add-on pumps, and the heater maker's rules.
SizingHow big a heat pump water heater do you need?Size a heat pump water heater by first-hour rating against your busiest hour, using AHRI's per-use gallons.
ElectricalHow many amps does an electric tankless water heater need?Amps for every common electric tankless size at 240 and 208 volts, how makers split the load across breakers, and what that means for a 200-amp panel.
MaintenanceHow to flush and descale a tankless water heaterThe flush most makers call for: isolation valves, a pump, a bucket of vinegar, how long it runs and how often, with Rinnai's published steps.
GasOutdoor tankless water heatersWhy outdoor tankless heaters need no vent pipe, where they go, and how freezing weather is handled.
Point of usePoint-of-use water heaters: when a mini tank beats a whole-house unitWhen a point-of-use mini tank or small tankless unit solves the wait for hot water at one fixture better than a bigger central heater.
GasPropane tankless water heatersHow to size a propane tankless heater, how many gallons of propane it burns an hour, and what to check on the tank and regulator.
Buying guideTankless vs tank water heaterTankless and tank water heaters compared on how they deliver hot water, sizing, space and installation, with how common each is.
SizingTankless water heater for a three-bathroom houseHow to size a tankless heater for a three-bathroom house: realistic simultaneous use, winter rise and the units that hold it.
InstallTankless water heater gas connectors and fittingsWhy a tankless heater's gas connector has to be sized for its input, the connection sizes on common units, and connectors in the catalog.
MaintenanceTankless water heater isolation valvesWhat a tankless service valve kit does, the connection types (threaded, sweat, push-fit) and the relief port, with kits from the catalog.
TroubleshootingTankless water heater minimum flow rateWhy a tankless heater needs a minimum flow to switch on, what Stiebel Eltron's chart shows, and fixes for a trickle that stays cold.
VentingTankless water heater venting explainedWhich tankless heaters vent in PVC, which need stainless, what a concentric termination is, and why the manual decides.
MaintenanceVinegar vs descaler for a tankless water heaterWhat makers say about flushing with white vinegar or a commercial descaler, how much you need and how long it circulates.
EfficiencyWhat is UEF on a water heater?What the Uniform Energy Factor measures, typical values for gas tankless, electric and heat pump water heaters, and the ENERGY STAR thresholds.
EfficiencyWhat is a first-hour rating?What the first-hour rating on a storage or heat pump water heater measures, where to find it and how to use it.
SizingWhat is a tankless water heater's temperature rise?What temperature rise means, how to find yours, and why every tankless flow figure is meaningless without it.
SizingWhat size tankless water heater do I need?Size a tankless water heater from the fixtures you run at once and your winter inlet water: the flow you need, the temperature rise, and the units that hold it.
InstallWho installs a tankless water heater?Which trades a tankless installation involves (plumbing, gas fitting, venting, electrical), why most homeowners hire them, and what to have ready.
TroubleshootingWhy your tankless water heater runs cold in winterWhy the same tankless heater runs fewer showers in January: colder inlet water, a bigger rise, and what to do about it.
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