Typically a tankless water heater can provide 2 – 5 gallons (7.6 – 15.2 liters) of hot water per minute.
For example, a heater may be capable of increasing the temperature of incoming water 60 deg. F. at 3 gallons per minute flow rate.
The temperature rise that a tankless water heater can provide and the water flow rate that it can support depend on the heater's BTU output capacity which in turn is a function of the fuel used (gas-fired or electric) and the efficiency and the size of the heater.
Also see tankless water heater Problems & Defects where we describe the Tankless Water Heater Cold Water Sandwich Effect. Readers should also
see ALTERNATIVE HOT WATER SOURCES to distinguish among these types of hot water producing systems.
The original text of this article was provided courtesy of Carson Dunlop - that text has been edited and may not entirely reflect CD's views.
Our OPINION is that readers looking for plenty of hot water heated efficiently should also consider the heater we describe
at INDIRECT FIRED WATER HEATERS
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Comment: decide against the tankless system
(June 30, 2011) Don Wells said:
Your findings helped me to decide against the tankless system as it seems to be high maintenance. I'll stay with the gas water heater with a good insulation rating.
My opinion is that the life and performance as well as maintenance of tankless water heaters can be good depending on the local water chemistry. Hard water can be a problem for some units.
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 Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
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 HREF="http://www.consumerreports.org/">Consumer Reports offers an article on the efficiency versus the economy of tankless water heaters - see http://www.consumerreports.org/cro/Appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm
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