hot water heaters installed in parallel Guide to Alternative Hot Water Sources
how to choose among different ways to make domestic hot water

  • ALTERNATIVE HOT WATER SOURCES - CONTENTS: Description of Types of Alternative Hot Water Heating Methods: electric, gas, high efficiency gas, oil, high efficiency oil, solar, tankless coils, instantaneous water heaters, point of use water heaters and other Alternative Hot Water Sources & Methods
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This article describes alternative methods of providing domestic hot water, comparing the characteristics of various hot water heating methods and describing different ways to heat water for washing and bathing.

Whether you make your building hot water using a water heater, geyser, or hot water cylinder, there are alternative methods that can dramatically change the hot water quantity, pressure, flow rate, and operating cost.

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A Comparison of Alternative Hot Water Heaters & Sources

High efficiency gas fired water heater schematicThanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.

There are easy steps one can take to determine why the hot water pressure or quantity in a building are inadequate. We discussed tankless coils for making hot water, anti scald valves, and the problem of clogged hot water piping or clogged tankless coils. Then we discussed steps to increase hot water quantity such as insulating water piping and water tanks, and the use of extra tanks to pre-warm or store hot water.

Before you start fixing or buying stuff to fix a hot water problem hot water problems and diagnostic guides for all kinds of hot water troubles are summarized
at WATER HEATER PROBLEM DIAGNOSIS. You might want to check there to be sure you're fixing the right problem.

Below we describe some alternative ways to make hot water, either to replace or to supplement an existing hot water supply system. After knowing what the hot water problem really is, there are steps we can take to get more hot water or to increase hot water pressure.

Ways to improve total hot water quantity, pressure, temperature and flow are discussed beginning
and continuing
at HOT WATER QUANTITY IMPROVEMENT. Here we provide links to articles describing alternative methods for obtaining hot water or for obtaining improved quantity of hot water at buildings.

The following articles discuss alternative ways to produce domestic hot water for washing and bathing.

The characteristics of various water heaters such as life expectancy, cost, safety, and capacity are discussed at

Scale, mineral deposits, lime reduce hot water quantity: because scale, mineral deposits, lime, and silt in any water heater, and certainly scale on electric water heating elements can reduce the amount of hot water available as well as slowing water heater recovery time, see WATER HEATER NOISE DIAGNOSIS, CURE where we describe deliming and scaling in water heaters.

Multiple Hot Water Sources? How to Use Separate Oil, Gas, or Electric, Solar, Wind, or Combination-fuel Water Heaters for More Hot Water

Separate water heaters can provide more hot water than a tankless coil in most cases and choices among water heater types by fuel, size, recovery rate, etc. can make a big difference in the hot water quantity, pressure, flow, and cost at a building. This article explains some alternative water heating methods.

Use Instantaneous Water Heaters for Increased Hot Water Supply

Instantaneous water heater sketchInstalling an instantaneous water heaters are usually installed as a 'point-of-use' hot water system. You can see the basic appearance of a point-of-use instantaneous water heater in the sketch at left, provided courtesy of Carson Dunlop Associates.

For example an instantaneous water heater, electric or gas fired, may be installed at a single kitchen or bathroom.

In the U.S. and Canada, this is an approach to providing hot water that is usually applied where the total hot water delivery rate needed is modest or where only a limited number of fixtures need to be supplied with hot water.

Higher-capacity instantaneous water heaters are available, and in countries where people use water more modestly, these systems are sometimes installed as the only hot water supply.



How to connect multiple water heaters in parallel to increase total hot water quantity

hot water heaters installed in parallelWhere hot water volume requirements are high, in addition to installing a single larger-capacity water heater, one can install a several water heaters connected in parallel. You can see this design in our sketch at left, provided courtesy of Carson Dunlop Associates.

Parallel water heaters means that all of them are "on" and heating water at the same time, providing a very large quantity of hot water to the building.

We see this installation most often when building occupants find that they do not have enough hot water but their present water heater is in good condition.

Rather than scrapping a perfectly good water heater to install a single larger unit, a second water heater is simply added, installed in parallel to the first one.



How to increase hot water quantity using multiple water heaters in series for lower hot water cost

Some buildings use water heaters installed in series to handle variations in hot water demand more economically. Unlike the illustration of parallel water heaters shown above, water heaters connected in series means that incoming cold water flows first into heater #1, then out of heater #1 into heater #2, then out of heater #2 into the building hot water supply piping (or into additional water heaters if more than two are used.)

A synonym for water heaters connected in series is a cascaded water heater design. Cascaded or in-series water heaters is an economical way to handle large variations in hot water demand in a building.

See EXTRA TANKS to INCREASE HOT WATER for more discussion of extra tanks to provide more hot water.

Use of a Side Arm Coil to Make Hot Water from a Heating Boiler

Side arm coil for hot waterAs the sketch at left shows (courtesy of Carson Dunlop), a side arm coil is a variation on the tankless coil (inside the boiler) discussed at TANKLESS COILS where we explain how these work and what goes wrong, and further at Tankless Coil for Hot Water where we describe how to get more hot water from a tankless coil.

A side arm coil is quite similar to an in-boiler tankless coil except that it is located outside of the the heating boiler itself.

We found this system common on older home heating systems such as those using a GE down-fire heating boiler or other boilers whose original design did not include an opening and fittings to mount the tankless coil right into the boiler itself.

Also see WATER SOFTENERS & CONDITIONERS - how to install and adjust a water softener to avoid hot water piping or tankless coil clogging due to hard water and minerals - since a side arm coil can also become clogged by the minerals in hard water.


Continue reading at HOT WATER EFFICIENCY IMPROVEMENT or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Or see these

Hot Water Quantity & Flow Improvement Articles

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ALTERNATIVE HOT WATER SOURCES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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