Guide to Alternative Hot Water Sources
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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
How to use multiple water heaters in series for more hot water and lower hot water cost
Guide to range boilers & guide to side arm coil water heaters
Solar water heater suggestions to save on water heating cost
Questions & answers about alternative ways to make domestic hot water

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.

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A Comparison of Alternative Hot Water Heaters & Sources

Thanks 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 at HOT WATER IMPROVEMENTS 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.

Electric water heaters: if you have no hot water or insufficient hot water, check that the electric water heater power is on - check the water heater switch as well as other fuses or circuit breakers that control the heater. If the water heater has power, check that the water heater electrodes have not been damaged. Finally, check the water heater and its heating elements for scale deposits.
High Efficiency Water Heaters such as direct-vent gas-fired water heaters
Indirect-fired Water Heaters which use a separate heating boiler to produce a larger quantity of hot water
Instantaneous Water Heaters point of use systems that have little or no standby energy losses
Multiple water heaters in parallel to increase total hot water quantity
Multiple water heaters in series to stage hot water heating for varying levels of demand
Range Boiler Water Heaters an older form of indirect-fired hot water heating used with separate heating boilers
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 NOISES where we describe de liming and scaling in water heaters.
Side Arm Coil Water Heaters similar to instantaneous and tankless coil water heaters, often used with range boilers
Solar Water Heaters using solar collectors, an indoor water tank, pump and controls, using minimal "on-grid" energy
Tankless Coil Hot Water Increase a heat exchanging coil immersed inside of a heating boiler heats provides (somewhat limited) hot water. various tricks can significantly improve the safety and water quantity available
Tankless Water Heaters for instant hot water

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

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 NOISES 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

Installing 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.

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

Where 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.

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.

When the anticipated hot water demand is low, only water heater #2 may be running.
When the anticipated hot water demand is high, water heater #1 is turned on as well, doubling the volume of hot water available (if the heaters are of the same capacity in gallons or liters).
Water heater controls can be adjusted so that the "upstream" water heater, (water heater #1 in our example), is left turned off or perhaps set to a very low temperature. In either of these cases, the upstream water heater or tank functions as a "booster water warmer" reducing the energy use by water heater #2 by pre-warming water entering the active heater#2.

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

As 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.

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HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE LOSS

HOT WATER QUANTITY IMPROVEMENT
  Alternative Hot Water Sources & Methods
  Anti-Scald Valves & Hot Water Quantity
  CLOGGED PIPING & Hot Water Flow
  Extra Tanks to Increase Hot Water
  Insulate Hot Water Piping
  Insulate Hot Water Tank?
  Larger Diameter Water Supply Piping
  Water pipe clog diagnosis
  Water pipe clog repair guide

ALTERNATIVE HOT WATER SOURCES
  Electric Shower Heaters
  High Efficiency Water Heaters
  Indirect-fired Water Heaters
  Instantaneous Water Heaters
  Multiple water heaters in parallel
  Multiple water heaters in series
  Range Boiler Water Heaters
  Side Arm Coil Water Heaters
  Solar Water Heaters

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

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A Comparison of Alternative Hot Water Heaters & Sources

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

Use Instantaneous Water Heaters for Increased Hot Water Supply

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

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

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

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair