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Hot Water Conservation

/Hot Water Conservation
Hot Water Conservation 2018-08-13T14:24:38+00:00

Except for your heating system, your water heater consumes more energy than any other appliance in the house, even if it’s a tankless water heater, gas or electric.


Through the use of water heater and pipe insulation, modifying plumbing layouts, and using tankless water heaters where appropriate, most hot water plumbing systems can be made more efficient saving money and water.

Human Behavior – Critical to Energy and Water Conservation

For the most part it is humans, not machines that waste energy and water.  The energy savings from even the most efficient appliance can be easily lost by not operating it efficiently.  Hot water conservation has to be part of the users behavior.

For instance, the newest washing machines are very efficient, and use much less water and energy than older models, but if you wash a small load but set the washer for a large load with a hot wash and a warm rinse when the clothes would have been just as clean if you had set the load to small and used a cold wash and cold rinse cycle.

The same goes for your dryer, dishwasher, and even your air conditioning system. I’ve know people to turn up the air conditioner and yet leave doors and windows open because they like fresh air but it’s hot outside.  So much for that high-efficiency air conditioning system.

Saving Water – Change Your Behavior

Saving water and energy takes more than just efficient appliances, it takes human effort as well. Be aware of your habits and change them if need be.  Small adjustments to your usage habits can reap very large rewards. Stop letting the water run while you brush your teeth, only run the dishwasher with full loads, and things like that.

One study showed that about 80% of the time that hot water is used in the bathroom it never makes it to the fixture.  We have probably all been guilty of turning on the hot water faucet to wash our hands, but we are too impatient to wait for the water to get hot, so we just wash our hands in cold water, and as we finish, the water is just starting to get warm.

All we succeeded in doing was filling the hot water piping with hot water which will cool off… a near total waste of water heating energy.  Single handle faucets are another area of waste.  How often do you swing the handle all the way to the right to fill a glass of water?  If you don’t you are drawing some hot water into the hot water pipe, which again will just cool off without providing any useful benefit.

Plumbing Layout Can Make a Difference

Cold water piping doesn’t really influence water or energy consumption. The cold water plumbing might as well be just a storage tank. When you want some cold water you just turn on the tap and take it.  The hot water plumbing is a whole different story though.

On the hot water side, the longer the pipe the more the energy and water gets wasted. When the user wants hot water he must purge the cooled off hot water out of the piping, normally running it down the drain. This of course, is a waste of water.

As hot water travels through the pipe, it looses energy to the piping material and to the area around the pipe, resulting in wasted energy. These loses can be minimized by covering the hot water piping with pipe insulation, and by making the piping runs as short as possible.

Water Heaters

When purchasing a new water heater be sure to do a little research and select a model that is energy efficient. Use the Energy Guide Label that comes affixed to all new water heaters. The label will help you compare the energy use and cost of deferent models.

The information on the label is derived from standard testing procedures established by the U.S. Department of Energy. A bar scale offers the range of operating costs for similar models so you can see how the deferent models compare. Also, a yearly cost table allows you to estimate the cost of operation at your local rate.

Electric Tankless Water Heaters

Electric tankless hot water heaters can save you energy since they do not have the standby losses that a conventional tank type storage water heater has.  However, electric tankless water heaters require a lot of electricity to be able to heat the water rapidly as is needed with a tankless unit.  Be prepared to install extra heavy electrical wiring and dedicated circuit breakers in all but the smallest units.

In many cases the electric tankless units are ideal for point-of-use installations where the heater is located adjacent or very close to the fixture or fixtures it will be supplying. By locating the heater close to the end use fixtures, the losses associated with purging the cooled off water and the loss in temperature as the water flows through the pipe are eliminated or greatly reduced. More information about electric tankless water heaters.

Gas Tankless Water Heaters

Tankless water heaters that use gas are more efficient than storage heaters because as with the electric units, they don’t have the stand by losses associated with storage water heaters.  The larger models that are suitable for whole-house applications will usually require larger gas supply lines than a standard tank type heater, and larger venting. More information about gas tankless water heaters

Tankless Water Heater Savings

Although you will benefit from endless hot water and lower energy consumption, you will also have to consider the cost of the heater itself and the installation. The cost verses savings must be taken into account if you want to save money as well as energy.

The savings in dollars from the elimination of stand-by losses in tankless water heaters is not large, usually less than $10.00 a month, so paying thousands of dollars extra may not be cost efficient. If you can get a tax break from the federal government it will generally result in a monetary savings since it brings down the installed cost substantially.

Tankless Water Heater Problem: Slow Hot Water

Tankless water heaters typically require a longer wait for hot water to arrive at your fixture. This is because there is no hot water waiting for you to open the faucet. With the tankless units when you open the faucet the water heater turns on, and begins heating the water. However, it takes time to heat water, and so you won’t get full hot water temperature out of the outlet and headed in your direction until the water has passed completely through the heat exchangers.

Slow Hot Water

A study done on tankless water heaters by the Australian government found that the wait for hot water with a tankless water heater was typically 10 to 20 seconds longer than with a storage type heater.

The end result of slow hot water is the wasting of more water running it down the drain while you wait.  Low flow fixtures add to the wait, but they don’t really increase the amount of wastage… it’s just an inconvenience.

There are ways of mitigating the slow hot water problem, usually involving recirculation pumps, but those typically won’t work with tankless water heaters. But there are some hot water delivery systems that do address the slow hot water problem. More aboutslow hot water

Hot Water Demand Systems

Hot water demand pumps or systems pump the hot water to your fixture at high speed without running water down the drain. They do this by circulating the hot water through the pipes in a loop back to the water heater.  Unlike a conventional recirc pump, they shut off as soon as they detect hot water at the pump.  They can use either a dedicated return line or the cold water line to complete the loop back to the water heater. The pump is usually located under the furthest fixture from the water heater.

Demand hot water systems do work with tankless water heaters. You must get one sized big enough to turn on the heater though…typically 1/2 to 3/4 gallons per minute.

By combining a tankless water heater and a hot water demand pump you save both energy and water making your hot water plumbing considerably greener.

Hot Water Recirculating Systems Are Not Demand Systems

Beware, there are a number of hot water circulating systems often referred to as “Recirc Pumps”, “Circulating Pumps”, “Recirculating pumps” etc., and these are not demand hot water systems.  A demand hot water pump requires that you push a button that starts the pump.

If the pump starts and stops based on a timer or based on temperature it is not a demand system.  Few hot water recirculation systems are powerful enough to turn on a tankless water heater. Most tankless water heater models are not compatible with hot water circulating systems. All tankless heaters are compatible with demand hot water systems.

Metlund D’Mand Systems, RedyTemp, and Chilipeppers

ACT Metlund manufactures 3 models of D’mand Systems… The S-50T, the S-70T, and the S-02T.

RedyTemp manufactures several models of hot water circulating systems and some or all can be used in a “demand” mode of operation.

Chilipepper Sales manufactures a hot water demand system that works with any and all models of tankless water heaters.

For a comparison of the Metlund D’mand System and the Chilipepper: Metlund D’Mand Vs Chilipepper

Hot Water Leaks – Stop them

Leaky hot water faucets waste both water and energy. A dripping hot water fixture that can  fill a cup in 10 minutes will waste over 3,000 gallons of hot water in a year.

Another common source of hot water leaks is the Pressure Temperature Relief Valve. The relief valve which is located on your water heater tank (typically tankless water heaters do not have a relief valve, but some do) can develop leaks, and since the leak is often piped to another location you don’t even know it’s leaking.

If the valve is leaking try to flush it out by lifting the lever attached to the valve. This can sometimes clear out any foreign matter obstructing the full closing of the valve.

Saving Water and Energy in Your Home is Not Difficult!

Saving the maximum water and energy with your hot water plumbing system means doing several things which may include the following items:

  • Modifying your behavior if applicable
  • Changing your plumbing layout if possible
  • Insulating your hot water pipes where accessible
  • Installing a tankless water heater where appropriate
  • Use a hot water demand pump if you have long pipe runs
  • Find and repair any hot water leaks

Completing those tasks will ensure that your are saving the most water and energy possible and doing your part to reduce your carbon footprint through efficiency.

Reducing your household’s demand for hot water simply means using fewer gallons of hot water. This can be achieved in three ways: 1) changing a few of your habits; 2) reducing the water flow in your plumbing system; and 3) increasing the efficiency of your hot water system.

Reducing Water Flow
The easiest way to reduce consumption is to reduce water flow. There are two ways to do this:

Add low-flow faucet aerators to existing fixtures, or

Install new energy-efficient fixtures.

Older showerheads use five to eight gallons of water per minute. Watersaving showerheads use two to three gallons per minute. At a cost of $10 to $40, the payback in energy savings is one to three years.

Faucet aerators at bathroom, utility room, and kitchen sinks can reduce water flow somewhat, but a changeover to low-flow aerators can reduce flow to a more effective and usable level (two gallons per minute).

If you have unusually high water pressure in your home, you may want to install a pressure reducing valve that can slow the flow rate of water 20-50 percent. The valves themselves cost about $50-$60. Having a plumber install one will cost $50-$100. Reduced pressure, in addition to saving water, can help reduce an existing water hammer problem in your plumbing.

Buying a New Water Heater
Water heaters have an estimated life of 10-12 years. After that time, most water heaters develop leaks from corrosion and need to be replaced. When it’s time to replace your old water heater:

Buy an Energy-Efficient Heater
They cost somewhat more to purchase than conventional water heaters, but the savings in reduced heat loss can offset this in two to four years.

Use the Energy Guide Label
Affixed to all new water heaters, it helps you compare the energy use and cost of deferent models. The information on the label is derived from standard testing procedures established by the U.S. Department of Energy. A bar scale offers the range of operating costs for similar models so you can see how the deferent models compare. Also, a yearly cost table allows you to estimate the cost of operation at your local rate.

Your Habits Can Reduce Demand

Shower Vs Bath
A bath generally uses more hot water than a shower. A bath takes 15-25 gallons of hot water whereas a shower takes 10-15 gallons. You can compare the amount of water used in a shower to that of a bath by closing the drain before showering. If your tub is less full after a shower than it would have been after a bath, then you know you can save hot water by showering. If it’s just as full, or even fuller, you may want to stick to baths or take shorter showers. When showering, turning off the water while soaping up is an effective way to reduce consumption.

Cold Water Wash – Laundry
The clothes washer is second only to bathing in consumption of hot water. A standard size clothes washer uses about 25 gallons of hot water when operated in hot wash/warm rinse mode. A large capacity washer can use as much as 40 gallons of hot water.

One approach to reducing demand is to use a warm wash/cold rinse setting on your washing machine. This can save about 65 percent of the energy you would use with a hot wash/warm rinse. You should note that perspiration and oily stains can be difficult to remove from synthetic fabrics without hot water. Also, in addition to cleaning, hot water helps destroy bacteria.

Using cold water only for washing can be appropriate for some loads. This setting offers the greatest savings since no hot water is used. It is important to use a suitable cold water or liquid detergent for best results.

When shopping for a new washing machine, look for an energy-efficient, low water volume model.

Washing Dishes
Automatic dishwashers use about 10-15 gallons per load. Washing dishes by hand may use less or more than this depending on how careful you we. Newer, efficient dishwashers use as little as 5 gallons per load, so it pays to shop. To conserve energy, only use the dishwasher when it’s fully loaded, and use the air-dry cycle. The dishes will dry from the heat of the washer. Don’t pre-rinse dishes just scrape clean and load.

Conserve Water When Using Your Washing Machine
Wash clothes in cold water when you can, or use the cold setting during the rinse cycle.

Use the lowest water level setting for the amount of clothes you are washing.

Hot Water Heater
Adding a blanket to your hot water tank is an easy do-it-yourself job that can save you money on water-heating bills. Be careful not to insulate too close to intake or exhaust vents on gas water heaters.

Increasing Water Heating Efficiency

In addition to reducing the demand for hot water, there are a number of measures you can take to improve the efficiency of your hot water system.

Set Back the Water Heater Thermostat
The state of Washington now requires that all new water heaters be set at 120 degrees F at the time of sale. This increases the safety and energy efficiency of the heater.

If your water heater was purchased prior to 1984, however, it’s likely that the thermostat is set higher than this, probably between 140 degrees F and 150 degrees F. You should set it back if this is the case. Most people shower at a temperature of 105 degrees F, so a setting of 120 degrees F will still require mixing with cold water for a comfortable temperature.

Hot water temperatures greater than 120 degrees F are not necessary and should be reduced for several reasons:

It can cause scalding. Children and seniors are most often scalded. Scalding occurs in: 2 seconds at 150 degrees F, 30 seconds at 130 degrees F, 15 seconds at 140 degrees F, 10 minutes at 120 degrees F

It causes the water heater to lose heat at a much greater rate than would occur if the temperature was kept lower; and

It increases the rate of corrosion on internal fittings and other surfaces.

By setting back the thermostat to 120 degrees F (down from 150 degrees F), energy demand is reduced by 15 percent.

You can reduce energy demand and increase safety by setting back the thermostat on your hot water heater to 120 degrees F. (If your water heater was purchased before 1984, It’s likely that the thermostat was set higher than 120 degrees F.)

Insulate Your Water Heater
Older water heaters lose heat quickly because they contain only an inch or two of fiberglass insulation (R-5). To reduce heat loss, they should be wrapped with an additional fiberglass insulation.

Insulating kits can be purchased at home supply and hardware stores, and some electric utilities will install them at no charge for customers. Most have an insulating value of R-11 and will save $20-$28 per year at current rates.

Rigid foam board insulation placed under the water heater can further reduce heat loss. About two inches of extruded polystyrene board is recommended since it resists compression and does not absorb water.

Gas water heaters should be wrapped with insulation specifically made for gas water heaters. These kits are designed so that they won’t block the air intake and insulation will not come in contact with the flue. This is essential for proper functioning of the heater and to avoid a fire hazard.

Insulate Pipes
Your house is a good candidate for pipe insulation if you use water frequently throughout the day, if the pipe runs are long, or if they pass through an insulated crawlspace or basement. It is necessary to wrap hot water pipes only. Pipe insulation comes in different forms:

Closed-cell flexible foam tubes (R-3 to R-5);

Rigid foam (R-7); and

Fiberglass batts (R-11).

Other Water Heating Alternatives
If you have already taken basic hot water conservation measures, and seek further reductions of your hot water bill, other water heating alternatives may be considered. These include tempering tanks and demand water, heat pump, solar, and wood-fired water heaters. In general, these systems are most cost-effective in new homes or for families using greater than average quantities of hot water.

Anti Convection Valves
If the hot and cold water outlet and inlet run vertically up from the water tank convection up these pipes causes heat loss when the tank is not being used. To reduce heat loss, anti convection valves, essentially tiny ball check valves, can be purchased at plumbing outlets and installed on both the inlet and outlet of the water heater. You may need a plumber to install them for you. If so, wait until other plumbing work needs to be done. This will save on costs.

Water Heater Timers
Timers are not very effective at reducing energy use unless time of use (or “peak”) rate structures are in use. Washington does not have these rate structures. Also, if the tank is well insulated, the savings from timers would be relatively small.

A water heater timer might save 36 kWh (or $1-$2) per year on a well insulated water heater. Tank insulation wraps, because they are simpler, less expensive and more effective, are a preferable means of saving energy.