Battelle finds water softeners aid energy efficiency, appliance life

Special to CONTRACTOR

COLUMBUS, OHIO — Water softeners extend the service life and maintain the energy efficiency of water heating equipment, showerheads and dishwashers, according to a study performed by Battelle Memorial Institute here. The study was performed for the Water Quality Association, Lisle, Ill.

Battelle reported that for gas storage and instantaneous water heaters, the use of a water softener to eliminate or minimize the scale forming compounds in water would result in the efficiency of the water heater remaining constant over the life of the unit. In contrast, gas storage and instantaneous water heaters using unsoftened water had a noticeable decrease in efficiency over the testing period resulting in higher natural gas use. This natural gas savings associated with the use of softened water will lead to direct energy and economic savings, the researchers said.

Electric storage water heaters did not record any difference in the electricity consumption between units receiving softened or unsoftened water, Battelle noted. The life of the heating element, however, on the electric water heater receiving unsoftened water would be expected to have a shorter life.

Low flow showerheads and faucets using unsoftened water clogged in less than seven days of accelerated life testing, whereas those units using softened water made it through the test without any problems, according to the research organization.

Battelle also noted that the dishwashers and clothes washers on either soft or unsoftened water made it through 30 days of accelerated scale testing, but the units on unsoftened water had noticeable scale buildup on all surfaces that had contact with unsoftened water.

The study tested devices fed with softened and unsoftened water under controlled laboratory conditions designed to accelerate the waterside scaling in the device and quantify the performance efficiency. The project specifically focused on efficiency improvements in household water heaters from use of softened water, and the subsequent effect on performance of fixtures, such as low-flow showerheads and faucets, and appliances, such as laundry washers and dishwashers.

For this study, Battelle tested 30 water heaters supplied by WQA over a 90-day period using a Battelle-developed and WQA approved test protocol. Battelle simultaneously studied the effect of water hardness on performance of faucets, low-flow showerheads, dishwashers, and laundry washers. Using the empirical data generated from the water heater testing and the effect on performance of fixtures and appliances, Battelle developed a differential carbon footprint assessment for homes using unsoftened water vs. softened water.

Battelle set up and tested 10 storage type gas water heaters, 10 storage type electric water heaters, and 10 instantaneous gas water heaters using an accelerated scaling methodology developed at Battelle.


The researchers tested 10 gas-fired 40-gal. water heaters with 38,000 Btuh burners; 10 electric 40-gal. water heaters using 4,500W heating elements; and 10 tankless gas water heaters with 199,000 Btuh burners.

Five of each type of device were tested without any preconditioning of the water supply, and the other five were tested using a water softener to remove hardness constituents from the water supply. Five units were chosen for each of the groupings in order to be able to calculate 95% confidence intervals for the results.

Battelle reported that the electric and gas storage water heaters and the instantaneous gas water heaters on soft water performed well throughout the entire testing period. In contrast, none of the electric or gas storage water heaters or the instantaneous gas water heaters on unsoftened water made it through the entire testing period because the outlet piping system consisting of ½-in. copper pipe, a needle valve and a solenoid valve became clogged with scale buildup. Although the pressure regulators and needle valves were tweaked throughout the testing to try to maintain constant testing conditions, all of the water heaters on unsoftened water were removed from the testing at some point due to the inability to maintain sufficient flow.

The instantaneous water heaters on unsoftened water had to be delimed at 1.6 years of equivalent field service, and the average efficiency of these units dropped from 80% at the start of the test to 72% when they were delimed. After deliming, the average efficiency of these units increased to about 77%.

The average efficiency of the gas storage water heaters on unsoftened water dropped from 70.4% at the start of the test to 67.4% at two years equivalent field service. These data were used to derive equations to predict the efficiency of gas storage water heaters as a function of water hardness and daily household hot water usage. The average rate of scale buildup in the gas storage water heaters on unsoftened water was about 528 gm/yr (1.16-lbs/yr). The average rate of scale buildup in the gas storage water heaters on soft water was about 7 gm/yr (0.01-lbs/yr).

The electric storage water heaters on both softened and unsoftened water were able to maintain a constant efficiency throughout the entire test period because the heating elements were completely submerged in the water, researchers said. However, researchers expect that the life of the heating element in unsoftened water would be shortened due to scale buildup increasing the operating temperature of the element. The average rate of scale buildup in the electric storage water heaters on unsoftened water was about 907 g/yr (2.00-lbs/yr). The average rate of scale buildup in the electric storage water heaters on soft water was about 14 g/yr (0.03-lbs/yr).

Ten low-flow showerheads were installed on the hot water supply coming from the instantaneous gas water heaters; five were tested on unsoftened water and five were tested using softened water. The low-flow showerheads on unsoftened water were removed from testing as they clogged up to the point of not allowing adjustment to a 1.25-GPM flow rate. All of the low-flow showerheads on softened water made it through the testing without any problems. However, the low-flow showerheads on unsoftened water clogged after an average of 3,203 gallons of water flow through them. At the end of testing, the low-flow showerheads were disassembled and the amount of scale buildup was documented with photographs of the components.

Ten low-flow faucets were also installed on the hot water supply coming from the instantaneous gas water heaters; five were tested on unsoftened water and five were tested using softened water. The low-flow faucets on unsoftened water were also removed from testing as they clogged up to the point of not allowing adjustment to a 1.25-GPM flow rate at any time during the test. All of the low-flow faucets on softened water made it through the testing without any problems. The low-flow faucets on unsoftened water clogged after the equivalent of 19 days of water flow through the faucets using an average of about 50-gal. of hot water per day, the researchers reported.

Six Kitchenaid dishwashers and General Electric laundry washers were purchased to test the effect of unsoftened water on the performance of the appliances. Battelle researchers controlled the wash and dry cycles of the dishwashers and the wash cycles of the laundry washers automatically, with the units going through eight cycles every 24 hours. The clothes washers were loaded with 7-lbs. of restaurant hand towels. The dishwashers were loaded with eight place settings of dishes and flatware. At the end of the 30 days of testing, the dishwashers and clothes washers were examined before a teardown analysis was initiated. The units using softened water were almost completely free of any water scale buildup. In contrast, the units using unsoftened water (26 grains per gallon) had noticeable water scale buildup on all of the interior surfaces.

To see the full report, click here (link opens as a pdf).

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