Water is a precious resource that we all must work to preserve. Taking steps to reduce evaporation conserves water in backyard pools by reducing how much water you need to add to "top off" a pool. One way you can do this is by recommending your customers add a liquid solar cover product to their pool maintenance program.

Despite the name, liquid solar covers do not heat the pool themselves. (Technically, they're classified as "evaporation suppressants.") They do, however, prevent the loss of heat from the vaporization of water. Simply put: When water evaporates, it requires energy in the form of heat for the process to occur. This process is the heat of vaporization. Energy is needed as water molecules begin to dance around and then dis-associate into a vapor gas. Evaporation suppression is the reduction of evaporation by controlling the rate at which vapor escapes from the water surface. In other words, the dance of the molecules is slowed down considerably. The use of a liquid solar cover works to save both heat and water reduction from evaporation. In addition, liquid solar covers help retain the heat of from the sun and thus keep pools warmer, longer.

Have you ever walked out to a pool to see water just steaming away? That's evaporation, and it occurs when a liquid becomes a gas or vapor. Water closest to the surface is constantly changing into water vapor. Four main factors contribute to evaporation:

1. The larger the surface area, the more water will evaporate. Thus, evaporation will be greater in pools with a large surface area.

2. Temperature: When the water temperature is higher than that of the surrounding air.

3. Air movement above the surface, such as windy conditions.

4. Relative humidity. The drier the air is the more evaporation occurs.

The strength of the radiation from the sun also plays a vital role in evaporation. In the Northern Hemisphere, evaporation rates are highest during the months of June, July and August. During dry summer months, evaporation rates increase. This is because water needs heat to reach the point of evaporation. It is possible for a 15,000-gallon pool to lose as much as 1,500 gallons a month during dry hot months. Liquid solar covers are ideal for these times in reducing water loss.

The Department of Energy states that 70 percent of total energy loss in a pool is due to evaporation.  According to the National Swimming Pool Foundation in the Pool and Spa Operator Handbook, 50 percent of relative heat loss is due to evaporation. When pools lose water to evaporation, continual top offs are needed. When water evaporates from a pool, only pure water leaves. Because of this, additional solids are left behind and both calcium hardness increases along with the total dissolved solids.

In some cases, the contents of source water can cost a pretty penny with the necessary adjustments needed due to metal or phosphate content from tap water. The balancing process has to be started again. This leads to additional labor time and the added expense of additional chemicals. Protecting pool water from evaporation is a cost-effective way to reduce unnecessary top-offs and water chemistry adjustments. Another benefit to the use of liquid solar covers is not only the savings in heat and water but also chemicals and precious time.

The traditional solution to heat loss and evaporation has been to use a solid cover, which does significantly decrease heat loss and evaporation. According to the U.S. Department of Energy, solid covers can prevent from 30 to 50 percent of water loss from the pool. Solar bubble covers are especially great at the beginning of the season to help the water heat up more quickly. There are, however, some downfalls to using a solar cover that you often don’t realize until you’re the one wrestling to put it back on by yourself: They are bulky and tough to move, not to mention the additional dirt and debris you may be introducing to the pool when dragging the cover through the yard.

If a bubble solar cover is left on too long on hot days, it may overheat the pool. This can consume chlorine quicker and could lead to green pools. Auto covers are available, yet can be prohibitively expensive. For these reasons, pool owners should consider using a liquid solar product to help maintain heat and reduce evaporation in their swimming pools. Liquid solar covers can also increase the length of the swimming season without the pool owners having to deal with any of the inconveniences of a solid cover. Liquid solar covers can help in savings of heat when pools are using a heater. According to the DOE report, it takes one BTU (British thermal unit) to raise 1 pound of water by 1 degree. However, each pound of 80 degree F water that evaporates takes 1,048 BTU’s of heat from the pool.

Liquid evaporation suppressants create an invisible liquid barrier at the surface of the swimming pool to help trap heat and reduce evaporation. This barrier is called a film. The film is very thin — only one molecule thick. Thus, the film is called a monomolecular film. The products are added to the skimmer with the circulation system running to disperse the monomolecular layer on the surface. Think of these products like putting a lid on a pot of boiling water.

Some pool pros are concerned about the formation of chloramines and the inability of oxidation gases to escape the pool due to the surface tension. It should be noted that the evaporation films are broken up when swimming or high winds or other means of breaking surface tension occur. At these times of surface tension, interruption such as heavy swimming provides plenty of opportunity for gases to escape to the atmosphere. In addition, there is some natural permeability of the films.

The purpose of liquid solar technology is to reduce heat loss and evaporation, and it works even when bathers are swimming in the pool. The monomolecular film creates extra surface tension on the water that prevents release of water vapor to the atmosphere. While the surface tension can be broken when swimmers are present, the tight molecular arrangement of the film causes it to quickly reform. The typical evaporation reduction rate of liquid covers runs from 15 to 40 percent. So, consider the 15,000-gallon pool that during the summer loses 1500 gallons a month…a liquid solar cover can save between 225 to 600 gallons of water a month. Over the three months of summer, that is a savings of between 675 to 1,800 gallons of water. The number one difference between a physical solar cover and a liquid product is that a physical cover does nothing if it is sitting bunched up in your backyard. If someone forgets to put the solid cover on and the temperature drops on a cool night, there will be considerable evaporation loss. Liquid solar products used along with a physical solar cover provides maximum coverage and extra protection.

Pool professionals are now realizing the importance of offering these relatively new products to their clients. Dick Abare from Algae Busters Pool Service in Tampa, Florida became a believer in the technology when he tried it on his own pool about five years ago. He was sitting poolside with his wife one evening watching a cloud of steam above their pool. “We could cook hot dogs with all the water and heat evaporating from the pool!” he said.

He took this opportunity to try out liquid solar blanket that he recently had been introduced to by an industry colleague. “I was amazed to see the pool go from steaming to a glass-like water surface,” says Abare. Ever since then, Abare has been successfully selling the liquid solar cover whenever he sells or repairs pool heaters. “When customers are investing a significant amount of money on a pool heater, I want to be sure they are satisfied with their purchase, because heating a pool can be expensive,” Abare says.

Terry Arko has more than 30 years of experience in the pool and spa/hot tub industry, working in service, repair, retail sales, chemical manufacturing, customer service, sales, and product development. A certified pool operator and CPO instructor through the National Swimming Pool Foundation, Arko is currently a water specialist for NC Brands, parent company of SeaKlear and Natural Chemistry, which is a manufacturer of pool and spa products. Arko can be reached via e-mail at terry@ncbrands.com.