Water Savings in Pools and Spas

It is difficult to determine how much water an average swimming pool uses. However, by comparing homes with and without swimming pools and correcting for differences in landscape size, it is estimated that single-family homes with a swimming pool use about 58% more water outdoors than single-family homes without a swimming pool. This research indicates that the addition of a swimming pool results in a substantial increase in water use.

Covering the pool installed at single-family homes, however, will reduce water loss due to normal evaporation. The cover can also reduce heating bills up to 50% by preventing night heat loss and will also save on chemicals. Pool covers come in a wide range of types and costs, and it is important to make sure the cover fits properly.

Swimming pools installed at multi-family buildings primarily lose water by evaporating from the surface, cleaning the pools via backwashing filters, and maintaining overall water quality standards. To mitigate water losses from these sources, the U.S EPA WaterSense® program recommends that the pools be independently metered to detect leaks and perform maintenance before significant water loss occurs. WaterSense also recommends that pools be designed to reduce water losses from splashing by redirecting or catching the splashes (e.g., overhanging edges, perimeter gutter, and grate systems).

In addition, WaterSense recommends that the pools be equipped with water filtration systems using sorptive media or cartridges that use less water during backwashing than other filtration systems such as sand. Sorptive media filters include conventional diatomaceous earth (DE) or perlite filters and regenerative filters that reuse the filter media. These filters remove particles down to 5 microns in size, while sand and cartridge filters work in the 10- to 40-micron removal range. Sorptive media filters have hundreds to sometimes more than 1,000 fabric-coated tubes inside a pressure container. The medium (DE or perlite) is made into a slurry and mixed with the water in the filter. The medium is then deposited on the tubes by the water being pumped through the filter. Conventional sorptive media filters must have the DE or perlite replaced after each backwash. With regenerative sorptive media filters, the medium is periodically “bumped” off of the filter tubes by backflow, air agitation, mechanical shaking, or a combination of the three. It is then recoated onto the filter cloth. No water is lost in the recoating process. When the medium is flushed, only a few hundred gallons of water are needed. This makes regenerative sorptive media filters very water-efficient.

Water-efficient cartridge filtration systems use reusable filter cartridges that do not require backwashing to clean the filters. In this type of system, two sets of filters are required and each should last two to five years. When one set is removed for cleaning, the other set is installed in the system. Reusable filter cartridges must be soaked in a cleaning solution, then brushed and rinsed off prior to reuse.

Covering pools during long periods of inactivity, when possible, will also aid in reducing water losses through evaporation.

It is recommended that builders should work with landscape professionals to ensure that the surface area of a pool or spa installed at a single-family home is included when conducting a landscaping water budget using the WaterSense® Water Budget Tool. The pool or spa surface area is treated as turfgrass in the tool.

For information on energy-savings pool pumps see the guide Variable Speed Pool Pumps.