The Foundation for Pool & Spa Industry Education has completed a study on how to save energy without compromising water quality.
The study looked at a small, swim-school pool to explore the performance of energy-efficient equipment in commercial vessels of less than 30,000 gallons. Future projects are expected to evaluate larger installations.
FPSIE performed the study for the Sacramento Municipal Utility District and the Davis Energy Group, hoping it will influence government regulations and incentives.
For the study, FPSIE modified the suburban Sacramento, Calif., pool to make it more energy efficient. This resulted in a 75- to 80 percent decrease in energy usage from the circulation system, said Michael Orr, executive director of Sacramento-based FPSIE.
Orr believes that smaller commercial pools, such as those found at hotels and apartment complexes, could see at least a 66 percent reduction in the cost of energy coming from the circulation system.
“Currently, most of them are paying around $4,500 a year for circulating their water,” Orr said. “They could cut it down to about $1,500.”
For the study, volunteers donated and installed high-efficiency heaters and a variable-speed pump, and modified certain aspects of the pool’s plumbing to increase efficiency. For example, they added four venturi jet returns to one wall of the pool, positioning them to face downward while streaming in a circular pattern toward two skimmers on the other side. The newly filtered water is returned toward the floor and, as a result, pushes the dirtier, unfiltered water up toward the skimmers.
In many pools, with returns set 12 to 18 inches below the surface and pointed straight out, the same water is passed through the skimmer and filter repetitively, leaving a significant portion of the gallonage untouched. In this common scenario, it can take four turnovers to filter almost all the water, Orr explained. With the configuration used on the study pool, the idea was to continuously push new water through the skimmers.
“We did a number of dye tests to prove this,” Orr said. “When we started out, it took over 1½ hours before we got the whole pool dyed. After our modifications of the jets, it took us about six minutes. We found out an awful lot.”
If the water can be filtered more efficiently and thoroughly, it is hoped there will be less pressure on commercial facilities to turn their pools over every four hours, particularly when they aren’t in use. Ideally, Orr said, regulators would allow operators to run variable-speed pumps on low when there are no swimmers in the water, rather than requiring the pumps to be set on higher speeds all day.
“I’m hoping that ... [state regulators] will give the local environmental health departments the authority to set the number of turnovers based on the technology of the equipment they have,” Orr said. “Everybody will win if we can get the regulations changed to allow this to happen in commercial pools.”
In the case of the study pool, the pump ran at 60 gallons per minute during operation hours, but went down to 30 once the school was closed. “That’s where we really saved energy,” Orr said. “For every hour that the old pump was using 1,200W energy, now we were only using 250W at 30 gpm.”
Orr also rearranged plumbing in the equipment room, placing the equipment and piping around the perimeter of the pad to help limit the number of hard 90-degree elbows needed.
FPSIE originally had planned to outfit the pool with ultraviolet sanitation and an alternative filtration medium called sphagnum moss, hoping to show that options other than chlorine should be considered in commercial codes. However one of FPSIE’s partners in the study chose not to move forward with those portions.