The Age of the Pool is Over. Long Live the Spool!

If your client wants a swimming pool, try talking them into a sustainable spa instead.

Swimming pools are becoming an ever-bigger concern in dry states. According to the Arizona Dept. of Water Resources, “half of the potable water Arizona homeowners use is outdoors.” Pools and spas account for approximately 16 percent of that outdoor water use.

Efficient Pool Products Make a Splash


Using a fraction of the water but no less luxurious, spas are generally a more sustainable choice than a swimming pool.

In Arizona, a standard (16 ft. x 36 ft.) uncovered pool loses four to six feet per year to evaporation—that’s 17,235 to 25,852 gallons. Most of this loss occurs during the summer. Added to the water lost during refilling and backwashing, that’s roughly the equivalent of filling the pool every year. Draining a pool doubles this amount. This is why, if you do own a pool, it’s extremely important to use a pool cover, which can reduce evaporation losses by up to 30 percent.

Spas, on the other hand, if used wisely, can more or less break even with a home that has no outdoor water features at all, according to experts. Here’s the deal, according to the Association of Pool and Spa Professionals:

“Baths use water once, whereas a spa offers four to six months of use for the same water. Taking just five baths, at 80 gallons each (normal tub size), uses enough water to fill a typical 400-gallon spa.” Filling and draining a bathtub twice a week for four months uses 2,720 gallons of water. A spa uses the same 400 gallons of water continuously throughout those four months.”

Hot Tub Blanket

A spa blanket doesn’t just keep the heat in; it also reduces water loss from evaporation and keeps water away from the hot tub cover.

Of course, nothing is quite that simple, and it’s important to consider overall environmental impacts. Spas typically require chlorine and other chemicals to keep water from becoming unsafe. Bathtubs don’t. So there’s an added burden with treating and discharging spa water.

Recycling graywater from the bath and using it to irrigate landscaping helps mitigate the higher overall water use of bathtubs. In fact, depending on the region, the success of a graywater system depends on having a regular source of graywater, such as a weekly bath.

On the other hand, a spa is almost always less water intensive than a swimming pool, especially a pool without an evaporation cover. A spa’s smaller volume and surface area means less water is lost to evaporation. But again, the big picture score sheet is more complex. Spas also tend to be kept at much higher temperatures than pools, thus consuming more energy.

One can imagine a water-thrifty family that switches over from weekly baths to regular visits to the spa, in effect relying on recycled water instead of virgin potable H2O. The challenge is how to minimize chemical use, both for the sake of human health and hygiene, and to address energy consumption. We predict that with the continued development of UV treatment and other “clean” tech methods, recycled water applications will likely play a bigger role in the spas of the future.

The trend toward “spools” (and away from large swimming pools) is definitely a move in the right direction. But in the end, human behavior will determine just how much the presence of a spool affects the overall household water use.

Sustainable Spas

If your client insists on a hot tub or ”spool” (spa-pool),  be sure to provide these tips for reducing its environmental impact.

  • Cover it. As with swimming pools, covers minimize evaporative loss and keep the water cleaner; they also keep the heat from escaping. Foam-core covers come in different thicknesses and foam densities; some even include a reflective metal shield that directs heat into the water. Using a “spa blanket”—also called a floating thermal blanket—in addition to a cover will insulate the water even more.
  • Create a windbreak. Shielding a spa with fencing, panels or vegetation can reduce heat loss from wind.
  • Mind the thermostat. Lowering the temperature by a few degrees will cut energy use. If you are going on vacation, lower the temperature even further or, if you’re going to be away for more than a week, consider turning it off altogether, unless there is a danger of frozen pipes.
    Heat off-peak. You can program your spa to heat during off-peak times, when energy costs are lower.
  • Cool the jets. Air induction jets cool spa water. More efficient spas use adjustable hydro jets which recover heat from the equipment cabinet rather than using a motor-driven blower.
    Size right. If purchasing a new tub, look for the specs. A unit with a high R-value, low wattage, a smaller pump and lower volume will consume less energy.
  • Heat with the sun. A solar thermal system will preheat water, cutting the energy required to bring it up to temperature.
  • Go natural. Mineral and enzyme-based alternatives to chemical treatment are not just better for the environment; they are also gentler on skin and recommended for chemically sensitive people. Ozonators can be used in conjunction with natural products, or can reduce the amount of chlorine or bromine needed.
  • Keep it clean. Your spa pump won’t have to work as hard if you regularly clean and change filters. The water will also stay cleaner longer.

Flat plate and evacuated tube collectors are two technologies commonly used to capture solar energy for water heating.

Sun tubs

For guilt-free hot tubbing, consider heating the water with the sun. A few companies offer kits, which typically include solar collectors, a heat exchanger and a solar-powered pump. Some offer storage as well. Kits will set you back at least $1,500, but once installed, they can save several hundred dollars per year in heating costs.