Hundreds of pool and spa professionals packed into conference rooms at the AQUA Show and the International Pool & Spa Expo this fall to talk about the problem. It's been the focus of several trade magazine articles, and since 2001 the state of California has invested over a million dollars to educate builders and retailers on the issue.
What's all the hubbub about oversized pumps? They've been turning over pools without much comment or incident for more than 50 years. And if they've been a bit huskier than necessary, what's wrong with a little extra horsepower in the circulation system. Most people, indeed most customers, see that as a positive.
Unfortunately, it's not. While "a little extra horsepower" may be useful under the hood of your car, in a pool circulation system, it's very bad news.
The reason is found in the physical equations that govern fluid flow through a pipe.
Most of the time, our natural laws offer no bargains.
That is to say, most equations of physics are linear. If a new model of car is a pound lighter, for instance, its force in a crash at the same speed is a pound less.
But when it comes to pool water in a pipe, friction losses go up exponentially with increased .ow. And therefore, so does waste, in terms of kilowatt-hours, and the pool owner is paying for it.
If the industry can be shown how to circulate pool water using smaller pumps, the implications for its customers are huge — and getting larger with each utility rate increase.
Because the pump is such an energy hog, a pool owner's savings in utility bills can be eye-popping. Scott Clay, program manager for Pacific Gas & Electric in San Francisco, estimates the savings for a typical California pool owner (where rates are higher than most states) switching to an energy-efficient motor and pump using lower head to be $600 per year.
In 10 years, that's $6,000 in utility bills alone — to say nothing of the enormous savings in the cost of premature component failures. Tack that on to the bill, too. High .ow rates can damage filters, heaters, plumbing components and pumps. For example, with too much water coming through under high pressure, sand filters become channeled, and DE filter grids are prone to collapse.
It all adds up to high pool-operating costs, a drag on future sales and needless depletion of resources. In the state of California alone, according to Clay, it takes three fully functional power plants to provide the electricity that is wasted by pool pumps. If every pool owner in the state would switch to a less-costly, more-efficient pump, the state could actually shut these power plants down — or use them to meet growing demand instead of building new ones. Scale these figures across the United States and they show that the effort to promote sensible pool-pump sizing and lower line speeds could have a real impact on the overall energy consumption (and energy dependence) of the entire nation.
Power Costs
The problem, in a nutshell, is that too many swimming pool pumps are oversized. That means that .ow rates are frequently too high, and the faster you try to put that water through the system, says Steve Gutai, Waterpik Technologies' product manager for pumps, filters, valves and water features, the more resistance is created.
At this point, the pump is really wasting electricity. To quantify that, Clay's group at PG&E has done some calculations. "The staggering part, as far as the cost to the California customer is concerned, is that by using that amount of energy just for the pool, their overall usage goes up into the higher tiers of our rate structure. In California, the more you use, the higher rate you pay.
"So based on these penalties, a Central Valley pool owner may be paying an extra $50 to $80 per month to operate their pool pump. By switching to an efficient motor and two-speed pump, they can save that."
For the utility that Clay represents, and ultimately, the general public it serves, the timing of usage is just as important as the amount. "Pool pumps run at the peak hours of energy usage," he says, "from noon to six. That's when everybody in California uses their air conditioning and so on. So reducing the load of these pool pumps means a whole lot in terms of reducing peak power."
Downstream Failures
In addition to wasting scandalous amounts of energy, oversized pumps result in higher noise levels and premature equipment failure, notes Skip Phillips, owner, Questar Pools and Spas, Escondido, Calif.
"Let me give you an analogy," he says. "It's like sticking a 500-horsepower engine in a Mini Cooper. And we're not going to change anything, we're not going to redesign the transmission, we're just going to let it selfdestruct. Everything downstream gets over-pumped."
That's true, agrees Gutai. "If your pump is oversized, you could potentially cause damage to the filter components and your filtration system will not be as efficient.
"If you have a sand filter it will cause channeling as the water drives itself through the sand bed too quickly, resulting in poor filtration. If you have a cartridge filter or a D.E. filter, it will contribute to the collapse of the cartridge or the grid."
Human Nature
If oversized pumps are so expensive to run and are so hard on the circulation system, why are so many of them in service?
Human nature. Pervasive myth. If the pump is the engine of the circulation system, then the biggest, strongest engine is best, isn't it.
Of course the answer is no, but to many people, both outside and inside the pool industry, this myth is just common sense, applicable to machinery in general; planes, trains, blow dryers — you name it.
And while few contractors will say so on the record, it is a fact that many builders try to win sales with bids that include higher-horsepower pumps than are necessary. They do this because it frequently works; the horsepower myth is accepted by most customers as a simple and obvious truth. To them, the contractor that is offering a higher-horsepower pump is offering a better pool.
Particularly in the highly competitive above-ground market, where buyers often compare advertisements from two or more retailers, the spec with the 1-horsepower pump looks better than the one with the - horsepower pump.
"People are convinced that their system is being degraded if they fail to have these high-horsepower systems," says Phillips.
At this point in the sales process, notes Rob Stiles, product manager, pumps, Pentair Water Pool & Spa, Sanford, N.C., efficiency can be an awkward topic, because it forces the salesperson to focus on the ongoing energy costs associated with pool ownership. "You've got to explain to someone that it's going to cost them money even after the pool's paid for," he says. "And that's not something that a lot of people in the pool business want to talk about."
Slow It Down
The key to efficiency, whether you sell on it or not, is lowering the flow rate. Reduce flow rate, says Clay, and you dramatically cut the electric bill. "There's a law of physics at work here called the affinity law," he notes. "And what it states is that, in an ideal system, when flow is reduced by onehalf, the energy draw drops by oneeighth. What we find in a real system is that it actually drops by one-fifth."
The needs of the pool, of course, must not be sacrificed in the process. One good way to meet equipment needs and still save the maximum amount of energy is by installing a two-speed pump.
A two-speed pump has a high speed that runs at 3,450 rpm and a low speed that runs at 1,725 rpm. The high-speed mode is useful in highbather-load situations or to address other system needs. The low speed isused for normal filtration; when you drop the motor speed to half, efficiency goes through the roof.
"The typical 1 1/2 or 2-horsepower pump runs at about 9- to 14 amps," says Clay. "So when you drop that same size pump down to half speed, you're drawing between 2 and 4 amps. That's a huge difference, even after you factor in the fact that at half the .ow, you have to keep it on twice as long. Taking that into consideration you end up using between one-fourth and one-half the energy."
At the same time, pump manufacturers are introducing new products to help solve the problem and save consumers money. For instance, Pentair recently introduced a pump with a variable-speed drive, according to Stiles.
"It uses a processor and a computer to size itself to the system," he says. "You input pool size (say 20,000 gallons) turnover time, and when to run (10 hours, between 8 a.m. and 6 p.m.), and the pump will calculate the most efficient point to run."
Resistance
While new products are arriving on the market and awareness is growing, change takes time. Clay has been working to educate Californians on the need and the means for change for the last three years. His group is part of a strong push by electrical utilities in the state for pool pump downsizing with education programs and generous rebates to homeowners — as much as $300 for downsizing to a two-speed pump and energy-efficient motor.
And in his three-year effort to fight excess resistance in pool plumbing, Clay has encountered some resistance of his own. "When we went to the pool service association meetings," he says, "and came to the subject of [switching to] two-speed pumps, the congregation would get kind of unruly. Many of them felt they would not work on pools.
"We heard things like: 'You don't get enough flow in the pool to get good circulation. There's not enough flow to make the weir skimmer work. Not enough pressure to make the pressure cleaner move around the pool or to fill the solar heating panels.'"
Good pool circulation is not an issue with lower line speeds, Clay says. In fact, it is improved. He points out, for instance, that a pool that is turned over in 16 hours at low flow and then sits for 8 hours will provide cleaner, better-mixed water than one that is circulated 8 hours at high flow and then sits for 16 hours.
And where necessary, he says, the pressure needs of the solar panels and the automatic cleaner can be addressed by starting a two-speed pump on high speed for an hour or two, and then once the solar panels are full or the automatic cleaner has performed its job, reducing to low speed.
Phillips's experience has been similar to Clay's. After teaching seminars on pool circulation, Phillips has come to believe that most industry personnel are unaware of the problem of oversized pumps — and are contributing to it. In class, he displays what he calls a "typical" pool circulation system — which includes an oversized pump. "And everybody's in there nodding, saying, 'Yeah, I do that.' And then I tell them there's absolutely no justifiable reason to do that."
Clay believes the message is getting through in California, with the combined effect of education and customer rebates. "We're starting to win folks over," he says, "but it's been a hard road."
California: Land Of The Efficient Pumps
Necessity is the mother of attention, to tweak an old adage, and in some ways the emergence of oversized pumps as an issue is a result of the California energy crisis. Says Stiles, "I think what gave the big kick to the industry to start moving was the state of California and everything that's happened out there in terms of efficiency."
With energy prices still astronomically high by most standards, the pressure to conserve has produced tangible gains, he notes. "Now they've got guys running pools out there on a third of a horsepower, when in the past you might see a two- or three-horse pump on there."
There's a long way to go, however. It is a classic issue of industry maturity. Growing pains. Thirty years ago, notes Gutai, when pools were simple and energy plentiful, having a higherhorsepower pump hardly mattered. It's different now.
"Projects today can be much more complex," he says. "Now you have multi-level pools with vanishing edges, with gravity feed systems, with extensive water features and spas. And swimming pool builders understand that to execute a job like that, where they can make a lot more money, they need to understand fundamental concepts of hydraulics."
In assessing progress, Gutai is optimistic: "Across the nation, I think pool builders are getting more and more attuned to this problem. I think they're learning the proper way to size pumps."
Plumb Properly
According to the Residential Pool Standard established by NSPI (soon to be administered by the International Aquatic Foundation), in no case should water velocity be greater than 10 feet per second at the pump outlet or 8 feet per second at the pump inlet using PVC pipe. For copper, 8 feet per second is the maximum.
