Web Exclusive - July 2021
Find a printable version here

Circulate Savings With the Right Pump

By Mike Fowler


Proper pump selection and optimal flow rates are extremely important to ensure proper flow, avoid "dead spots" in the pool and ultimately save energy and costs. Pool professionals have a unique opportunity to increase the energy savings with properly sized pool pumps, especially for commercial pools. Because new Department of Energy regulations on variable speed pool pumps goes into effect in July 19, 2021, this is the year for pool professionals to proactively educate commercial pool operators and aggressively make pools energy-efficient using variable speed pool pumps. With a few tips and rules of thumb, proper pump selection will result in better water flow while minimizing energy consumption.

Properly Sizing Pool Pumps

Affinity laws indicate that the power demanded by a pump is proportional to the cube of the flow rate. For example, if the pump's flow rate is doubled, then its power demand is increased by a factor of eight. Therefore, it is important to utilize the smallest pump that is capable of completely turning over the pool water in an acceptable amount of time.

During the pump selection phase, the facility's auxiliary features (e.g., spray pads, fountains and waterfalls) should also be considered, as it is common for them to use the pool's main pump. Some building codes, however, require the use of a multi-speed pump, or in some cases, a separate pump for each auxiliary pool load. Pumps on many pools are oversized by design, sometimes more than 20% to 40% bigger than they need to be; this happens because many architects and engineers look at what is required, then pick the next size up to be sure the pump can handle the job.

Here are a few tips to help ensure you are installing the best pump for the pool:

  1. Determine flow rate in gallons per minute.
  2. Calculate total dynamic head (TDH—the pressure head difference between the inlet and outlet of the pump) to account for friction loss. Adding 20 feet of head for a dirty filter is optional.
  3. Refer to the pump's performance curve to select the preferred unit.
  4. Locate the required horsepower of the pump by plotting GPM vs. TDH (if plotted point falls between two pump sizes, select the next larger pump size in terms of horsepower).
  5. Do not oversize the pump. Choose the best pump available for the facility's flow rate requirements (i.e., do not install a 20-hp pump where a 10-hp pump will suffice just because that is all that is available). If the preferred pump does not provide a proper fit, consider a different pump model.
  6. Verify that the selected filter can handle the system's flow rate and be sure the minimum backwash flow rates can be achieved.

Proper Circulation

Properly balanced plumbing and properly placed return lines are two solid ways to make sure a swimming pool is designed and circulated to eliminate "dead zones" of circulation in commercial aquatic facilities. As any pool service professional knows, dead zones lead to problems with water chemistry, algae growth and other water maintenance issues. Therefore, avoiding dead zones is key to ensuring a clean and clear pool.

One of the most important parts of a well-balanced, circulated pool is having a hydraulically sound plumbing layout throughout both the suction and the return sides of the system. Taking larger pipe sizes to the pool and then breaking them down to smaller sizes in a balanced way around the pool will ensure that you have proper circulation throughout the entire body of water and don't leave any dead spots in the pool.

Proper placement and directions of return lines is also key to avoiding dead zones. When bringing water back to the pool after it passes through the filtration system, the whole key is to make sure it goes back to the pool completely and as evenly distributed as possible. Once again, the importance of balancing your piping around the pool and location of the returns will help to make sure that all areas of the pool are circulating water.

Many contractors today will align the return lines throughout the pool so the water is returned in a circular motion around the pool and designed in such a way that as the circulation around the pool is complete the water is also passed by skimmers in a strategic fashion to aid in cleaning the surface, as well as distributing the water. One suggestion is to cap the end of the return-line plumbing to increase the performance of those returns that are furthest away in your plumbing layout. This will ensure that all areas are getting proper circulation around all spots of the pool.

In larger pools, it often makes sense to divide the plumbing and pumps into three sections, each with their own pump system. In this way, each section of the pool is its own "zone" and the equipment and plumbing is set up for each zone.