Designing a ‘green’ therapy pool

by Sally Bouorm | October 1, 2011 3:07 pm

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By Barry Justus

Life is fragile. As designers and builders of pools, spas and water features, it is all too easy to become consumed with the daily rigours of operating the business that the simple pleasures in life, such as waking up pain free, are often taken for granted.

This became a reality when Poolscape was contacted last year by a couple in Milton, Ont., who were left handicapped after a motorcycle accident and were in need of a therapy pool to help with their extensive, lifelong physical therapy program.

Creating balance

To configure the pool’s design, both the clients and their therapy advisors were consulted to establish the unique design parameters the pool would require. A design that facilitated the client’s therapy requirements, while balancing the needs of their friends and relatives who would also use the pool, was important. As with any project, there is a fine line between ‘custom’ and the ability to sell the pool and home to a future owner.

Energy efficiency was also important to the client. By visiting the construction site of Poolscape’s green swimming pool[2] project in Georgetown, Ont., the client had the opportunity to view the design/build process, which helped them decide which components they wanted to include in their project.

To balance the needs for conservation, efficiency, esthetics, functionality, budget and economics, it was decided that an indoor pool, chill pool and hot sauna, contained in a frame-and-stone building, rather than a retractable enclosure, would suit the client best due to sunlight sensitivity.

Not only would these amenities help with the clients’ ongoing physical therapy routine, they would also provide a place of refuge and tranquility with views of the Niagara escarpment and a wood-burning fireplace.

The foremost concern, however, was to provide a safe therapy pool that used ‘green’ technology to minimize the long-term costs of maintaining and operating a pool of this nature.

Therapeutic features

One of the best forms of physical therapy is to exercise in an aquatic environment. The buoyancy of water takes stress off of muscles and ligaments and allows those with limited mobility the freedom to exercise. Balance also becomes easier in an aquatic environment, allowing for range of motion and mobility exercises that are not possible on land. A number of features where built into the project to facilitate the clients therapy needs.

Perimeter overflow

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A ‘soft’ knife-edge, deck-level perimeter overflow was installed for a variety of reasons. When people are using a standard pool for therapeutic exercise, water tends to get choppy and small waves develop on the water’s surface. This is not normally an issue, but with limited mobility, waves become a challenge and interfere with therapy and exercise. A perimeter overflow pool maintains precise and constant water levels where choppy water and waves are not able to develop, thus providing a safer aquatic environment.

In terms of esthetics, perimeter overflow pools are also quite striking, as the motionless water creates a glass-like effect and reflects light like a mirror when the pool is not in use. Part of the appeal of these types of pools is the soothing sounds produced by the water trickling over the wet edge into the gutter, and eventually, the surge tank. A properly designed edge and drain system produces pleasant white noise, which is especially important in an indoor environment where acoustic issues are magnified.

Pool interior details

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Careful attention was paid to the pool’s interior details. Entry steps were designed to have 152-mm (6-in.) risers (compared to the typical 178-mm [7 in.] riser), with 457-mm (18-in.) treads (normally 254 to 305 mm [10 to 12 in.]). The client decided not to install obvious handrails purely for esthetic reasons. The swim-up bar and water feature at the pool entrance, however, doubled as a handrail for accessing the pool.

All interior surfaces were tiled with bull-nosed coping to prevent injuries during therapy. These edges were further refined by wet sanding all exposed pool interior surfaces to prevent even minor scratches from occurring while exercising.

Bi-level walking track

After consultation with therapy experts, it was decided an underwater, bi-level walking track around the full perimeter of the pool would be beneficial. Part of the pool was maintained at a precise depth of 1.2 m (48 in.) and another was maintained at 1.37 m (54 in.).

This depth was determined to provide the ideal environment for the client. The water pressure, combined with walking in a controlled environment, allowed exercise to be both beneficial and safe. The centre portion of the pool was left at 2 m (78 in.) to allow for normal recreational use.

Aerated jets

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One end of the pool was reserved for aerated jet therapy massage; precise measurements were taken on site to align the jets for the sole purpose of this therapy.

Two, three-horsepower pumps were installed to power bench jets, which provide relief for lower back pains, and custom calf jets, which soothe lower leg pains.

Three variable-flow shoulder jets, powered by a variable-frequency drive (VFD) pump, were also installed to facilitate the clients’ shoulder massage therapy. All jet pumps and air blowers are precisely controlled via poolside automation controls. This particular jet arrangement, coupled with a powerful VFD pump and large diameter plumbing, also doubles as a resistance swim jet.

Constant temperatures

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Constant water temperatures in the pool and chill pool were essential to the clients’ therapy. Using a combination of geothermal and waste heat from the heating, ventilation and air conditioning (HVAC) system, the pool is maintained precisely at 29.4 C (85 F), while the indoor air temperature is maintained at 30 C (86 F). Constant air and water temperatures, combined with the heated pool deck, ensure the comfort and safety of all bathers and therapy pool users.

The standup, tiled chill pool is maintained at a precise temperature (18.3 C [65 F]) to alleviate muscle pain after strenuous therapy in the main pool. A quick soak in the chill pool is both invigorating and beneficial for tired muscles.

Safety features

Part of the design process for any project is the safety of the environment. This is especially important in a therapy pool. As mentioned previously, the perimeter overflow pool provides a safe, wave-free environment for therapy and exercise. The soft knife-edge also provides a comfortable pool edge hand-hold. Suction entrapment issues were eliminated by locating all suction devices inside the surge tank. There are no traditional skimmers or suction lines in the main pool. Eight light-emitting diode (LED) lights, in two automated zones, were also included to enhance both the safety and visual appeal of the nighttime pool environment.

Perimeter overflow pools cannot be easily covered with a standard fabric-style automated cover retracted with ropes. In this case, a unique slatted automated pool cover was installed to not only increase safety around the pool, but also to provide an insulation barrier that prevents evaporation from the pool surface.

In an indoor environment, it is critical to keep the pool covered when it is not in use. An ongoing issue in indoor pools is the control of humidity. Covers, when used properly, prevent the pool water from evaporating into the surrounding air. These types of covers can be configured to slide out of a vault in the bottom of the pool or the pool wall, or simply float out of a wet vault at pool level, as is the case with this project. Slatted covers can be fitted with built-in solar panels to help heat an outdoor pool while maintaining a layer of insulation on the water surface.

Green aspects

Although therapy and long-term recovery were important considerations, sustainability and ‘green’ design parameters for long-term cost control also played a large role in the project’s design.

Heat and water management

The client’s home was converted from electric heat to a ground source conventional geothermal loop system, which, in conjunction with the wasted heat generated by the pool room HVAC system, is used to maintain the temperatures in the pools. This type of heating is ideal for indoor pool environments. Radiant geothermal in-floor heating was also installed in the pool deck.

All aspects of the HVAC system were fully engineered to handle the loads generated by an indoor pool of this nature. Waste water from the dehumidified air is captured from the HVAC system and returned to the pool system via the surge tank. This resulted in an interesting scenario whereby the pool actually gained water over time. As such, to monitor the water level, the pool was equipped with an auto-fill system connected to the surge tank.

The source water for the pool came directly from a well with low water quality. To avoid using this water, a secondary cistern for storing clean water trucked to the site was considered. Fortunately, however, the HVAC system generated more clean water than the pool required, resulting in the installation of a waste/overflow line being installed from the surge tank to the internal bunker drainage system.

Supplemental disinfection systems (SDSs), such as a copper ionizer and ultraviolet (UV) system, provide effective water treatment. By using these systems, the client only needs to periodically add a very small amount of chlorine to maintain the proper sanitizer level.

Insulation and waterproofing

Technically, the most energy-efficient pool can be compared to a vacuum thermos. Water and heat is contained and evaporation is eliminated. There are no pumps, water features or any fun and relaxation. In reality, however, pools are used, water features are added and covers are non-existent or not used efficiently.

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The first line of defence for any pool is to prevent heat and water from escaping to the surrounding environment. Insulation is the answer and, in all cases, the greater the temperature difference between the body of water and its surroundings, the more valuable it is. Pool owners located in northern climates see a quicker return on investment (ROI) when an automated cover is installed and the pool shell and plumbing are insulated.

For this particular project, the underground bunker was a fully engineered component of the pool, deck and building foundation. Constructed of cast-in-place concrete, the bunker’s walls, floor and roof were fully insulated with rigid foam. It wraps around the entire pool shell, separating it from the earth’s cool constant temperature (12.7 C [55 F]) via an air barrier. Comprising 125-m² (1,350-sf), the bunker houses the pool’s mechanical equipment, electrical panels, automation system and HVAC and geothermal systems.

The therapy pool also has several layers of insulation (the walls, floor and plumbing are fully insulated) to help maintain and sustain the energy inputs (i.e. the heated water created by the geothermal and HVAC systems).

The floating, automated-slatted cover not only insulates the pool but also prevents heated water from evaporating into the atmosphere. Pool covers are critical to the long-term energy sustainability of an indoor pool.

Concrete is permeable and not waterproof; therefore, the pool shell interior, along with the pool deck, was coated with a combination waterproofing agent and pool interior finish to add to the water-saving aspects of the indoor pool environment. Unlike a conventional pool, however, the entire shell perimeter of this pool is visible because it is surrounded by the walk-around pool bunker, so any leaks would be highly visible.

Plumbing and pump size

Plumbing is critical to the overall performance of a perimeter overflow pool. The old mantra of ‘big pipes and small pumps’ is very appropriate. Proper pipe sizing and precise edge tolerances allow the pool to run off of a single VFD pump set to low revolutions per minute (RPMs) for energy-efficient operation.

Failure to provide sufficient hydraulic capacity (both pressure and drain lines) in the design, along with poor edge tolerances, will significantly alter the performance of the pool and lead to a large increase in energy consumption. The more narrow a pool’s perimeter-overflow edge is, the less water and pump power is required to maintain the wet edge (all pool coping is underwater).

A simple experiment, comprising a garden hose used as the surge tank water source, can be performed to test the pool’s edge tolerance. First, fill the pool to the point of spill over; then, place the garden hose in the pool and turn the water on. If the edge maintains a wet profile the pool is perfectly level. The more accurately the perimeter edge is constructed, the less water is required to maintain the wet edge, thus reducing energy costs. Engineered designs take the guesswork out of perimeter overflow systems, allowing the pool to operate properly and efficiently at startup.

Automation

A 32-zone automation system was installed to help the client operate all of the pool’s functions and features, while automatic timers are set to limit pump operations and maintain energy efficiency.

‘Smart’ pools are inherently efficient, as they do not rely on human interaction for operation. For instance, when the pool cover is closed on the therapy pool, the perimeter overflow system automatically turns off and the water circulates internally similar to a typical pool. This reduces heat loss and water evaporation that would occur if the perimeter overflow system was operating 24-7.

Different shades of ‘green’

There were a number of similarities and differences between this project and ‘Canada’s Greenest Pool[8].’ For instance, the latter project was constructed using a retractable pool enclosure. These structures can be extremely efficient provided the pool owner operates the roof and energy-efficient systems correctly (e.g. the HVAC system can be turned off for the majority of a typical pool season). This project, however, had many of the same ‘green’ systems in place but with a more standard, although energy-efficient, fixed-roof building. Both projects offer the owners long-term sustainability, safety and smart operating systems.

Many of the construction techniques and ‘green’ systems employed on these projects can be implemented on either standard projects, or complex installations. Pool, spa and water feature designers/builders should offer more energy-efficient solutions to their clients to increase the number of smart, sustainable and safe projects being installed.

 

Author note: A number of industry experts consulted on and contributed to this project, including: Gary Scott (Zodiac Pool Systems Canada Inc.), Fred Breen (Colbree Enterprises), Jake Hamoen (JTH Best Engineering Inc.), Steve Hamoen (Zonelife Inc.), Alan Thorne (Ocea U.K.) and Elena Danke (Aquafin Inc.).

 

 

Barry Justus is the owner of Poolscape Inc., a landscape contractor and pool designing and building company based in Burlington, Ont. He can be reached at barry@poolscape.com[9] or by visiting www.poolscape.com[10].

 

Source URL: https://www.poolspamarketing.com/trade/designing-a-green-therapy-pool/

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