Like any other feature in the overall design of an aquatics facility, there are several points to consider when it comes to your pool and the surrounding deck.
Generally, pool decks are 1.5 times the area of the pool in square footage, and decks 8 to 12 feet wide on each side of the pool are most common. Space may be limited due to physical restrictions or budget constraints, but note that minimum deck width may be specified by code and should not include the gutter grates or coping stone.
When it comes to pool deck materials and finishes, there are myriad choices, including ceramic tile, poured concrete, textured modified cement, stone, brick, wood, epoxy aggregates or pebble surfaces, rubber granules or tiles, artificial turf, mildew-resistant and waterproof outdoor carpeting, and padded and reinforced PVC membranes. Code restrictions generally prohibit landscaped sand, natural grass or unpaved areas within a 4-foot distance of the pool.
To allow for proper drainage, decks also should include proper grading, sloping away from the pool and toward deck drains or other approved water disposal sites. On average, decks should incline a maximum of 2 percent, but optimal slope may vary depending on the surface texture and the type of drains installed. Most traditional pool designs feature 4-inch-diameter deck drain inlets optimally placed at maximum intervals of 25 feet, with no more than 400 square feet of deck draining to each outlet. Another option is slot drains installed around the perimeter of the pool. Drainage systems utilizing prefabricated PVC channels with minimum 1.5-inch, and preferably 4-inch wide grates, are more typically installed today.
Expansion joints are another key consideration with pool decks. These joints are designed to spread the load around the entire deck to eliminate cracking from expansion when the material heats up or moisture content increases. Joints in the deck should be installed between the coping and the deck — and around any equipment or components installed in the deck — at a maximum of 12 feet on center.
When installing expansion joints, a flexible type of closed cell polyethylene foam backing rod should be used to provide support below the sealant and to establish a stable, continuous surface on which to apply the sealant. The backing rod should fit neatly into the joint without compacting and should not rot, swell or stain.
The sealant should not bond to the backup rod. Sealant depth should not exceed one-half the width of the joint. The joint sealing material should be highly resilient and have excellent recovery characteristics. The sealant should be of the polysulfide, two-component type. Polyurethane and silicone sealing compounds should not be used. It should create a uniform, waterproof seal. The sealant should not fail to cure or adhere, discolor, get brittle or crack due to ultraviolet light exposure, or exposure to pool chemicals.
In the pool itself, the most obvious component is the interior finish, which helps “waterproof” the gunite (concrete) shell; create a comfortable walking surface; and beautify the pool.
Traditional plaster is the most common finish, and alternative cementitious finishes for pools include colored aggregate rock finishes. Fiberglass is another option. Regardless of the chosen material, the pool surface should be sufficiently smooth to the touch. The National Plasterers Council defines "smooth" as a texture that is no rougher than very fine sandpaper (220-grit or finer) or similar to the smoothness of an eggshell.
Plumbing is another key component of the pool. Operators of older pools should pay special attention to plumbing and always consider upsizing as much plumbing as possible. Smaller pipes mean higher water velocity at the same flow rate. For example, if 100 gallons of water per minute is pushed through a 2-inch-diameter pipe, it will flow at a velocity of 10.2 feet per second. That same 100 gallons per minute will move at 6.5 feet per second through a 2½-inch diameter pipe and 4½ feet per second through a 3-inch pipe. Lower velocity means less stress on the pipes and less work for the pump. Pumps last longer and perform better using less electricity, and recent studies point to substantial energy savings from the proper pipe sizing. In addition, old skimmers and old undersized piping in aging pools should be replaced whenever possible.
With the passage of the Virginia Graeme Baker Pool and Spa Safety Act, drains have received a significant amount of attention lately. The VGB Act imposes mandatory federal requirements for suction entrapment avoidance and establishes a voluntary grant program for states with laws that meet certain minimum requirements as outlined in the act. Effective Dec. 20, 2007, the act is being administered by the U.S. Consumer Product Safety Commission. Any pool, spa or fountain with only one opening that leads directly to a pump creates an entrapment hazard. Dual spa drains that are not properly separated also can create an entrapment hazard, and even multiple suction openings can be risky if the drain covers and sumps are not sized and installed properly.
Today’s standard is dual drains (two or more drains serving a pump suction system) with openings separated by at least 36 inches. In addition, each drain cover and sump must meet the requirements of ASME A112.19.8-2007. Unblockable drains and gravity drain systems also are allowed. Safety vacuum release devices are another way to protect against drain entrapment. SVRS's must allow for the vacuum release with or without a drain cover in place and should not defeat or disengage other layers of protection installed to protect against suction entrapment.
DO’S AND DON’TS
- Do select the type of deck material and finish that is most appropriate for your situation. Consider comfort for bare feet, aesthetics and color choices. Also factor in the purchase cost per square foot, life expectancy, durability, wear and frequency of repair or replacement, cost and ease of maintenance, and bloodborne pathogen concerns (the ability to most efficiently clean up after blood or bodily fluid spills and prevent disease transmission or the spread of recreational water illnesses). Because slip-and-falls are another major patron injury risk, the coefficient of friction and slip resistance — and resiliency when someone falls on the deck — also should be considered.
- Don’t connect deck drains to the pool circulation system. The deck should not drain back to the pool or gutters surrounding the pool, as was previously a widespread practice when water-to-waste gutter systems were common.
- Do follow the manufacturer’s recommendation for properly cleaning and maintaining the deck surface.
- Don’tchoose the wrong pool finish. Many health agencies have restrictions, so check to find out which surfaces are acceptable.
- Do consider piping to allow easy connection of automatic or manual pool cleaners.
- Do have all fixtures — including diving boards, slides, handrails steps and handicap access — evaluated regularly by professionals to ensure compliance with the most recent laws, regulations and industry standards.
- Do cove the base of all walls in indoor facilities where the walls meet decks, and direct water back toward the drains.
- Do use full-depth expansion and contraction joints, not contraction only (sawcut) joints.
- Don’t get caught in the dark when it comes to drain safety standards. Information on drain standards is available through CPSC. In addition, the “American National Standard for Suction Entrapment Avoidance in Swimming Pools, Wading Pools, Spas, Hot Tubs and Catch Basins” was approved in 2006 by the Association of Pool & Spa Professionals and The American National Standards Institute. It can be ordered at apsp.org.
Pool decks should be cleaned and disinfected daily, or as needed, to prevent the spread of disease and prevent slippery biofilm growth.
In most cases, routine maintenance will depend on the deck material or finish. Many decks can be cleaned with tri sodium phosphate, but note that some surfaces must be cleaned with proprietary cleaning products.
For large decks, purchasing a commercial steam cleaner is probably warranted, but on small pool decks, dirt, grease, grime and scum can be removed by scrubbing with a stiff bristle brush and a nonabrasive, commercially available cleaning solution that is compatible with pool water (in case some of it gets into the pool).
To remove the cleaning solution, rinse the deck with fresh water using a pressure washer or garden hose with a high-pressure nozzle.
To destroy or inactivate bacteria and other disease-causing pathogens, pool decks also must be disinfected. Commercial disinfectants are available, but the least expensive tool is a mild solution of 1 part 10 percent to 15 percent sodium hypochlorite (liquid pool chlorine) to 20 parts of water onto the deck. Use an air pressure sprayer and rinse with fresh water immediately afterward.
When it comes to pool surfaces, here are the most common problems:
- Crazing (or checking) – a spider web pattern that does not go all the way through the top finish.
- Etching – corrosion of the surface usually caused by an acidic, chemical action in the pool.
- Popoffs – bond failures are the result of the top or final coat of the finish delaminating from the lower coat or even from the gunite shell.
- Tri-chlor burns – localized discoloration, etching (and, in some cases, complete localized disintegration), which can occur in pools that use tri-chlor tablets for chlorination.
- Scaling – “plaster dust” that forms on plaster finishes from calcium compounds precipitated out of pool or spa water.
- Copper scale – a greenish blue or turquoise-colored scale that eventually becomes gray. The most common source of copper is the pool heater, and the pH and alkalinity affect how much copper the water can hold.
- Calcium nodules – streaks of hard matter on the walls of the pool. Proper water chemistry can mitigate or prevent calcium nodules.
All of these problems can occur with cement-based finishes, and many can be prevented by maintaining optimum water chemistry. Water balance is a function of five factors: pH, temperature, calcium hardness, alkalinity and total dissolved solids. All of these factors are combined into a single measurement called the Langelier Index or the Saturation Index. If the index is low, then the water is called "aggressive" and plaster is easily eroded. If the index is high, then scale with iron, copper or manganese precipitates can stain the plaster.
It is possible to acid wash some finishes. Because acid washing removes cement, it shortens the overall life of the plaster. Acid washing is not recommended on plaster that is older than 10 years. If there are irregularities and exposed gunite, the pool will start to lose more water. At that time, small breaks can be patched. As breaks grow in size and number, patching is not cost-effective and it’s time to resurface the pool.
All told, pool surfacing is mainly a cosmetic problem, but improper or poorly maintained drains can present a serious safety hazard. Operators must ensure that replacement grates or covers are firmly attached — in accordance with ASME A112.19.8-2007 — to the existing sump or pool floor. Also make certain you do not to exceed the flow rate stipulated on a replacement drain cover.
About the Instructors
Hardscapes Professor Alison Osinski, Ph.D., currently is the principal/owner of Aquatic Consulting Services
Pool Surfaces Professor Rick English, has more than 30 years' experience in pool construction. English Pool Consulting is based in San Diego, and his areas of expertise include pool construction defects, solar heating and pool service. English holds engineering degrees from Rutgers University and the University of Arizona. He has significant experience as a lecturer at the University of Arizona, the University of San Diego and San Diego State University.