The Anatomy Of A Splash Pad
By Jonathan Allred
Although the completed water feature looks simple, the splash pad system and initial design are complicated. The anatomy of a splash pad is similar to that of a pool and demands similar attention, particularly to water-quality and sanitation issues. There are many options presented to potential customers—not all of them comparable—and the choices may be confusing, even conflicting. This article outlines the basic system that makes up the splash pad and discusses several of the critical design and operational issues.Because splash pads and spray decks provide wet entertainment with relatively low maintenance, they are a popular option for cities, homeowners’ associations, retail developments, and even private residences. A splash pad consists of one or more deck areas fitted with a combination of various nozzles and may include above-ground “spray toys,” (umbrellas, flowers, hydrants, tipping buckets, etc.) intermittently spraying, squirting, dumping, or gushing—while kids of all ages dash from feature to feature, thoroughly enjoying themselves.
A Detailed Design Plan
The first consideration in planning any type of water feature is hiring a design/engineering firm and consulting with local health and building departments that oversee the construction and issue permits for such projects. These organizations will explain what is needed to comply with local codes, which vary, sometimes substantially, between jurisdictions.
Once a team is in place, design can begin. Site selection is critical, as is location. Details such as accessibility and parking, as well as proximity to nearby businesses, should be considered. Shape and contour of the site can be accommodated in unique and interesting ways. Splash pads do not need to be round, or square, or even flat—use your imagination! Research the types of features that are available, but don’t feel limited to choosing from a single supplier.
Each spray feature or toy has a specific “wet zone” or spray area, a required flow measured in gallons per minute (gpm), and a pressure rating (psi) from the manufacturer. The spray area defines how close to the edge of the splash pad that feature may be placed. Overspray makes a muddy swamp out of the surrounding landscape. This is also the time to determine the shape and slope of the deck—usually greater than 1:50 (2 percent slope) but less than 1:15 (7 percent)—to retrieve all of the water in sufficiently sized drains. The surface of the splash pad should get some attention as well. The finished surface needs to be resilient to foot traffic and made of a nonslip material. There are several resilient surface options that can reduce slip-and-fall injuries (to a degree) and provide a unique appearance. However, a simple broom-finish concrete is often the best and least-expensive option.
Designing an attractive landscape and providing shade are important elements of the design as well. However, be aware that children will often make tiny boats to ride any streams of water available in the surrounding landscape. For this reason, identifying local codes and designing for compliance are important. One violation will shut down a new splash pad, and re-design or field modifications are never fun.
With the size of the splash pad defined, landscape outlined, and the features set in place, it is time to create the mechanical system that will bring it all to life!
A Tale Of Two Systems
Starting with technical data from the selected features, the engineer sizes a system to deliver the necessary flow and pressure through a piping network and to the individual features. Two types of systems can be considered:
A flow-through system is the simplest and works well on smaller splash pads with fewer than 20 nozzles. Potable water from a municipal line (or in some approved cases, a well) can be directly connected (with approved backflow prevention) to the pipe network. Alternately, if sufficient city-water capacity is not readily available, it may be used to fill a tank or cistern sized for the needed capacity, and the water is then pumped to the features. By using a controller, only a certain number of sprayers can be activated at one time to limit the flow demand. Water from the feature nozzles runs across the sloped deck to a collection drain. In some cases, this may be the last time water is seen before it is sent to the storm drain or sewer line. However, many facilities find that flow-through splash pad water can be collected, stored, and used for landscape irrigation, thus conserving water. This type of system does not require filtration or a sanitizing system because water does not recirculate.
The second system uses an independent, recirculating treatment system that filters and sanitizes the water contained in an underground storage reservoir, or catch basin, similar to that of a swimming pool treatment system. Typically, the pumps that power the spray features operate independently from the treatment system. Water draining off of the splash pad is collected and returned to the reservoir to be treated and re-used.
Addressing Issues In Advance
One common issue in creating a splash pad is that the filtration and sanitation are often inadequately sized. A great splash pad design that draws a large crowd can also easily overwhelm the treatment system. Designing to minimum code requirements is almost never sufficient. One park that recently opened in Springville, Utah, projected a visitation capacity of 100 people, but has experienced occasions where there are as many as 600 visitors at a time, and more than 2,500 in a single day. The high ratio of patrons to water volume in a feature means a high demand on chemicals to sanitize the water. Ensure that visitation projections are realistic and that the engineer includes this projection in sizing the treatment system. If there is any question, oversize!
Due to the high bather/water ratio (imagine 2,500 people per day visiting a hot tub), operators often battle rapid chloramine buildup in the water. Chloramines are the byproduct of chlorine sanitation created when contaminants combine with low levels of chlorine in the circulated water and that need to be removed through oxidation so proper free chlorine levels are maintained in the water. For this reason, the enclosed reservoir must have plenty of ventilation to prevent a build-up of off-gas. Without proper ventilation, chloramine levels are more difficult to control since the off-gas dissolves into the water, forming even stronger chloramines. Chloramines are also highly corrosive due to the moist environment inside the tank and will quickly rust metal (even stainless-steel) fixtures and fasteners.
The choice of sanitizing chemical is also important. Trichlor or dichlor tablets contain cyanuric acid (CYA), which is unnecessary and reduces the effectiveness of the available chlorine. CYA levels build rapidly due to high turnover and chlorine demand, requiring frequent draining and refilling to keep these levels down. Liquid chlorine (sodium hypochlorite) and calcium hypochlorite are typically the best solutions in combination with an acid feeder for pH control. Ozone is highly recommended as a secondary sanitizer, both for its extremely efficient sanitation (reducing the potential for waterborne illness) and for its oxidation power to remove chloramines.
Let The Good Times Flow
If the challenges are properly addressed, there are many benefits to opening a splash pad. For example, the Springville splash pad has contributed substantially to increased business traffic in the small downtown area, with patrons traveling from considerable distances to visit. Local shops, restaurants, and even the city library are reaping the rewards of having a steady flow of splash pad customers. While other surrounding communities routinely shut down for maintenance or high chloramine levels, Springville, because its water quality is excellent, has enjoyed the benefits of an uninterrupted, low-maintenance operation.
With careful planning on a city’s part, patrons of all ages will enjoy a new splash pad for many years to come. The investment and effort are well worth it!
Jonathan Allred is a senior designer for Cloward H2O located in Provo, Utah. Reach him at firstname.lastname@example.org.