In recent years, rainwater harvesting has been in the spotlight as an up-and-coming system, utilizing pump stations with various levels of water treatment devices on them, harvesting water from rooftops or parking lots and then using that water for a non-potable water application, such as irrigation, toilet flushing or bus washing. Manufacturers are now seeing their rainwater harvesting systems used in a slightly different application, not only for harvesting rainwater, but also for potable water.
Installation of splash pads is on the rise. These interactive fountains normally run during the day when the temperature is warm. Alternatively, the water usage can be triggered by an action from a user (i.e., push-button or motion sensor). Because the primary user of splash pads are children, the water used in them either is from the city supply or a deep well, both considered to be potable sources. It is important to protect public health when it comes to using a water source that will come in contact with humans or has the potential to be ingested. The unique aspect that has presented itself is that this water actually can be used twice: once in the splash pad operation, and again in an irrigation or other non-potable application on the property.
A diagram of a typical rainwater harvesting system.
Water’s Path
As the water is used in the splash pad, it runs over the pad surface and then typically is sent to a drain. However, this water can be captured and plumbed to a storage tank instead, and then be used to irrigate the same park in which the splash pad is located. It also can be used to flush the toilets in the park’s restrooms.
Because splash pads are located outdoors, when it rains, the rainwater that falls on the splash pad is sent to the same drains and also fills the storage tank. This illustrates the similarities between a rainwater harvesting system and a potable water recycling system. From here, the components of the systems are identical.
Potable water or rainwater runs over the splash pad and reaches the first component in the system, the tank pre-filter. This filter is located in the gravity piping system, and contains an approximately 350-µ screen. It is used to keep any major debris that happens to make its way past the splash pad drain grates out of the storage tank. Because the splash pad surfaces themselves are hard and not organic, the amount of potential debris in the water is minimal.
The water sources themselves also are extremely clean. Potable water is clean and safe, and rainwater contains no debris unless it picks it up from the surface of collection on its way to the storage tank. Depending on the application, the tank pre-filter may be the only filter required in the entire system.
After the tank pre-filter, the water enters the storage tank, which normally is located below ground. This keeps the sunlight out of the tank, and keeps the water temperature cool, which limits any potential algae or bacteria growth. Tanks selected should be commercial-grade and H-20 load rated, even though they might not be located underneath a roadway. A piece of machinery likely will need to traverse over the top of the storage tank when completing the grading and landscape, so it is always a good idea to purchase and install a H-20 load-rated tank.
Water collected from splash pads can be used in park restrooms.
Pumped Up
The final component in the system is the pump station. This is where the water is pressurized and delivered to its end application. Pump stations should start and stop automatically, regulate a constant pressure at variable flow rate, be self-protecting with all alarms, and integrate a backup water supply should the splash be non-operational or a drought occur.
For most irrigation applications, no additional filtration will be needed as the water quality in a splash pad application is generally good. However, the water in the storage tank is now considered non-potable as it has come in contact with other surfaces and has mixed with rainwater.
When using non-potable water inside buildings (e.g., flushing toilets) disinfection may be required. This is most commonly accomplished by using an ultraviolet (UV) light system on the pump station. UV systems also require slightly finer filtration upstream, so there also will be an additional filter on the pump station normally between 5 and 25 µ in size. When filtering water down to this level, it is recommended that an automatic filter be used to eliminate nuisance maintenance trips to manually clean discharge filters. The pump station can be located outdoors or inside a building on the property.
As water becomes scarcer around the country and gains the attention it deserves, it is important that we constantly look for ways to use the precious resource as efficiently as possible. David Foster Wallace said it best: “Awareness of what is so real and essential, so hidden in plain sight all around us, all the time that we have to keep reminding ourselves, this is water, this is water.”
