The tradition of running through a backyard sprinkler is a classic summer activity, but the question of whether the water is safe for play is a valid one. The safety of water used in a residential sprinkler system is not absolute and depends on multiple factors, primarily the source of the water and the environment it enters. While the water may begin as potable, its quality can change significantly before it contacts the skin or is accidentally ingested. Potential risks involve chemicals, biological hazards, and the delivery system.
Water Source Determines Safety
The initial quality of the water is determined by its source, which generally falls into one of three categories for residential use. Municipal water is typically the safest starting point, as it has been treated with disinfectants like chlorine and regularly tested to meet federal drinking water standards. This treatment process effectively removes most pathogens. Private well water, conversely, is unregulated by federal standards, making its safety the responsibility of the homeowner. Wells can be contaminated by runoff or contain naturally occurring contaminants like arsenic, radon, or high levels of nitrates, which are particularly concerning for young children.
The third source, gray water or reclaimed water, carries the highest risk and should be avoided for any form of recreational contact. Reclaimed water is municipal wastewater that has been treated for reuse in non-potable applications like landscape irrigation. While treatment is extensive, it may still contain residual chemical or microbial contaminants that pose risks through dermal contact, aerosolization, or accidental ingestion. If a home uses a separate system for gray water irrigation, it should never be connected to a child’s play sprinkler.
Chemical Contamination from the Yard
Even water that starts clean, such as municipal tap water, can pick up harmful substances once it is sprayed onto the lawn. Common lawn care products introduce external chemical risks to the water and the immediate play environment. Pesticides and herbicides, designed to kill weeds and insects, can be carried by water runoff or absorbed into the ground, contaminating water that pools. Accidental ingestion or prolonged skin contact with water exposed to these chemicals, which can include ingredients like 2,4-D or organophosphates, presents a health concern.
Fertilizers also pose a risk, as they contain high concentrations of nutrients like nitrogen and phosphorus salts. If ingested, these chemicals can cause issues. Furthermore, the garden hose itself can be a source of chemical contamination. Studies have shown that water sitting stagnant in a hose, especially one heated by the sun, can leach chemicals like lead, bisphenol A (BPA), and phthalates from the hose materials. Lead levels found in water from new garden hoses have been measured up to 18 times higher than federal drinking water standards after the water was allowed to sit and warm.
Understanding Biological Hazards
Biological hazards in sprinkler water often originate not from the water source, but from the hose system and the environment. Warm, stagnant water trapped inside a garden hose is an ideal environment for the growth of bacteria and the formation of biofilm, a slimy layer of microorganisms. This is often referred to as the “first flush” risk, where the initial blast of water from a hose left in the sun contains the highest concentration of these microbes. Among the potential pathogens is Legionella bacteria, which can colonize the hose biofilm and grow to concerning densities.
The mechanism of harm from these bacteria is significantly amplified by the sprinkler’s function: aerosolization. Sprinklers generate a fine mist of water, creating inhalable particles that are 10 micrometers or smaller. When Legionella is present in the hose, this mist can introduce the bacteria directly into the lungs, causing serious respiratory illnesses like Legionnaires’ disease or Pontiac fever. Water that pools on the ground mixes with soil bacteria, animal fecal matter, and other environmental contaminants, increasing the risk of exposure to pathogens like E. coli or Cryptosporidium, especially if children accidentally swallow the water.
Simple Safety Measures for Playtime
Mitigating the risks associated with sprinkler play is straightforward and begins with managing the hose. Before a child starts playing, it is important to “flush” the hose by letting the water run for several minutes until it runs cool. This clears out the stagnant, chemically and biologically contaminated water. Hoses should be stored in a cool, shaded area when not in use to prevent the sun from heating the water and accelerating the leaching of chemicals or the growth of bacteria.
Supervision is necessary to prevent excessive swallowing of the water, which is the primary route of ingestion for contaminants. If a private well is the water source, annual testing for total coliform bacteria and nitrates is recommended, with additional testing for contaminants like arsenic. Homeowners should avoid using the sprinkler immediately after applying chemical lawn treatments, allowing time for the products to dry and settle. Installing a hose bibb vacuum breaker on the outdoor faucet is an inexpensive step that prevents contaminated water from being siphoned back into the home’s drinking water supply during a pressure drop.