Make-shift Pools and Essential POU Maintenance
With everyone stuck at home and community pools shut down, stock-tank pools are having a moment.1 These galvanized metal containers are staples on farms and ranches for watering livestock and are now being fashioned as backyard swimming pools. While they have a cute, rural-chic style, keeping them clean and preserving the water quality requires focused intention.
Designing your own
An inexpensive alternative to building a pool, stock tanks cost only a few hundred dollars compared to an in-ground swimming pool at tens of thousands of dollars. They can be purchased at your local animal feed or tractor supply store and will likely last longer than the plastic kiddie pools or above-ground alternatives. Stock tank shapes vary from oval, square and round options (with round tanks being the most popular for swimming) and range in size from six- to 10-foot (1.82- to 3.04-meters) diameters, holding 80 to 800 gallons (302.83 to 3,028.32 liters) of water. This makes for a weighty pool, so finding a solid, smooth or soft spot in the grass or sand to set the tank is important to avoid punctures and leaks.
Harmful microbes naturally persist in tap water or hoses used to fill your stock-tank pool. Because swimming activities lead to exposures to harmful microbial contaminants (such as bacteria, protozoa and viruses) via ingestion, inhalation and skin and mucous membrane contacts, no one should swim in any pool until it is properly treated with chemical disinfectants and filtration equipment. Naturally occurring water-based organisms of concern include Naegleria fowleri (also known as the brain-eating amoeba) and Pseudomonas. Two cases of the almost always fatal Naegleria fowleri have occurred in previously healthy children swimming in untreated pools or bathtubs.2 The organism is readily found in lakes, holding tanks and water taps, particularly in warmer climates.3 Some strains of Pseudomonas cause ear infections (swimmer’s ear) and can infect hair follicles, leading to the well-known hot-tub rash.
Other microbes found on skin and in urine and feces may be introduced to the water by swimmers. Examples include, E. coli, rotavirus, norovirus and Cryptosporidium (which can cause mild to severe diarrhea and vomiting) and drug-resistant Staphylococcus bacteria (i.e., Staph and MRSA), which can cause unpleasant and sometimes serious skin infections. From 2000-2014, 493 disease outbreaks occurred due to exposure to treated recreational water, resulting in over 27,000 cases of illness and eight deaths.4 Treated recreational water outbreaks are most commonly due to chlorine-resistant Cryptosporidium or poorly maintained pools and spas. In a survey of over 13,000 public hot tubs/spas, about 20 percent had improper disinfectant concentrations. Home pools are subject to similar concerns.
In addition to microbes and algae, macro-organisms (such as mosquitoes) may take up residence in the standing water of stock-tank pools. Physical hazards may exist too, such as hot metal edges. Some creative owners have fashioned foam pool noodles to cover tank edges and create comfortable headrests.
Water quality maintenance
Maintaining the quality of treated recreational water is extremely important for the health of swimmers and to prevent microbes and algae from growing in the pool. Installing a pump to keep water circulating will discourage the accumulation of mosquito larvae and algal slime. The primary treatment methods are chemical disinfection and filtration. Filters may be purchased that are capable of removing chlorine-resistant protozoan and many bacterial pathogens, but viruses are too small to be efficiently removed by filtration. Chlorine or other sanitizers are necessary to kill harmful bacteria and viruses. Keeping the proper balance of essential chemicals and maintaining effective filtration, however, can be very difficult, particularly in smaller water volumes and during frequent use. Rain, debris (leaves and dust) and people (skin cells and oils) rapidly create chlorine demand in the water, depleting levels of chemicals designed to keep pools clean. If a small volume of water is contaminated by an infected individual, others can be quickly exposed, and before the water filter has a chance to do its job.
Chlorine tablets are widely available at pool supply stores and floating dispensers can provide consistent treatment. Concentrations of at least one ppm of free chlorine are recommended. At this level, most bacteria and viruses are inactivated within minutes, however, Cryptosporidium could still survive for a week at this concentration. Therefore, a combination of filtration and chemical disinfection is needed for optimal recreational water treatment. Even with routine treatment, stock-tank water should be drained and refilled periodically, maybe even monthly or more frequently, depending on how often it is used. Don’t wait until the water looks cloudy! Scrub any biofilm off the interior tank surface with a mild soap and brush to prevent any slime build-up.
With proper care and maintenance, stock-tank pools can provide a great recreational water experience. Studies have shown that leisure swimmers consume hundreds of milliliters of water per swim and that splashes to the face correlated with the highest level of water ingestion.5 Children are at the greatest risk of infection due to their generally rougher pool play events that lead to splashing and increased water ingestion.6 They are also more likely to have a lack of healthy swimming habits, such as showering before swimming or handwashing compliance after using the restroom.7 Carefully monitoring contamination potentials and making sure pool water is properly treated before every swim is critical for good health and safe swimming.
- Murtaugh T. 5 of the Biggest problems People Have with Stock Tank Pools and How to Prevent Them. Country Living. https://www.countryliving.com/life/news/a44181/stock-tank-pool-problems/. Published 2020. Accessed July 12, 2020.
- Marciano-Cabral F, MacLean R, Mensah A, LaPat-Polasko L. Identification of Naegleria fowleri in Domestic Water Sources by Nested PCR. Appl Environ Microbiol. 2003;69(10):5864-5869. doi:10.1128/AEM.69.10.5864-5869.2003
- Sifuentes LY, Choate BL, Gerba CP, Bright KR. The occurrence of Naegleria fowleri in recreational waters in Arizona. J Environ Sci Heal–Part A Toxic/Hazardous Subst Environ Eng. 2014;49(11). doi:10.1080/10934529.2014.910342
- Hlavsa MC, Cikesh BL, Roberts VA, et al. Outbreaks Associated with Treated Recreational Water–United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018;67(19):547-551. doi:10.15585/mmwr.mm6719a3
- Suppes LM, Abrell L, Dufour AP, Reynolds KA. Assessment of swimmer behaviors on pool water ingestion. J Water Health. 2014;12(2):269-279. doi:10.2166/wh.2013.123
- Suppes LM, Canales RA, Gerba CP, Reynolds KA. Cryptosporidium risk from swimming pool exposures. Int J Hyg Environ Health. 2016;219(8):915-919. doi:10.1016/j.ijheh.2016.07.001
- Castor ML, Beach MJ. Reducing illness transmission from disinfected recreational water venues: Swimming, diarrhea and the emergence of a new public health concern. Pediatr Infect Dis J. 2004;23(9):866-870. doi:10.1097/01.inf.0000138081.84891.30
About the author
Dr. Kelly A. Reynolds is a University of Arizona Professor at the College of Public Health; Chair of Community, Environment and Policy; Program Director of Environmental Health Sciences and Director of Environment, Exposure Science and Risk Assessment Center (ESRAC). She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at firstname.lastname@example.org