The water flowing from an outdoor spigot is initially the same highly regulated municipal water supplied to the rest of the home. However, once this potable water enters a garden hose, its quality is immediately subject to change. The difference between tap water and hose water lies in the materials of the hose and the environmental conditions under which it is used.
The Source: Understanding Tap Water Quality
The water entering an outdoor spigot begins as a product of extensive municipal treatment systems. Suppliers follow strict legal requirements, such as the National Primary Drinking Water Regulations, which mandate filtration and disinfection processes. These regulations limit levels for over 90 contaminants, ensuring the water is safe for consumption upon delivery.
This regulated water is maintained with a residual disinfectant, like chlorine, as it travels through the main distribution pipes. The quality at the point where it exits the wall remains consistent with the household’s supply. However, the outdoor spigot is often not manufactured to the same material safety standards as indoor kitchen faucets designed for drinking water contact.
Chemical Concerns from Hose Materials
The most pronounced difference in water quality occurs when the water contacts the hose material, causing chemical leaching. Standard garden hoses are frequently constructed from polyvinyl chloride (PVC), which requires plasticizing agents for flexibility. These plasticizers often include phthalates, a group of chemicals that can migrate into the water, with some studies detecting levels exceeding federal drinking water standards.
Hose components, including the plastic and brass fittings, can also introduce heavy metals. Studies have shown that lead can be present in the water from certain hoses, sometimes at concentrations that surpass the Environmental Protection Agency’s action level of 15 parts per billion for drinking water. This lead contamination can originate from the brass connectors or be found within the PVC material itself, especially in hoses made with recycled electronic waste vinyl.
Another chemical found to leach from plastic hoses is Bisphenol A (BPA), which has been measured at high concentrations in water that has sat inside a hose. This chemical migration is concerning because garden hoses are not subject to the same strict material safety standards as certified indoor plumbing or specialized “drinking water safe” hoses. Even some hoses labeled as safe for drinking water have been found to contain detectable levels of phthalates.
Environmental Factors and Stagnant Water
Beyond material composition, environmental conditions create a separate contamination risk within the hose. When water remains stagnant inside a coiled hose for extended periods, the disinfectant residual dissipates, allowing microorganisms to multiply. The dark color and location of a hose left in direct sunlight can cause the internal water temperature to rise significantly, often reaching the ideal range of 20°C to 42°C for bacterial growth.
This warm, stagnant environment is conducive to the growth of Legionella bacteria, which can colonize the inner surface of the hose in a protective layer called biofilm. When the hose is used, especially with a spray nozzle that creates a fine mist or aerosol, these bacteria can be released and inhaled. Cases of Legionnaires’ disease have been linked to the inhalation of water droplets from contaminated garden hoses.
High temperatures also accelerate the chemical leaching process from the hose materials into the standing water. To mitigate these risks, it is recommended to drain and store hoses out of the sun. Always flush the line for a minute or two until the water runs cool before use, as this removes the water most likely to contain accumulated contaminants.