Water can dissolve more substances than any other liquid. It is essentially nonionic or neutral. While alkaline and acid solvents can only remove compounds of the same pH, water — being neutral — can dissolve solutions and compounds of any pH. Water is the body’s way of purifying itself. Our bodies are 73 percent water, and more than 80 percent of our blood and brain are water. In addition, as a solvent, water washes through our kidneys and takes toxins out of our bodies. Simply put without water, we would be poisoned and we would cease to exist.
Water is important in all stages of medical device reprocessing. In fact, water is required for each step in the decontamination process, from soaking to manual or automated cleaning to rinsing, including the final disinfecting rinse. Furthermore, even concentrated instrument cleaners are composed primarily of water, the solvent for all chemicals in the solution.
Water that is safe to drink may not be acceptable for reprocessing or for sterilizing surgical devices. Water quality varies from place to place and according to the season of the year. Most public water systems include additives such as chlorine, dissolved salts and sometimes significant naturally occurring mineral content, and even organic contaminants, bacteria and endotoxins. Depending on water hardness and temperature, fresh water used can lead to the formation of hard water deposits, a layer of lime or scale that is difficult to dissolve. And, corrosion may occur under these deposits. When water evaporates, some substances can remain as visible mineral residues. Furthermore, any procedure requiring water in its operation presents a potential hazard. This is particularly true if water is not continually changed or sinks cleaned after use. Water supports the growth of Gram-negative bacteria. Calcium, magnesium and pH can stain instruments and inactivate disinfectants. That is why distilled, reverse osmosis or deionized water is recommended for use dilution with all concentrated instrument cleaners and approved disinfectants.
Tap water is contaminated with toxic heavy metals, synthetic organic chemicals, chlorine, biological parasites and thousands of other harmful contaminants. According to a research group, “EPA reports show that U.S. water supplies contain over 2,300 cancer causing chemicals.”1 In addition, all the chemicals we use will ultimately show up in our tap water. There is no new water; our planet keeps recycling the same water. Furthermore, water treatment facilities are not designed to remove organic chemicals and toxic heavy metals, like lead.
Water treatment today is similar to practices 100 years ago, as water flows through sand beds to remove visible particles and then bleach or chlorine is added to kill bacteria. Furthermore, even treated water can contribute to the problem. In softened water, the hard water ions are replaced by sodium salts, but this does not reduce the substances in the water and alkalinity can greatly increase as a function of exposure and temperature. When a thermal disinfecting rinse is used as the final rinse, metals such as aluminum might be subject to attack. Deionized water removes charged ions, but has no capacity for removal of non charged ions including bacteria and bacterial endotoxins. Polymeric materials used for instrument processing including plastic trays can absorb endotoxins. DI water treatment requires close monitoring for when its capacity is exceeded the treated water can have dangerously high levels of previously removed contaminants. Ultra filtration or UV may be required after deionized water treatment.
Water can also damage stainless steel instruments. Stainless instruments are susceptible to pitting when there is an increase in the chloride content in the water, when there is an increase in temperature, with decreasing pH values, increased exposure times, insufficient drying and concentration of chloride from dry residues to instrument surfaces after evaporation.
In recent years, there has been growing awareness about the importance of water in the decontamination of surgical devices and the harmful effects of even minute quantities of contaminants on patients. This is of particular concern because certain medical devices may introduce contaminants directly into the body that are normally protected by skin and mucous membranes. Metals, organic compounds, microorganisms and pyrogens can lead to adverse reactions. Furthermore patients are particularly susceptible when surgical instruments bypass the body’s defenses.
Water fulfills a variety of functions in the decontamination process. First, it dissolves cleaners and other treatment agents. It provides both mechanical action as well as transfer of heat to the surface of items to be cleaned. Also, it dissolves soluble dirt and impurities and it flushes away instrument chemistries and soil. In addition, water is the source for steam used to sterilize most surgical devices and patient-care items.
Water quality is an important consideration in the decontamination of surgical instruments. In Europe, HTM 2030 provides guidance on the choice, specification, purchase and validation as well as maintenance of automated washers and provides recommendations for purified water standards and system designs as well as steam quality. The standard states, “The sterilization steam must be free from impurities and should neither impair the sterilization process nor damage the sterilizer or the items to be sterilized.”
The use of feed water or steam containing substances in excess of the stated values in the table below can reduce the service life of the sterilizer and in Europe may also void the manufacturer’s warranty. As a result there are specific tolerances relating to the quality of the boiler feed water as follows: