Did you know that minerals and contaminants commonly present in city water supplies make tap water a poor choice for use in dental bottles and delivery systems? Whether your delivery unit is plumbed directly to a water supply or uses an independent bottle system, using tap water in dental unit waterlines isn’t ideal.
Let’s examine these characteristics one at a time.
Although city water is mechanically filtered at the municipal treatment plant, it’s then pumped through miles of piping. Its journey to its various points of use can introduce all manners of particulate and debris—suspended solids—from cracks in old pipes, construction areas, fire hydrant use and more. Water that leaves a treatment plant with virtually no suspended solids can have very high TSS levels by the time it reaches a dental office!
Physical filtration removes suspended solids from water, making subsequent treatment processes more efficient and effective. That’s why using some form of physical filtration at the water-entry point of a building can be so beneficial. Basic, whole-office filters are often placed on a main water line in an equipment room, alongside a solenoid shutoff valve.
Further, using a submicron-grade filter prior to feeding water to a dental delivery unit can be extremely helpful. Not only do submicron physical filters remove the vast majority of microbial contaminants, but they also protect dental delivery system components from even very tiny suspended solids that can clog and damage equipment.
Dental delivery units are comprised of a variety of materials, frequently including aluminum, nickel, zinc, copper, plastic and rubber. High levels of dissolved solids (TDS) in the water can interact with these materials and greatly increase the chances of various chemical reactions, calcification, discoloration, and the buildup of valve-clogging deposits. So, in general, lower-TDS water is better for delivery units—unless the TDS gets too low!
Water in its purest state—containing zero TDS—is known as the “universal solvent” and can dissolve various materials used in the construction of dental delivery units over time. That’s why we never recommend using distilled (or deionized) zero-TDS water in delivery systems. The bottom line is that TDS levels should not be too high, or too close to zero.
Special processes like reverse-osmosis purification can remove 90-98% of the dissolved solids in water (depending on water pressure), leaving only a small amount of TDS behind, which is ideal. But while beneficial, this specialized filtration isn’t always necessary for the dental operatory. Average TDS levels in municipal water supplies vary greatly by geographic region, but the (US) national average is in the ballpark of 300 parts per million (ppm), which can be just fine for the delivery unit—depending on which solids are dissolved in the water.
In summary, having low TDS is generally better—all the way down to around 005 ppm, below which you’d need to be concerned about the water “attacking” and dissolving certain components of the dental delivery system over time.
As we’ve discussed in another blog entry, even sterile water can quickly become contaminated in dental delivery units. That said, in this blog entry we’re talking about the water that goes into the delivery system.
The good news for practices using city water is that municipally treated water typically has very low counts of viable colony-forming units (CFUs) of microorganisms, due primarily to chlorination. However, practices in rural areas that use well water frequently have higher levels of microbial contamination, which makes the challenge of managing growth in the waterlines to CDC and ADA-recommended output levels of <500 CFU/ mL much more difficult.
Remember the old adage: garbage in, garbage out. Whether your delivery unit is plumbed directly to a source water supply line or uses an independent bottle system, you want the water fed to your dental delivery system to be as free from microbial contamination as possible.
Hard water has high mineral content that’s typically acquired when groundwater percolates through deposits of limestone and chalk, which consist (mostly) of calcium and magnesium carbonates. Because these carbonates dissolve in the water, hardness and TDS are frequently correlated. However, it’s also possible to have low hardness (soft water) with high TDS, so these factors should be separate considerations.
Water hardness is commonly measured in “grains” per gallon (gpg) or milligrams per liter (mg/L). As a general rule, water hardness in excess of five grains per gallon should be “softened” with separate treatment prior to using in the delivery system. Otherwise, this hard water can create deposits and “scale” on the inside of the delivery unit, which can not only block the water flow, but also provide an enhanced breeding ground for microorganisms.
Softening hard water can actually benefit the entire office by extending the life of pipes, hot water heaters, and other appliances. In summary, the lower the hardness, the better.
You might remember from your high school Chemistry class that pH is a numeric scale used to specify the acidity or basicity (alkalinity) of an aqueous solution—in our case, water. Pure, zero-TDS water is a perfectly neutral 7. Water with pH less than 7 is acidic, and with pH greater than 7 is basic.
Ideally, the water used in delivery units should be perfectly neutral (7.0). Water that is too acidic eats away at materials in the dental delivery system over time—much like zero-TDS water—and water that is much too alkaline can also create problems. Typically, city water is neutral to alkaline—say, between 6.5-8.5—although a more narrow range of 6.8-8.0 is preferable.
Note: because pH is measured on a logarithmic scale, a change in pH of 1.0 means the water is 10 times more acidic or basic! All of these factors—including pH—can be gauged with a simple water test kit, and are sometimes available upon request from your local municipality, if you’re using city water.
If you have “input water” from the city that’s free from microbial contamination with low TDS, low hardness, and a relatively neutral pH, you’ve got the best starting point for the dental delivery system. Specialized filtration systems can protect dental equipment and remove contamination, as well as remove dissolved solids for even better dental water quality.
Regardless of the quality of "input water" or filtration systems used, staff members must perform the required daily flushing protocols and regular waterline maintenance to ensure the best “output water” possible, too.