What Is the Hardness

How "hard" is the water in Cambridge?

Water hardness refers to the mineral content of water, commonly calcium and magnesium. CWD's water is "slightly hard" and varies only slightly throughout the city. Hardness also varies slightly by seasons of the year.  When using dishwashers, you may notice a slight increase in "spotting" on glassware, flatware or white residue in kitchenware and showers. Using a high quality dishwasher detergent with a rinse agent will solve this problem. This residue consists mainly of calcium carbonate, the same ingredient found in anti-acid products and not a known health risk. The hardness of the city's tap water is typically around 40 to 60 parts per million or 3 to 4 grains per gallon.

What is the white residue I sometimes find on cookware, in the shower and even in ice cubes?

White residue is commonly found in showers and kitchenware as the result of dissolved minerals found in water, such as calcium and magnesium. Mineral particles can also be visible in ice cubes made with tap water. These minerals are not a risk to human health but can build up on surfaces over time. Commercial products are available to remove white residue caused by minerals in water.

All of the strainers in my faucets are clogging with white particles. What could this be?

Aerators are strainers that attach to your faucet or shower head and break up the flow of water as it leaves your tap. Aerator screens can collect particles found in water and should be routinely cleaned throughout the year and replaced once a year. Particle build up is often white and comes from a variety of sources.

The most common source of build up in aerators is from the hot water heater. The hot water heater dip tube is made of a nontoxic plastic material called polypropylene. This plastic can break apart or disintegrate and travel in hot water to your faucet, eventually collecting in the aerator.

Dissolved calcium is naturally found in our drinking water and can naturally change to calcium carbonate in hot water heaters. Over time, calcium carbonate may accumulate at the bottom of the hot water heater and collect in your aerators.

To determine whether the material is calcium carbonate or polypropylene, place the material in a small amount of distilled vinegar. If the particle begins to "bubble" within a few minutes or is mostly dissolved within 24 hours, it is likely calcium carbonate. If no bubbling occurs or the particle does not dissolve, it is likely polypropylene.

If you are experiencing a calcium carbonate problem, we recommend flushing the hot water heater. Contact a plumber or download instructions for draining your hot water heater.

If you are experiencing a polypropylene problem, call the manufacturer of your hot water heater.

For additional information, contact the Cambridge Water Laboratory at 617-349-4780.