Commercial Water Hardness

Some residents, businesses and industries are concerned about the hardness of the Cambridge tap water.

1 What causes hardness?

The hardness of water comes from dissolved minerals, most predominately calcium and magnesium. As water moves through soil and rock in the watershed, it dissolves these minerals.

2 Does hardness make the water unsafe?

From a health standpoint, the minerals in water that cause hardness have no adverse effects, and are, in fact, essential daily nutrients. Both calcium and magnesium are essential minerals and beneficial to human health in several respects. It is minerals that give water the refreshing flavor that many people find desirable. Water without minerals, such as distilled water, can taste “flat”.

The Environmental Protection Agency (EPA) has not established a standard for water hardness.

3 What is the level of hardness in Cambridge tap water?

Cambridge water is considered slightly hard. Cambridge water has a hardness ranging from about 50 to 70 milligrams per liter (mg/L), also called parts per million (ppm). Another common unit of measure for hardness is “grains per gallon” or “GPG” for short. One “GPG” is equal to about 17 mg/L. So, Cambridge water hardness measured in grains per gallon ranges from 3 to 4 GPG.

The level of hardness in water is classified according to the following chart.
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4 How does Cambridge water compare to other cities and towns?

Almost all of Massachusetts has soft to slightly hard drinking water. The MWRA supplies drinking water to 42 communities in greater Boston and the Metro West area. MWRA water comes from reservoirs in central and western Massachusetts and is considered soft, with a hardness of about 15-20 ppm.

Some communities in Massachusetts obtain their drinking water from groundwater wells, or a combination of groundwater wells and surface water reservoirs. Groundwater generally has a higher hardness level than surface water. The nature of the watershed also affects the hardness level of the water. Here is a comparison of the hardness level in the drinking water for some cities and towns:

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Hard water is very common in most of the United States, affecting more than 85% of the country. Because most of the drinking water supplied in the U.S. comes from groundwater, it travels through rock and soil, picking up minerals along the way.

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5 What are the effects of hardness?

The calcium and magnesium minerals in hard water can build up on contact surfaces, possibly plug pipes and clog water heaters, and decrease the effectiveness of soaps and detergents. Hard water can make it difficult to produce a lather (suds) when washing. Hard water often produces a noticeable deposit on plumbing fixtures such as faucets and showerheads, leaves a film on glasses, and causes “bathtub ring”. These minerals can also deposit as a scale in heated water applications, and coat the surfaces and reduce the efficiency of water tanks and heat exchangers.

6 How can hardness be reduced?

The Cambridge tap water is slightly hard and will not cause major scaling or laundering issues. However, if you feel that you would benefit from lower hardness levels, you can install a water softener on your water supply line. For most households in Cambridge, the decision to install a water softening unit is a matter of personal preference and not necessity.

The most common type of water softener used in homes is an ion exchange unit. The water passes through a bed of “beads” that are supersaturated with sodium. The water becomes softened when the sodium from the beads “exchanges” with the calcium and magnesium in the water. The calcium and magnesium attach to the beads, while the sodium from the beads is released into the water. Eventually, the beads will become clogged and saturated with calcium and magnesium, and they must be regenerated. Regeneration is done through a process called “backwashing” using a salt solution.

While the City of Cambridge cannot make recommendations as to the type or brand of softener, we do suggest that if you are interested in purchasing a softening system that you look for equipment that carries the seal from the Water Quality Association (WQA), National Sanitation Foundation (NSF), or Underwriters Laboratories, Inc. (UL). A seal from any of these organizations indicates that the equipment has been independently tested to industry performance standards. These organizations also have an on-line database of the equipment that has been tested and certified. For example, the NSF listings can be obtained here:

For commercial and industrial applications, the type of softening system should be selected by a licensed professional engineer who can evaluate the specific needs of the facility. Please see section 9.2 and 9.3. for more information.

7 What concerns should I be aware of when considering a water softener?

All incoming water may not need to be softened and you may wish to soften only the water supplied to your hot water tank or heat exchanger. Softening water using an ion exchange unit will increase the sodium level of the water and may present a concern for people on low sodium diets. If you soften Cambridge tap water, the sodium level will increase by 6 to 7 milligrams in every 8-ounce glass of water.

Softened water can also increase the corrosiveness of the water and the potential for metal leaching from pipes, solder, and plumbing fixtures.

About 50 gallons of water will be used (wasted) each time the softening unit is regenerated.

All water softeners need to be properly operated and maintained. Regular maintenance includes replenishing the brine solution, periodic cleaning and disinfecting to eliminate the growth of bacteria, and possibly needing to unclog the bed of “beads.”

8 Are there options to address hardness besides installing a water softener?

If you feel that hardness in your water is a concern, the following practices can be beneficial:

- Keep hot water temperature less than 140 degrees Fahrenheit (F)

- Periodically inspect, clean and flush hot water tanks. Please see section 9.4 for more information

- Use a laundry additive such as Borax or Washing Soda, or purchase a laundry detergent that comes with a water softening agent added (e.g., Calgon)

- Use a dishwasher rinse aid

- Use white vinegar on tiles, glass and faucets to help remove mineral deposits

9 For more information…

The sections below provide more information specific to each category of water use in Cambridge.

9.1 Homeowners and Residents

If you are considering purchasing a home water treatment system, the first step is to identify a unit that will address your specific water quality concern. Water treatment systems are certified by three organizations, all who are accredited by the American National Standards Institute (ANSI).

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The certification of home water treatment systems involves several aspects:

- Verifying the contaminant reduction performance claim made by the manufacturer

- Evaluation of the unit including its materials and structural integrity

- Review of the product labels and sales literature

The three organizations can assist in selecting a system/unit that meets your needs.

There are drinking water standards for health concerns (such as removal of specific contaminants) and for aesthetic concerns (such as improving taste or appearance of water). Certification from these organizations will be tied to one or both drinking water standards.

9.2 Building Managers

Each building or facility has specific requirements that should be evaluated by a qualified licensed professional engineer with experience in design of boiler systems, including any requirements for water conditioning.

One place to start is to look for a member of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) or . You can also check a professional engineering or The Massachusetts Board of Registration of Professional Engineers licenses engineers to practice in the state by specialty discipline ( The state provides a license “look-up” service on its website for professionals including engineers, plumbers and gas fitters at

9.3 Contractors/Plumbers

The City of Cambridge’s Inspectional Services Department (ISD) enforces all laws and related City Ordinances pertaining to the Massachusetts State Building Code and certain articles of the State Sanitary Code including Plumbing and Gas, and Mechanical Codes.

The City has an on-line system when applying for plumbing permits or mechanical permits for furnaces and boilers. These permits are issued to Massachusetts licensed plumbers and gasfitters in accordance with Massachusetts General Law (MGL) 142-13 in the case of plumbing and gas permits.


Have the Sacrificial Anode Inspected

One of the most important factors in how long a water heater will last is the condition of the sacrificial anode, which protects the tank from corrosion. A sacrificial anode is a rod that is screwed into the top of the water tank. This rod is made of either aluminum or magnesium formed around a steel core wire.

The life of the sacrificial anode depends on the quality of the water, how much use the tank gets, the water temperature, and the how well the tank is constructed. Have your plumber periodically inspect the sacrificial anode, and they can advise you if it should be replaced when it has become partially deteriorated. If you wait until it is fully deteriorated, replacing it may be too late.

Annual Tank Flushing and Cleaning

Good practice is to have your plumber flush and clean out your water heater tank annually. The links below can give you an idea of what is involved so you can know what to expect and what questions to ask your plumber to make sure that the work is thorough.

Water heater maintenance tips can be found at: