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Water Hardness

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What is Water Hardness?

Water hardness is one of the most common water quality concerns reported by consumers in the United States. Water that is considered to be “hard” is high in dissolved minerals, specifically calcium and magnesium. As the concentration of the dissolved minerals increase, the water becomes harder.

The two most common units of measurement for hardness are grains per gallon and milligrams per liter. Some appliances, such as dishwashers, have a setting to adjust for the hardness of the water. Usually the hardness setting for these appliances is in grains per gallon.

In grains per gallon, water hardness is classified as follows:

  • Less than 4 grains per gallon is considered to be soft
  • 4 to 7 grains per gallon is considered to be moderately-hard
  • 7 to 10 grains per gallon is hard
  • greater than 10 grains per gallon is very hard


Is Hard Water Safe to Drink?

Yes, hard water is safe to drink and to use for cooking and cleaning and is not a health risk. The California Department of Public Health and the US Environmental Protection Agency do not consider hard water a health issue and there are no standards or limits set for hardness.

Why Was there an Increase in Water Hardness in Glendale

Glendale gets approximately 70% of its water supply from the Metropolitan Water District of Southern California (MWD). MWD has two sources for water, the Colorado River and State Water Project from northern California. MWD treats the imported water at a number of treatment plants in the region. Over the last year, water supplied to the City by MWD came primarily from the Weymouth Treatment Plant. Due to water supply challenges over the past year, the source of water at the Weymouth Treatment Plant has been exclusively Colorado River water.

The Colorado River water supply is classified as very hard water. In previous years MWD was able to blend the moderately hard water imported from northern California with Colorado River water before treatment at Weymouth and in turn lower the hardness of the Colorado River water delivered to Glendale. This past year, State Water Project supplies have been greatly reduced due to drought and environmental regulation. With no water from northern California to blend with the hard Colorado River water at Weymouth, we have been receiving much harder water from MWD.

In the past, Glendale occasionally received water from MWD’s Jensen Treatment Plant. However, this plant is largely dependent on State Water Project water, and due to restricted supplies, no water from Jensen has been available to Glendale.

Glendale also has local water supplies in the form of groundwater wells. These wells provide approximately 30% of Glendale’s water supply. Generally, Glendale well water is harder than the Colorado River water. Well water is treated and blended with MWD water. While hardness levels can vary throughout Glendale due to blending with local groundwater supplies, water hardness in Glendale averaged over 12 grains per gallon during 2008 and thus would be considered very hard water.

What are Signs of Hard Water in My Home?

Hard water can be a nuisance in many ways. You may notice an accumulation of white/chalky deposits on items such as plumbing, tubs, sinks, pots and pans. Other things you may notice include:

  • increased difficulty in cleaning and laundering tasks,
  • decreased efficiency of water heaters,
  • white spots on glassware,
  • white spots on your car after washing,
  • soap scum on bathtubs, shower tiles, and basins, and
  • it is more difficult to remove soap when washing or bathing,
  • accumulation of hard, cream colored deposits around fixtures and inside pipes.

Is There Anything I Can Do to Remove Hardness?

Removal of calcium and magnesium from water can turn hard water into soft water. The two most common processes to remove calcium and magnesium from the water are (1) reverse osmosis filtration, and (2) ion exchange. Reverse osmosis filtration units can handle only small volumes of water and are usually installed at the kitchen sink. Ion exchange units can treat large volumes of water and are typically installed to treat either all of the water entering the residence or just the hot water supply.

Over time mineral deposits will accumulate in the plumbing system from a hard water supply. It is important to note that installing a new water softener on a house with an older plumbing system which has not previously been softened may cause these mineral deposits from the pipes to break loose. These small bits of minerals, in time, can clog inlet screens to dish and clothes washing machines, showerheads, and filters or water aerators at the ends of faucets.

An alternative to a system softener or hot water softener is to use liquid and powdered softeners. These can be added to dishwashers or laundry machines on a per load basis to soften the water, reduce the amount of soap or detergent, and reduce spotting on dishware.

The following are the advantages and disadvantages of using softened water systems:


  • Smaller amount of dish washing and laundry detergent is needed.
  • Reduced mineral deposits in plumbing, water heaters, and on pots and pans.
  • Fewer water spots on air-dried dishes and glassware.
  • Hair and skin will often feel softer after bathing or washing.

Disadvantages of Ion Exchange Systems with salt supplies

  • In some ion exchange systems, there is an increase in sodium content in the water (some Glendale residents may be on a sodium restricted diet from their doctor),
  • Require a supply of salt crystals which can be costly over time,
  • A salt brine disposal line must be run to a sewer drain, which in turn raises the salinity of the waste water and can cause difficulties in treatment and disposal processes,
  • Softened water tends to be more corrosive and could decrease the life of internal plumbing.


  • Hard water supplied by the City does not have to be softened to make it safe or usable.
  • Hard water is safe for drinking, cooking, and other household uses.
  • Glendale residents need to weigh the advantages and disadvantages of having hard and/or soft water. Installation of softeners entails additional cost and will require regular maintenance depending on the type of equipment installed.
  • For a list of state certified water treatment devices, please go to the State Water Resources Control Board's website.