Posts Tagged ‘soft water’

February 7, 2013

Enjoy Des Moines’ Soft Water? Thank the Federation of Women’s Clubs of 1927

Filter Building interiorIn 1927, the Des Moines Federation of Women’s Clubs petitioned to the Board of Water Works Trustees to install a municipal water softening plant to save customers money spent on soap and wear and tear on clothes. For the next 20 years there were arguments for and against construction of such a facility and then World War II delayed progress of this project until 1947.

A lengthy feature article titled “City to Enjoy Soft Water in Two Years” appeared in The Des Moines Register in November 1947.  It described the advantages of soft water and the method of treatment that would be used, and mentioned that cost of the operation of the plant might have to be financed through a raise in water rates.  The state health department engineer was quoted as saying the usual experience is that the added cost of soft water is equaled by the saving in soap alone.  He also mentioned additional savings, such as longer life of boilers and water heaters.

In December 1949, the filter and lime softening plant went into operation. It consisted of two underground basins, each with a four million gallon capacity, and the filter building which housed the laboratory, chemical feed operations, and eight filters. The filters resemble small swimming pools, each of which contains 100 tons of gravel and 130 tons of sand and holds approximately 50,000 gallons of water.

In the underground basins, lime is mixed with water to remove minerals and kill bacteria. Then the water was pumped to the filters, where it was cleaned by passing through layers of gravel and sand.

In 1958, the capacity of the filter plant doubled when two lime softening basins and eight filters were added.

The filter and lime softening processes are vital to treating the public water supply and are still being used today.

Posted by: Pat Ripley No Comments
Labels: , , , , , Posted in About Us, History, Water Treatment August 16, 2011

The Soft and Hard Side of Your Water

When it comes to CaCO3, otherwise known as limestone, some like it hard and some like it soft.  Water hardness is the amount of soap precipitating minerals in the water. The harder the water, the less effective soap will be.

Since 1948, lime softening has been a part of the treatment process at Des Moines Water Works.  Powdered lime is mixed with water, forming a slurry, or thick liquid.  This mixture is then fed into the four lime softening basins.  As the water passes through the softening process, the lime slurry attaches to excess minerals in the water forming a lime floc.  The limestone floc then settles to the bottom of the basins as by-product.

This process is beneficial for several reasons. First, removing the minerals helps lessen the hardness of the water, which allows detergents and soaps to clean better.  Lime softening also kills harmful germs and bacteria, and causes a thin protective coating to form on the inside of pipes. This coating inhibits leaching of lead from older pipes into the drinking water supply.

DMWW strives to maintain the total hardness of drinking water to less than 150 mg/L.  This equates to 8.76 grains of hardness on a water softener setting.  Individuals who prefer softer water may consider purchasing and installing a water softening unit in their home.  However, excessively soft water is very corrosive to your pipes.

There is no adverse health effect associated with hard or soft water – it’s just a matter of personal preference.  You can get daily water hardness readings from DMWW’s lab reports.

Posted by: Laura Sarcone 2 Comments
Labels: , , , , , , Posted in Water Quality, Water Treatment