The Tool Barn


A Guide to Water Softeners

Calcium and magnesium cause hard water, and high levels can precipitate and clog pipes. The best way to soften water in household water systems is to use a water softener unit connected into the water supply line. You may want to consider installing a separate faucet for unsoftened water for drinking and cooking. Water softening units also remove iron.

General Description
The most common way to soften household water is to use a cation-exchange water softener. Softeners may also be safely used to remove up to about 5 milligrams per liter of dissolved iron if the water softener is rated for that amount of iron removal. Softeners are automatic, semi-automatic, or manual. Each type is available in several sizes and is rated on the amount of hardness it can remove before regeneration is necessary.

Limitations
Using a softener to remove iron in naturally soft water is not advised; a green-sand filter is a better method.

Maintenance
When the resin is filled to capacity, it must be recharged. Fully automatic softeners regenerate on a preset schedule and return to service automatically. Regeneration is usually started by a time clock; some units are started by water use meters or hardness detectors.

Semi-automatic softeners have automatic controls for everything except for the start of regeneration. Manual units require manual operation of one or more valves to control backwashing, brining and rinsing.

In many areas, there are companies that provide a water softening service. For a monthly fee the company installs a softener unit and replaces It periodically with a freshly charged unit.

Need for Iron Removal

Iron in the ferric form and manganese will stain clothes and plumbing fixtures. Ferrous iron is in the dissolved form and cannot be seen in water. When water containing ferrous iron is exposed to air, the iron oxidizes and ferric iron is formed. Ferric iron usually appears as rust colored particles floating in the water.

Water with a high iron or manganese content is not considered a health problem, but it can be very objectionable in taste, odor or appearance. Iron bacteria are nuisance organisms often associated with soluble iron in water. Because they cause a slime buildup they can be quite objectionable. Calcium is an essential nutrient for this bacteria. The presence of iron bacteria is indicated by a gelatinous slime on the inside wall of the toilet flush tank and gelatinous "rusty slugs" being discharged at the tap. High dosages (200 to 500 milligrams per liter) of chlorine (known as shock chlorination or disinfection) are required to control iron bacteria. Shock chlorination must include the well and system.

General Description

Four types of iron-removal equipment are available:

Iron Filters. Iron filters are only useful for removal of ferrous iron and manganese; ferric iron will plug them. They appear similar to water softeners but contain a bed of natural or synthetic manganese green sand. Manganese dioxide oxidizes iron and manganese and the oxidized particles are then filtered out in the lower part of the bed.

Water softeners. All water softeners will remove iron; the rating for iron depends on whether the regeneration will remove the iron from the zeolite or not. Water softeners contain a zeolite mineral that will remove soluble iron on an ion-exchange basis (the same way calcium and magnesium are removed in water softening). The slime produced by iron bacteria will clog the zeolite and reduce its effectiveness.

Polyphosphate feeders. These units contain a phosphate compound which coats the soluble iron and prevents its oxidation when the water is exposed to air. The compound is not effective against iron that has already oxidized. When some waters are heated, the raised temperature will reduce the effectiveness of the polyphosphate so that oxidized iron will accumulate in the water heater. (Polyphosphate is only effective in cold water. Heating the water will release the iron.) The heated water will be rusty and unsatisfactory for home uses.

Chlorination and filter. Chlorination followed by filtration through a sand filter can remove any quantity of iron in any form. The chlorine oxidizes and precipitates the iron and the filter strains out the particles. Carbon filtration may be required to remove excess chlorine residue. This method also destroys iron bacteria. When the bacteria cannot be permanently eliminated by shock chlorination, continuous chlorination is required.

Neutralizers: Primary Use This system treats corrosive (acidic) water. Alkalinity and pH are increased through processing.

General Description

Passing the water through granular calcite (marble, calcium carbonate or lime) is the most common method of home treatment. A mix of calcite and magnesium oxide also is used. if the water is very acidic or if a high flow rate is needed, a system to chemically feed soda ash,
sodium carbonate or caustic soda (sodium hydroxide) may be necessary. These systems increase the sodium content of water, whereas using calcite or lime increases calcium.

Disinfection Methods

Chlorination - Both municipal systems and households can disinfect water by adding chlorine.
Household systems commonly use household bleach. Chlorination does not remove nitrates or other chemicals, but may oxidize organics and some minerals such as iron. Chemical metering devices must be maintained carefully. Using a carbon filter after chlorination will remove any excess chlorine and chlorinated chemicals that form.

Other Methods

Other methods of disinfecting water include boiling, pasteurizing, treating with ultraviolet light, and treating with ozone. These methods are usually less practical than chlorination or not readily available. Note that sterilization (boiling water vigorously for at least two minutes) kills all organisms. Disinfection reduces the concentration of organisms to safe levels. Devices to kill or remove bacteria or viruses are termed purifiers. Chlorination, distillation, or boiling for 15 minutes are the usual methods used to purify water for household use.

Disinfection by ozonation or ultraviolet light methods are replacing chlorination in some water
treatment plants, but are not yet readily available for home use.

Some filtration units with silver-coated activated charcoal blocks are being sold for removal or killing of bacteria. Before purchasing such a unit, evaluate it carefully and check for sufficient test data and certification to assure its effectiveness.

The above information comes from North Dakota State University Extension bulletin E-430, Household Water Treatment.

Figures: Automatic Water Softener - 23K, Backwash Filter - 20K

Please read the MSU disclaimer for important information about using our site.

Reprinted from The Michigan State University Extension. - Michigan State University Extension Home Page


Printer friendly page


E-mail this page to a friend