Glenda M. Herman
Extension Housing Specialist
Gregory D. Jennings
Extension Water Quality Specialist
Publication Number: HE-419
Last Electronic Revision: March 1996 (JWM)
Drinking water supplies may be contaminated by many sources. Hazardous household wastes, septic systems, lawn and garden chemicals, leaking fuel storage tanks, animal waste, agricultural chemicals, landfills, and leaching of metals from plumbing systems may contaminate water.
Contaminated water may have off-tastes, odors, or visible particles. However, some dangerous contaminants in water are not easy to detect. Accurate water testing is needed to determine safety and quality. Water testing also identifies the need for water treatment equipment.
When water is contaminated, it is best to eliminate the source of the contamination, if at all possible. If this cannot be done, then water may need to be treated. Treatment can reduce common contaminates, such as sediment, calcium, iron, magnesium, sulfate, nitrates, arsenic, or lead. Water treatment can produce a clearer, safer, better tasting, and better smelling water, better suited for household use. Some typical water quality problems and recommended treatment systems are listed in Table 1. There are eight general types of treatment systems available for household use. These include carbon filters, fiber filters, reverse osmosis units, distillation, neutralizers, chemical-feed pumps, disinfection, and softeners. These systems range in cost from a few dollars to several thousand dollars, depending on the type of system and the type of contaminants.
Before buying, consider:
Some systems treat all the water in the house, while others primarily improve safety and quality of drinking water. Before buying water-treatment equipment, have your water supply tested by a recognized, certified water-testing lab. You need to identify the type and level of contaminants if you are to get the right system.
|Table 1. Typical Water Qually Problems and Recommended Treatment Systems|
|Problem||Recommended Treatment SystemsDisinfection|
|Bacteria and other microorganisms||Disinfection|
|Taste and odor||Carbon filter|
|Hydrogen sulfide gas (rotten egg odor)||Oxidizing filter followed by carbon filter; chlorination followed by sediment filter|
|Sediment (suspended particles)||Fiber filter|
|Hardness (calcium and magnesium)||Softener|
|Dissolved iron||Softener ffor up to 5 milligrams per liter); Iron filter; chlorination followed by sand filter and carbon filter|
|pH (acid or alkaline conditions)||Neutralizing filter or chemical-feed pump|
|Organic chemicals (pesticides, fuel products)||Carbon filter|
|Metals (lead, mercury, arsenic, cadmium), and other minerals (nitrate, sulfate, sodium)||Reverse osmosis unit; distillation|
Carbon filter cartridges must be replaced when taste or odor problems reappear. Carbon filters and replacement cartridges range in price from a few dollars to several hundred dollars. Some units may require professional installation. Four types of carbon filters, based on their location in the plumbing system, are shown in Figure 1. These are: (1) faucet mount; (2) in-line; (3) line bypass; and (4) point of entry (POE). Other types of carbon filters are pour through (portable) and specialty filters.
Faucet-mounted carbon filters attach to the faucet where drinking water comes out. These filters contain only a small amount of carbon and are not as effective as other types of carbon filters. One design includes a bypass option, which diverts non-drinking water around the filter to prolong the life of the carbon cartridge.
In-line carbon filters are installed beneath the kitchen sink in the cold water supply line. This does not allow for bypassing the unit for non-drinking water uses.
Only the cold water from the tap is treated. Warm or hot tap water will contain untreated water.
Line bypass carbon filters also are added to the cold water supply line, but a separate faucet is installed at the sink to provide treated drinking water. The regular tap delivers untreated water. The carbon filter lasts longer because only water used for drinking is treated.
Point of entry (POE) carbon filters treat all water entering the home. This type of filter is recommended for treating volatile organic compounds (VOCs) that easily evaporate into the air. These are the most expensive filters to purchase and maintain.
Pour through carbon filters are similar to drip coffee makers and are the simplest and least expensive type. They are portable, require no installation, and are convenient for camping or similar uses. They treat only a little water at a time and are not as good at removing impurities as other types of carbon filters.
Specialty carbon filters attach to the cold water supply line to appliances. Ice maker filters are placed on the supply line to refrigerators, and scale filters are placed on the supply line to water heaters or humidifiers.
An RO system usually includes:
Different sizes are available. They can be installed under the sink or in a remote location, depending on the size of the water-holding tank. Match its capacity to the number of gallons used per day. A household of four people normally finds 5 gallons per day enough.
A reverse osmosis unit is expensive (typically $600 to $900), and renting is an option. There are maintenance costs, because the RO membrane needs replacing according to the manufacturer's recommended schedule. Weigh the cost of a unit against the type and amount of contaminants and your concern for safety. Also compare the cost of an RO unit to other alternatives, like bottled water.
When the distiller is operating, tap water in a boiling tank (often made of stainless steel) is heated to boiling. Steam is produced, rises, and leaves most impurities behind. The steam enters condensing coils, where it is cooled and condensed back to water. The distilled water then goes into a storage container or is piped to a special faucet.
Storage containers can be glass, metal, or plastic. Each type is satisfactory when cared for as the manufacturer directs.
Large distillers can distill about one-half gallon of water per hour. Smaller units produce less than one quart of water per hour. The cost of producing distilled water depends on the appliance and the local electric rate. Although the distiller has no parts to replace, it is not maintenance-free. Scale must be removed from the boiling tank. Frequency of cleaning the distiller varies with the quantity of impurities in the water and the amount of water distilled. White vinegar or a manufacturer's cleaner is used for cleaning.
It may cost $250 for a small unit to over $1,450 for a large unit. Electricity makes operating costs higher than alternative treatment systems. Consider how much water you need, how contaminated your water supply is, costs, and alternatives like bottled water before buying a distiller.
Tank-type neutralizing filters or chemical-feed pumps that inject a neutralizing solution into the well neutralize acid water. If iron treatment is needed, the chemical-feed pump system is required. Tank-type neutralizing filters pass the water through granular calcite (marble, calcium carbonate, or lime) or magnesia (magnesium oxide). They treat water as low as pH 6. They must be installed after the pressure tank. These systems make the water harder.
For water less than pH 6, chemical-feed pumps inject a neutralizing solution of soda ash (sodium carbonate) or caustic soda (sodium hydroxide) into the well. This raises the sodium content of the water. Potassium can be substituted for sodium, but potassium is more expensive. Keep the solution tank full and adjust the feeder to provide the correct rate to result in a pH of near 7. For water between pH 4 and pH 6, use soda ash mixed at one pound of soda ash per gallon of water. Feed this solution into the well at a rate to raise the pH to near 7 at the faucet farthest from the well. For water less than pH 4, use caustic soda. This material is extremely dangerous. Wear gloves and goggles. Slowly feed a solution of one pound of caustic soda per gallon of water into the well at a rate sufficient to result in pH 7 at the faucet farthest from the well.
Neutralize alkaline water (greater than pH 7) by feeding diluted sulfuric acid in the same manner as soda ash. Use caution in making solutions from strong acids. Always add acid to water slowly. Never add water to acid: Use gloves and goggles when preparing solutions.
Continuous chlorination systems consist of a chemical metering device that feeds chlorine in sufficient amounts to kill bacteria. Chlorine must be in contact with water at least 1 minute to kill all bacteria. A chlorine residual of about 3 to 5 parts per million should remain to indicate that disinfection is complete. Typical chlorine feed rates are about 1 cup of 5 percent laundry bleach per 300 gallons of water. This rate depends on water temperature, pH, and pumping rate. Use an inexpensive chlorine residual kit to determine if the feed rate should be adjusted up or down to obtain the proper chlorine residual. If chlorine taste is a problem, use a carbon filter to remove excess chlorine from drinking water.
Before investing in a continuous chlorination system, it is wise to try repeated shock chlorinations. This simple process involves adding high concentrations of chlorine directly to the well to kill all existing microorganisms. Use this process to disinfect all new and repaired water systems. Shock chlorination can be done using ordinary laundry bleach (containing 5.25 percent sodium hypochlorite). The goal is to add enough chlorine to raise the concentration in the well to about 200 milligrams per liter to kill potentially harmful bacteria and viruses. If iron bacteria are a problem, concentrations of 800 milligrams per liter may be necessary.
Follow these safety precautions when using shock chlorination procedures:
Shock chlorination procedure:
Test the water for bacteria two weeks after shock chlorination to see if you have a recurring problem. Contact your local Health Department for information on water testing and well protection.
|Table 2. Recommended Amounts of Laundry Bleach for Well Disinfection Height of standing|
|Height of standing water (feet)||4-inch well||6-lnch well||8-inch well||12-inch well||24-inch well|
|50||1 quart||2quarts||1 gallon||2 gallons||8 gallons|
|100||2 quarts||1 gallon||2 gallons||4 gallons||16 gallons|
|200||1 gallon||2 galions||4 gallons||8 gallons||32 gallons|
The calcium and magnesium that cause hardness are reported as grains per gallon, milligrams per liter (mg/ L), or parts per million (ppm). Hard water, when used with soap, causes soap deposits that will not dissolve.
Water is softened by passing through a bed of ion-exchange resin. The softening process exchanges calcium and magnesium ions in the water for sodium ions in the resin. About 15 mg of sodium are added per gallon for each grain of hardness reduced.
When the sodium is used up, the softener needs to be regenerated. This is done by backwashing to clean the ion-exchange material, brining with salt (sodium chloride) to replace sodium ions, and rinsing to remove any excess salt.
A water softener removes small amounts of dissolved iron (5 to 10 ppm). However, if there is oxidized iron or iron bacteria in the water, the ion exchange resin becomes coated or clogged and loses its softening ability. In this case, use an iron filter or chlorination to remove iron.
The size water softener needed depends on the hardness of water, the quantity to be softened, and the length of time between recharging. There are three types of ion-exchange softeners for the home.
MANUAL. Each step for recharging the unit must be activated by hand. Salt is added directly to the single tank of this softener.
SEMI-AUTOMATIC. The homeowner sets the switches when the system needs recharging. The system completes the process by itself. A second tank is needed for the brine system.
AUTOMATIC. All steps of the recharging process are controlled by a timing mechanism that the homeowner sets, based on water usage. Some models can measure water usage or remaining softening capacity and recharge themselves only when needed. Most water softeners have a fully automatic recharging feature. These softeners also require a second tank for the brine solution.
Water softeners can be installed in various ways. Most people soften hot and cold water but bypass outside water lines.
The increased sodium in softened water is a concern to people on a sodium-restricted diet. Therefore, some water softener installations bypass the cold water line in the kitchen only.
Water softeners can be rented or purchased. Renting a softener or ion-exchange resin tank is convenient since the user does not worry about maintenance or regeneration. The dealer regularly replaces the ion-exchange resin tank, so a second tank for the brine solution for recharging is not needed.
A water softener can cost $500 to over 41,500, but owning the equipment could be more economical in the long run than renting it. The cost of the water softener is balanced against the savings of soft water. Using soft water reduces the quantity of cleaning products needed by as much as 500 percent. The home's plumbing system and water-using appliances will last longer. Other benefits include the time saved in cleaning and removing scale and better results in laundry, dish washing, and personal grooming.
For additional informatlon on water testing and treatment, contact your local North Carolina Cooperative Extension Service center. Some publications that may be useful are:Not shown: Figure 1.
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