Household Water Systems

Household Water System ComponentsWater Source (well, spring, pond, or cistern)PumpPressure TankPressure SwitchCheck ValvePiping Optional Treatment Equipment(Softener, Filter, Disinfection Unit, etc)

Typical Shallow-Well Water System

PUMP POWER CONTROL BOX

SHALLOW-WELL JET PUMPCHECK VALVEWELL CASINGSUCTION PIPE

SUPPLY PIPE TO HOUSEPRESSURE TANKPRESSURE SWITCH

Water Pump Options

Pump House with Shallow Well PumpPRESSURE SWITCH

Jet Pump InstallationsShallow-Well Jet PumpDeep-Well Jet Pump (Two-Pipe System)

Intake PipeTo Pressure TankPressure Pipe (Return Flow)Lift Pipe (Upward Flow)

Jet Ejector (Venturi)NozzleWaterJet Pump Schematic DiagramIncreases practical suction lift by diverting part of the pump discharge to the ejector on the lift pipe The greater the suction lift, the greater the percentage of discharge water must be divertedMaximum practical lift is limited to approximately 200 feet by economics

Deep-Well Jet Pump Ejector UnitsTwo-Pipe System

Well CapReturn PipeLift Pipe(w/ Venturi)Nozzle

Foot Valve Intake StrainerPacker System

Return FlowLift Pipe(w/ Venturi)NozzleFoot ValvePackerSuction Pipe

Submersible Water Pumps- Good for deep wells High efficiency Wells as small as 4 diameter

Submersible Pump with Pitless AdapterFROST LINE

Pressure Switch Controls water pump Turns on when system pressure drops to 20 (30) psiTurns off when system pressure rises to 40 (50) psiLow pressure shut-down in case well water level drops

Pressure TankIs not meant to provide household water storageDelays pump turn-on and extends pump run timeEliminates frequent, short On/Off cycles which can burn up the pump motorVolume of pre-charged tank should be at least 6 times the delivery of the pump in 1 minuteVolume of uncharged tank should be at least 10 times the delivery of the pump in 1 minute

Pressure TankTypical uncharged pressure tank (no air bladder/diaphragm) installationPipe Plug(to be removed when system is drained to correct waterlogging)Pressure SwitchDelivery Pipe from PumpMain Power Cutoff Switch

Useable Storage Capacity of Pressure Tanks Over Normal Operating Range(Not Pre-charged)42 gallons40 lbs20 lbsWater Level at 12 gallons 82 gallons

Examples of Pre-charged Pressure Tanks

Effect of Waterlogging on Useable Pressure Tank Capacity

WaterloggingTo correct waterlogged pressure tanks:-Turn off power to pumpOpen a faucet to drain systemRemove pipe plug at top of tank to let air into tank and finish draining systemReplace pipe plug (use teflon tape or pipe compound to seal properly)Close faucetTurn on powerRepeat this process whenever the pump begins starting immediately every time a faucet is openedPipe Plug(to be removed when system is drained to correct waterlogging)Power Switch

Controlling Waterlogging in Pressure Tanks

Submersible Pump Check Valve CutawayWater Flow

Household Water RequirementTypical Usage: 50-100 gallons/person-day (drinking, bathing, laundry, toilet flushing, dishwashing, cooking, etc.)Well Flow Rate Requirement:Minimum Acceptable Rate: 5 gpmPreferred Rate:10 gpmMinimum Fire Protection Rate:20 gpm

Household Water Requirements

Farmstead Water Requirement(Flow Rate)

Intermediate Water StorageImproves usability of low-yield wellsWell pump operates at low flow for extended periods (overnight) to fill storage tankPressure pump uses water from storage to supply immediate household demandMinimum intermediate storage capacity should be at least equal to daily household water use(2-3 days storage capacity preferred)

Intermediate Storage for Low-Yield Wells

Intermediate Storage Tank(filled by submersible well pump)Pressure TankPressure PumpLow Yield Well Water SystemInlet from Well PumpPressure Pump Suction LineSupply Line to HouseCheck Valve

Water Treatment EquipmentDisinfection EquipmentFiltersWater Softeners

Water Disinfection Options-Bacteria & Viruses-ChlorinationShock chlorinationContinuous chlorinationDry pellet chlorinatorChlorine solution feed pumpChlorine solution venturi injectorOzonationUltraviolet Irradiation

Shock ChlorinationUse laundry bleach (5.25%) w/ no additivesPour 4 pints of bleach into well vent for each 100 gallons of water in systemRecirculate water into well for 20 minutesOpen all outlets until bleach is smelledLet system stand idle overnight (4 hrs minimum)Flush systemRe-test for bacteria after 10-14 days of use

Dry Pellet Chlorinators-Electric powered (110 or 220 volt) -Controlled by pump controllerFew moving partsUses calcium hypochlorite tabletsTreats water in the wellLonger Cl contact timeNo solutions to mixTreats up to 20 gpm

Venturi Solution InjectorInjects any liquid solutionInjection rate proportional to water flow rateAdjustable over wide range of flow and injection rates

Metering PumpInjects any type of solutionControlled by water pump controllerConstant injection rateAdjusts to wide range of flow and injection rates

SIGHT PORTUltraviolet Disinfection Unit

Water Treatment Options- Iron or Manganese -Shock ChlorinationContinuous ChlorinationDry pellet chlorinatorChlorine solution feed pumpChlorine solution venturi injectorOzonationOxidizing (Greensand) FilterIon Exchange Water Softener

Iron Treatment Options

Water Treatment Options-Corrosion-Neutralizing FilterLimestone chipsMarble chipsCaustic Soda (NaOH) Feedermetering pump or venturi injectorSoda Ash (Na2CO3) FeederMetering pump or venturi injector

Water Treatment Options-Hydrogen Sulfide (H2S) Rotten Egg Odor-Activated Carbon FilterOxidizing FilterShock ChlorinationContinuous ChlorinationDry pellet chlorinatorChlorine solution metering pump Chlorine solution venturi injectorOzonation

TDS/Mineral TreatmentReverse OsmosisDistillation

4-stage Reverse Osmosis Unit with Tank and Faucet

Reverse Osmosis SystemsReduce mineral concentrations by 90%15 gallon/day under-sink units: $150-$300Require pre-softening with hard waterOperate on water system pressure (40 psi)Wastewater:Treated water ratio 4 or 5:1Membranes: $70-100 each; 5 year life

Distillation UnitHeating ElementVaporization ChamberCondensing CoilGas VentRaw Water InletDistilled WaterRising SteamDrain

Countertop Distillers initial cost $150-$1000 4-8 hours/gallon treatment rate 2.75-3.0 kWh/gallon energy consumption removes 99.9% of all contaminants electric co-ops often subsidize purchase

Carbon FiltersRemove contaminants by adsorption on carbon particle surfaceHierarchy of contaminant adsorptionSaturated filters can actually increase concentration of some contaminantsNot effective on nitrate, hardness or bacteriaFilter cold water onlyBigger is better - more surface area

Cartridge FiltersFilter WrenchFilter HousingCarbon Cartridge (taste, odor, chlorine, organics)Particle Cartridge (sand, sediment)

Ion Exchange Water SoftenersExchange sodium ions for calcium and magnesium ions in waterIncrease EC somewhatMay be dietary hazard - hypertension (adds 140 mg/l of sodium in Hard water)Use potassium salt (KCl) for health reasons

Ion exchange softeners replace Ca++ and Mg++ with Na+ ions.Zeolite medium is recharged with Na+ by NaCl brine when depleted.

Ion Exchange Water Softener with Sensor- Controlled Recharge

Softener Selection ConsiderationsRequired grain capacityDaily water use (household population)Water hardnessDesired regeneration scheduleInitial costWater conservationOther (Iron removal, etc.)

Ion Exchange Water Softener CapacityRated by grains of hardness treated between regenerations1 grain/gallon (gpg) = 17.1 mg/lExample:Water hardness = 200 mg/l = 200/17.1 = 11.7 gpgSoftener Capacity = 30,000 grainsHousehold Population = 4 personsCalculate:Water Use = 4 persons x 50gal./person-day = 200 gal./dayDaily Hardness Treated = 200 gpd x 11.7 gpg = 2339 grains/dayRegeneration Interval = 30,000 grains/ 2339 grains/day = 12.8 days

Recommended Softener Sizes

Ion Exchange Water Softener Recharge Control Method

-Time Clock-Flow Meter-Hardness SensorWater Use+-

Initial Cost-+

Typical Programmable Water Softener Controller

Water SofteningPermanent magnet water softeners dont workElectrostatic and catalytic descalers may descale water, but dont soften itScale will not buildup on pipes, water heater elements, bathtubs etc.Sudsing action of soaps is not improved

Private Water System Resources

Private water systems provide household water to the majority of rural residences in the state.The components of a typical water system are the water source, normally a well, a pump to pressurize the water, a pressure tank, pressure switch and check valve to maintain the system pressure between pump cycles, and the piping to convey the water to points of use. Systems may contain point-of-use or point-of-entry treatment equipment to improve water quality before use. Point-of-entry treatment is sometimes called whole-house treatment equipmentHere is the arrangement of components in a typical shallow-well water system with a jet pump.Wells are the most common source of household water. Depending on the depth to water in the well, different pumps may be necessary to lift and pressurize the water. For very shallow wells with a pumped water level less than about 18 feet an ordinary centrifugal pump will work. Remember that the water level in a well falls as water is pumped, maybe as much as 20 feet for every 1 gpm of pumping rate. For depths up to about 28 feet a shallow-well centrifugal jet pump will work. Deep well jet pumps will function satisfactorily up to depth of 200-250 feet. Multi-stage submersible pumps can lift water from depths of over 500 feet. Regular horizontal centrifugal pumps tend to be the least expensive per unit capacity, while submersible pumps tend to be the most expensive.The components are normally in a pump house designed to house and protect water system equipment.Jet pumps are used to increase the suction lift of ordinary centrifugal pumps beyond their usual maximum of 15-20 feet. A shallow-well jet pump can lift water by suction up to about 25-30 feet. By moving the jet ejector to the bottom of the well, a deep-well jet pump can lift water by suction 200 feet or more. The greater the suction lift the less efficiently the pump operates.Jet pumps recirculate part of the water delivery back to the suction line to raise the pressure in the suction line sufficiently to prevent pump damage by cavitation (low-pressure boiling) in the pump impeller. The deeper the well, the greater the fraction of delivered water must be recirculated. Eventually, the water depth gets so great that other pump options become more economical.Here are the components of a deep-well jet pump.For deep household water wells, the submersible electric pump is the most common choice. The pump has several stages to generate enough pressure to lift the water out of the well and to pressurize is sufficiently for household use. The electric motor is long and narrow so it can fit down small household wells as small as 4 inches in diameter.Submersible pumps are often used with a pitless adaptor which allows the well to be situated in the open, without a pump house. All hydraulic connections are below ground where they will not freeze in cold weather. The pressure tank and related components can then be located in the house garage or basement or other convenient location.The pump operation is automatically controlled by the pressure switch. The switch is mounted on a small pipe fitting on the pressure tank or water line. When a faucet on the water system is opened and water begins to drain, the pressure will begin to drop. Once the pressure drops below the turn-on point, the switch closes and the pump will begin running, building the pressure up again. Once the pump has operated long enough to build up the pressure to the turn-off point, the switch opens and cuts off the pump operation.Without a pressure tank, the storage volume of the plumbing system would be so small that the pump would state immediately every time a faucet was opened and would shut off every time the faucet was shut. Frequent start/stop cycles can overheat a pump motor (starting current for electric motors is about 4 times normal running current) and burn it up. Adding the pressure tank with a large air volume allows the filling water to compress a spring in the system. This lets the system drain a few gallons of water before the pump turns on. Several short usages of water will not start the pump until enough pressure is bled from the system to reach the turn-on pressure. Once the pump starts it will operate for a minute or more until the air in the tank is compressed to the turn-off pressure.Here is a typical pressure tank installation with pressure switch in a pump house or basement.The amount of water that is drained from a pressure tank between the turn-on and turn-off points of the pump is called useable storage capacity and depends on the tank volume and the set points. Normally the turn on point is at 20 psi, but may be as high as 30 psi. Turn off usually occurs at 40-psi but may be 50 psi. The spread between the on and off points is normally 20 psi. Only a small fraction of the tanks volume is useable storage, 6.5 gallons for a 42 gallon tank between 20 and 40 psi. The recommended size of pressure tank is 10 times the pump flow rate for 1 minute for non-charged tanks, and 6 times the flow for pre-charged tanks. So a 10 gpm pump should have a 100 gallon non-charged tank or a 60 gallon pre-charged tank. This insures the pump will operate for nearly 2 minutes before shut-off every time it starts. The aim is to avoid frequent starting and stopping.Pre-charged tanks normally come with a bladder or diaphragm that is charged by an air compressor to about of the the turn-on pressure of the pump. This allows a smaller tank volume to produce a larger useable storage volume. Some tanks have a Schraeder valve (tire stem valve) that allows you to adjust the amount of pre-charge)Waterlogging occurs when prolonged usage allows the water to absorb the air volume in the top of the tank. The shrinkage of the trapped air volume effectively weakens the spring storing the built up pressure of the pump. Soon the volume is so small it is as though there is no pressure tank in the system, and the pump cycles on and off immediately whenever a faucet is opened or shut.To correct a water logged system, you must shut of the pump power supply, open a faucet to drain the system, remove a pipe plug in the top of the pressure tank to allow air back into the tank, put sealant on the plug threads and replace it, close the faucet and restore power to the pump. The system will function normally, but will immediately begin reabsorbing the air pocket in the tank. Tanks with diaphragms, wafers or air bladders, or systems with air entrainment valves will not become water logged.Some methods of controlling waterlogging in pressure tanks. The diaphragm, bladder and wafer systems create an impermeable barrier between the water and air pocket to prevent absorption of the air. The air entrainment system uses a venturi air injection system to bleed small quantities of air into the water as it is pumped and then uses a control valve on the pressure tank to vent excess air from the system. Normally, no maintenance on these types of systems. Some very old bladder and diaphragm systems used natural rubber, which is susceptible to decomposition by strong chlorine solutions. Treating a bacterial contamination in your water system with one of these old tanks can result in failure of the bladder/diaphragm and small chunks of black rubber in your water system. Modern tanks use neoprene, which is impervious to chlorine.The check valve prevents backflow into the well and traps the built up pressure in the water system. Submersible pumps have the check valve at the pump discharge port. Deep-well jet pumps normally have the check valve at the lower end of the suction line to the ejector unit (foot valve). Shallow well jet pumps have the check valve on either the suction port or on the end of the suction pipe. Failure of the check valve will cause the pump to cycle on and off continuously.Household water requirements typically range from 50 to 100 gallons per person per day. The rate at which water is delivered is just as important as the daily use. Too small a supply can lead to low system pressure and long fill times for washers and bathtubs. Insufficient flow prevents the proper operation of some appliances, such as water softeners, etc. The absolute minimum flow needed (often required by mortgage lenders before financing house construction) is 5 gpm, with 10 gpm being preferred. If 20 gpm can be maintained at a minimum pressure of 30 psi for 2 hours or more, insurance companies will often give reduced fire insurance rates for rural houses.These are typical water use requirements for various household appliances and fixtures. Normally all of these will not operate simultaneously, but this can give guidance for water system sizing. Water softener recharge is usually timed to occur between midnight and 5 AM to prevent interference with other household activities.If the household water supply will also be used for other purposes on the home site, those needs should be taken into account to prevent low system pressure or water shortages at critical periods.If the only water source available is a low-yield well (less than 5 gpm) it may be used if intermediate storage is provided. Since pressure tanks normally have only a small useable volume (15 gallons for a 100-gallon uncharged tank and 24 gallons for a 45-gallon pre-charged tank between 20 and 40 psi) another storage tank must be placed in the system. This tank is supplied by the well pump, controlled by a level control in the intermediate storage tank. The tank should have capacity sufficient to meet 2-3 days normal water use by the household. Once the volume is depleted by 5%, the well pump turns on and runs until the tank is refilled. The house plumbing system is charged by a pressure pump which draws water from the intermediate storage tank to supply the water system and pressure tank. As immediate demands deplete the intermediate storage tank, the peak water use periods are satisfied. When the use rate subsides and during non-use periods the water well pump continues to supply the storage tank. In this way, the household can begin each day with a full storage tank to meet immediate needs.Here is a schematic of a typical low-yield well water system with an intermediate storage tank. It is just like any other household water system, except for the large storage tank with well pump controls triggered by water level sensors in the tank. The intermediate storage tank is covered for sanitation reasons, but is not pressurized. The pressure pump is an ordinary centrifugal pump which takes water from the intermediate storage tank and pressurizes the household plumbing and pressure tank at normal operating pressures. A pressure switch controls the operation of the pressure pump, turning it on when pressure in the system drops to low and turning it off when the pressure reaches the maximum set point (usually 20 to 40 psi).Here is a photograph of an actual low-yield well water system with an intermediate storage tank. Many water systems in Oklahoma use water that is less than ideal for household use. Certain kinds of treatment equipment can be added to household water systems to improve the quality of the water for drinking and other uses. Disinfection equipment provides water that is biologically free of disease causing organisms. Filters can remove sediment and other contaminants. Water softeners remove calcium and magnesium ions which make the water hard and cause build up of scale in the water system.Chlorination is the most common disinfection method. If the well has been contaminated by a one-time occurrence (such as flooding, well or pump repair, water line break, etc.) shock chlorination will correct the problem. If the problem is an on-going source of biological contamination, a continuous chlorination system must be used: either a pellet chlorinator, a metering pump or a venturi injector. Treatment with ozone is possible for household water systems, but is expensive. Ultraviolet radiation can be used to kill viruses and bacteria in clear water.Shock chlorination is used to correct contamination from one-time events, such as flood waters entering the well, pump repairs or pipe breaks. Use ordinary household bleach with 5.25% sodium hypochlorite as the active ingredient. No scents or other additives, please. Remove the vent pipe in the well cap (remove well cap in case of pitless adapter) and pour 4 pints of bleach into the well for every 100 gallons of water in the well casing, the pipes, pressure tank, water heater, etc. Connect a hose to an outside hydrant and recirculate water into the well casing to stir the mix and to wash down the well casing, riser pipe, etc. About 20 minutes of contact time is needed to allow the chlorine to kill organisms on these surfaces. Turn off the power to the pump and drain the pressure from the system by opening a faucet in the house. This will ensure that chlorinated water enters the pressure tank in sufficient quantity. Restore power to the pump and open faucets one-by-one, starting with those nearest the well and moving to the far end of the system. Open both hot and cold taps at sinks, tubs and showers, flush toilets, operate chilled water dispensers and icemakers on the refrigerator, fill the washer and dishwasher, and open all outside hydrants. Once bleach is detected (ask assistance from someone who has not been handling concentrated bleach it may be hard for you to smell), let the system stand idle for at least 4 hours, and preferably overnight. Then flush bleach from the system. Use as normal, except for drinking if you have health concerns, for 10 days to 2 weeks. Take another bacteria test to confirm the system is now safe. Repeat the process if the second test is positive for bacteria. If a third test is positive, consider whether you have an ongoing source of contamination.Dry pellet chlorinators are simple and relatively inexpensive. An electric motor connected to the pump power cable operates whenever the pump is running. The motor turns a feed wheel that drops chlorine tablets into the well from a reservoir. The feed wheel speed can be adjusted to meet the chlorination needs for water flow rates up to 20 gpm. This unit treats the contamination problem right in the well. With this, or any other chlorination system, a residual chlorine testing kit should be used to check for residual (unconsumed chlorine) at the water tap. It advisable to have at least 1 ppm residual chlorine to ensure safety. More than 5 ppm is usually objectionable to most consumers.A venturi injector uses water pressure to draw a liquid chlorine solution into the water stream. Since treatment is done after the water exits the well, it is important to have sufficient contact time for the chlorine to work before the water is consumed. Depending on the water temperature and pH 15-20 minutes is normally needed before chlorine will complete its oxidization of contaminants. If not enough contact time exists it may be necessary to add a length of coiled polyethylene tubing to increase the travel time from the point of injection to the first point of water consumption.A solution metering pump uses a small piston pump or diaphragm pump to inject a liquid solution into the water system. The pump operates off of the same power cable as the water pump so it will operate whenever the water pump is running. The solution can be metered into the well, or injected into the water line. The chlorine solution is made up of liquid bleach (household bleach with 5.25% sodium hypochlorite without any scents or other additives). The solution may be diluted with water to achieve the desired concentration. Liquid chlorine solutions are volatile and large quantities should not be made up as they will lose potency due to vaporization.Ultraviolet disinfection units use the radiation from a special lamp to kill microscopic organisms in water. The water must be perfectly clear for this unit to function. The radiation will penetrate only a short distance into the water, so the flow is spread in a thin layer around the lamp. The flow rate of these system is very low to ensure enough contact time to kill all organisms. The strength of the lamp erodes over time, so the bulb must be changed as specified by the manufacturer even if it still appears to be functioning. Unlike chlorination and ozonation systems, UV treatment units work only on biological organisms. Hydrogen sulfide, iron and manganese are not affected by this treatment unit.Iron (red water) and manganese (black water) are common mineral contaminents in well water. Oxidation treatments such as chlorination and ozonation together with particle filtration will remove these nuisance contaminants. An oxidizing (greensand) filter will also treat these contaminants. An oxidizing filter works much like a water softener with a filter tank filled with a granular medium. The medium is charged with potassium permanganate to provide the oxygen to oxidize the contaminants. The medium must be recharged with a permanganate solution when it is spent. Ion exchange water softeners are rated by their manufacturers to remove small quantities of iron and manganese.Here are guidelines for treatment options for iron treatment based on the iron concentration in the water.If water is corrosive (low pH and low alkalinity) it will consume metal components in the plumbing system. This is usually noted by green stains under any faucets that may have slow leaks. The stain is a result o copper leaching from copper pipes and from bronze and brass components in the water system. Metal leaching can be serious if you have an old house with copper pipes soldered with regular (high-lead) solder). A neutralizing filter can raise the pH of water. It is a tank filled with limestone or marble chips that the water flows through. These filters increase the hardness of water. Caustic soda (lye) can also be injected into the water to raise the pH, but handling the solution can be dangerous. Soda ash can be injected as a safer alternative, but soda ash increases the hardness of treated water.Hydrogen sulfide gives water a rotten egg smell. It comes from sulfate reducing bacteria (non-pathogenic) that live in the well and convert sulfate to hydrogen sulfide. Small amounts may be removed by activated carbon filters. Oxidizing filters will remove larger amounts of H2S. Shock chlorination will reduce the problem for some period of time, but since it is usually impossible to kill all of the sulfate reducing bacteria, the problem returns. If treatment provides relief for 3-4 months or more, this treatment may be adequate. If the problem returns in a matter of days or weeks, continuous chlorination or ozonation will be needed.High salt content (total dissolved solids-TDS) and individual mineral concentrations can only be treated by reverse osmosis filtration or distillation. There are no economical treatment systems for high mineral content that treat the whole house water supply. These units are normally point-of-use systems. A whole house distiller is impractical, and whole-house RO systems that can treat 10 gpm will cost about $5000 initially.Reverse osmosis uses household water system pressure to reverse the tendency of water to flow through a semi-permeable membrane to try to dilute salty water.Here is a typical under-sink, point-of-use RO system with a third faucet. These units will reduce inorganic mineral content of water (including TDS, nitrate, sulfate, etc) by about 90%.Small point-of-use reverse osmosis (RO) systems can be purchased at home centers for about $200 for a 15 gallon per day unit. This is large enough to treat the drinking and cooking water for a family of 4. The unit consists of a sediment filter, 2 carbon pre-filters, a thin film composite (TFC) reverse osmosis membrane, and a final carbon/sediment polishing filter. The unit has a 3 gallon tank to provide some storage, and a 3rd faucet to be installed at the kitchen sink. The unit is meant for installation under the kitchen sink and can also supply water to the refrigerator chilled water dispenser and icemaker. It is plumbed into the cold water supply line, and the sink drain for wastewater disposal. At a 40 psi operating pressure it will produce about 4-5 gallons of waste water for every gallon of treated water. The TFC membrane costs about $70-$100 and should last for 5 years. Hard water will shorten its life, so if your water is hard, a whole house water softener should be installed first. The carbon filters are to remove residual chlorine which can destroy the membrane.

Distillers use vaporization and condensation to produce the purest water of any treatment unit. All inorganic minerals are left behind by the evaporating water, and volatile organic contaminants are vented from the top of the unit. The flow of incoming water cools and condenses the vapor back to liquid.Distillers are relatively inexpensive, but produce small quantities of water. They require electric energy to operate. Electric co-ops subsidize their purchase by rate payers because the provide a good year-round power consumption. They are practical only for drinking and cooking water.Activated carbon filters remove organic contaminants, tastes and odors from water by adsorption (attachment of contaminants to the surface of the filter particles by electro-chemical interaction). Carbon filters come in several forms from counter top, point-of-use units to whole-house filters. The filter may be in granular or block form. Their efficiency is based on the surface area of the filter element, so bigger is better. The filter should be used on cold water only. Running hot water through a filter breaks the adsorption bonds between contaminant and carbon. Once the filter is saturated with contaminants, the adsorbed contaminant with the lowest affinity will be dislodged by any incoming contaminants with a higher affinity for the carbon. For this reason a poorly maintained filter can reduce water quality. These units are often sold by disreputable salesmen as panaceas for every type of water problem, but they do not work for everything. They will not remove bacteria, nitrate, or most other inorganic contaminants. Because they remain full of water and are normally indoors in a warm environment, they can harbor bacteria. They are recommended for use only on biologically sound water (treated with chlorine, ozone or UV, or water that is tested and found to be negative for bacteria). They should be flushed for a few minutes before using water if they have been standing idle for a day or more.Under-sink cartridge filters can use several different types of filter elements. Here is a unit with a granular activated carbon cartridge on the left and a sediment filter cartridge in the center. Using the filter wrench the housing can be opened and either cartridge (or several others available) may be inserted to meet specific treatment needs.Ion exchange water softeners remove calcium and magnesium ions from water by replacing them with sodium ions. Calcium and magnesium (and iron to a lesser extent) make water hard, causing scale build up in pipes, on heating elements of water heaters and kettles, create bathtub rings, spots on air-dried dishes, reduced soap effectiveness and dingy laundry. Hardness is not a health hazard but a nuisance contaminant (it can be costly in terms of shortened life of system components and increased soap usage). Softeners will increase the TDS of softened water slightly (15% for calcium caused hardness and 92% for the less common magnesium). The addition of sodium to drinking water is a concern for some people with hypertension. For water that is rated as Hard (120 mg/l) softening the water will add 138 mg of sodium- about as much sodium as 1 slice of white bread. If that level of sodium is a concern, it is possible to use potassium chloride salt in water softeners. Potassium salt is more expensive than sodium salt, however.Here is a simplified illustration of the exchange process that occurs in a functioning water softener. When the salt is depleted, the softener is regenerated by backwashing it with a salt water brine solution to flush out the calcium and magnesium and recharge the medium with sodium.A two-tank water softener (one for the softening medium and one for the brine solution to recharge the medium when it is depleted). Recharge is controlled by a control valve. The valve can be activated manually, by a time clock, by a water meter, or in the case shown here by a hardness sensor. When the sensor detects hard water leaving the tank, it triggers a regeneration cycle. A time clock will not allow regeneration until a specified time of day (usually after midnight) so regeneration will not interfere with other household activities that require water.Softeners come in various sizes. The bigger the softener, the harder the water can be treated, the more water can be used between regenerations, and the more time can elapse between regeneration cycles. Bigger units are more expensive. But since each regeneration wastes some salt and water, fewer and larger generation cycles will be more economical than many small cycles. Other factors, such as iron removal capability, convenience, dealer reputation, etc. will influence softener selection.An estimate of the size of softener required can be made from the size of the household served and by testing water hardness. Here is an example calculation. This softener can operate nearly 13 days between regenerations at normal use rates.Here is a guide for sizing water softeners based on the size of the water supply and the hardness of the water. In each case the maximum water hardness is based on a 500 gallon usage between regenerations- the water use of a family of 4 in a 1-2 day period.The method of softener regeneration control affects the cost of the softener and the water use efficiency. They are inversely related. The more expensive the control unit, the more economical it is in terms of water use. All control systems will allow manual over-ride if you want to trigger regeneration at any time.Here is an illustration of a typical programmable, sensor controlled softener control unit. You can set the time of regeneration, the hardness level at which regenerating occurs, adjust the unit for use of potassium salt, and manually trigger regeneration, among other things.There are many salt-free water softening systems being sold. Most of them are snake oil. Tests by the Water Quality Institute of permanent magnet water softeners found them to be completely ineffective at changine the hardness of water of altering the build up of scale in water heaters. There are various electrostatic and catalytic descalers on the market. Some have testimonials by industrial users saying that they dramatically improve the quality of boiler feed water and prolong the life of industrial heat exchangers and boilers. Small, homeowner-sized units are on the market today. Most do not claim to be water softeners, but do claim to prevent the build up of scale in water systems.There are a number of print resources available to help answer water system questions. Home water Treatment by the Northeastern Regional Agricultural Extension Service (NRAES-45) contains information about several home water treatment devices. The Midwest Plan Service Private Water Systems Handbook (MWPS-14) contains information about all facets of home water systems from wells to treatment units. MWPS-14 is available through the OSU Plan Service (405-744-5425) for $7.00. A copy of MWPS_14 was included in the Water Quality Handbook your county received from the DASNR Water Quality Coordinator in 1992. The Oklahom*A*Syst program has a module on Drinking Water Well Management that provides much useful information of protecting your water well. It also contains a self-assessment worksheet to help homeowners evaluate the condition of their water well.