Residential Drinking Water Treatment

An adsorptive filtration system is typically installed as a whole-house system (POET). In adsorptive filtration, the contaminant sticks to the surface of a specially designed filtration as the water flows through the filter.

Examples of adsorptive media are activated alumina and granular ferric (iron) hydroxides to lower arsenic levels.

If you are installing an adsorptive filtration system to reduce a contaminant with a health effect, make sure to install a system with an NSF/ANSI Standard 53 Certification. 

Aeration is typically installed as a whole house system (POET). It can release gases, such as radon or hydrogen sulfide, from water. It can also add oxygen to the water to convert a dissolved contaminant into its solid form so that it falls out of the water as particles.

This type of treatment is typically installed in combination with a filter that uses media to catch the particles that fall out. It can lower levels of iron, manganese, and sulfur.

Anion exchange is typically installed as a whole house system (POET). Anion exchange is a treatment like water softening but uses a different media that exchanges the contaminant for another anion (negatively charged ion), typically chloride.

Anion exchange units are typically used to lower levels of nitrate but can also lower levels of uranium, sulfate and fluoride. Anion exchange can be used to treat chloride, but this is typically not recommended.

Anion exchange units lower the pH, which can make the treated water more corrosive. This can cause issues with lead and copper plumbing and fixtures. If you have metal plumbing, it is necessary to follow the anion exchange unit with a neutralizing system.

Iron and turbidity may foul anion exchange units, so pretreatment to remove iron or turbidity may also be necessary.

Carbon filtration systems can be installed as a whole house system (POET), but are more frequently installed at or under the kitchen sink (POU). They use a filter with carbon in it. As the water moves through the filter, the contaminant is trapped by the carbon until the filter is saturated.

Carbon filters are often used to remove general taste and odor problems. Carbon filters are also effective at removing organic compounds and gases such as PFAS and radon.

Since the carbon filter can remove other minerals found in your water, it is difficult to know how long it will last. Some large carbon filters have been known to last for years, while some small filters may last for only weeks. Make sure to install a system with an NSF/ANSI Standard 42 or 53 Certification. 

Distillation units are typically installed at or under the kitchen sink (POU). They boil water and then condense the steam. The contaminant is left behind during this process, along with hardness and other minerals.

A pre-treatment system may be needed when using distillation to treat some contaminants. Make sure to install a distillation unit with an NSF/ANSI Standard 62 Certification. 

Flushing is a temporary solution to lower levels of lead and copper until a permanent solution has been chosen. Flushing out water that has been sitting in pipes can sometimes lower levels of lead and/or copper in your water below the health advisory level.

To flush, let the cold water run until it is as cold as it can get. This means the water is flowing directly from the well or the town water main. This flush should be done if the water has been sitting in the pipes for more than six hours, which is usually first thing in the morning or after the workday. Test the water after flushing using this method to show that flushing was successful in lowering the lead and/or copper levels.

Neutralizers are added to the water to make it less acidic by increasing alkalinity and pH. The most common neutralizing media are marble, calcium carbonate, soda ash or lime. This is typically installed as a whole house system (POET) and is often required following a POET reverse osmosis or anion exchange system.

The neutralized water will be less likely to dissolve lead and copper in a home’s plumbing.

An oxidizing chemical is added to the water to convert the dissolved contaminant (typically iron or manganese) in the water into a solid form so that it can be filtered out of the water.

For manganese, a strong oxidizing chemical such as chlorine or permanganate is required. Oxidizing chemicals require careful safety precautions, calibration, maintenance, and monitoring. Make sure to install a system with an NSF/ANSI Standard 42 or 53 Certification.

When an oxidizing catalyst filter media is used, the dissolved iron or manganese attaches to the coating on the filter. The iron or manganese is then converted to a solid form and filtered out. Make sure to install a system with an NSF/ANSI Standard 42 or 53 Certification.

Older plumbing and fixtures (for example, kitchen faucet) are more likely to contain higher concentrations of lead and copper than new materials. Replacing old plumbing with newer materials can lower concentrations of lead and copper in your water. Make sure to choose materials that meet lead-free certification standards.

It is important to clean aerators and flush new fixtures and plumbing after you have replaced any plumbing or fixtures. This helps to remove any lead particles that were dislodged during remediation.

A reverse osmosis (RO) system is typically installed as a separate tap by the kitchen sink (POU). It uses a synthetic membrane that allows water to pass through but leaves the contaminant behind. The membrane is continually rinsed.

RO systems are typically used to treat contaminants such as arsenic, copper, uranium, lead and nitrate.

RO treatment efficiency is only about 25%, which means that for every 1 gallon of treated water, there will be 3 to 4 gallons wasted. This is why it is best as a POU system and used only for drinking and cooking water. The filtered water is stored in a small pressure tank and dispensed through a dedicated tap and the wasted water is directed to the septic system or a drywell.

Hard water can cause scale on RO membranes and a pre-treatment system may be needed, such as a water softener. Be sure to read the manufacturer’s instructions for the maximum hardness concentration of your water before it goes through the RO membrane. In general, hardness concentrations should not be higher than 120 to 170 mg/L (milligrams per liter) or 7 to 10 grains per gallon. Make sure to install an RO system with an NSF/ANSI Standard 58 Certification.

This treatment option is for drinking water contaminated with bacteria after repairs have been made to the system. Shock chlorination is not intended as a solution for a bacteria problem that keeps occurring.

You can disinfect your own well and water system, or you can contact a licensed well driller for assistance. Find a guide to disinfecting your drinking water system.

Continuous chlorination is one of several permanent solutions to contamination from bacteria. It is typically installed as a whole house system (POET). It will disinfect water as it comes into your home by injecting exact amounts of chlorine into your plumbing system when the water is being pumped into the home.

Ultraviolet (UV) light treatment is typically installed as a whole house system (POET). UV light treatment is for bacteria will disinfect water without the use of chemicals. The effectiveness of UV light in killing microorganisms is directly related to the bulb’s intensity and exposure time.

Pretreatment is often necessary if there are water quality issues that may block the UV light, such as tannins, suspended sediment, scaling (due to hard water) and turbidity. Bulbs need to be replaced regularly. Make sure you install a UV light treatment system with an NSF/ANSI Standard 55 Certification.

A conventional water softener (also called a cation exchange system) is typically installed as a whole house system (POET). It exchanges the contaminant for sodium or potassium, which remains in the water. The contaminant is flushed away with the wastewater when the softener is cleaned.

Water softeners are typically used to remove hardness but can also remove contaminants such as radium, iron and manganese.

Make sure to install a water softener with an NSF/ANSI Standard 44 Certification. Consider choosing one with “on-demand” regeneration based on water consumption instead of timer-based.

The NSF/ANSI Standard 44 Certification assures that the product meets strict salt efficiency requirements. If you are dealing with iron or manganese, consider using non-salt treatment technologies such as an oxidation and filtration system.