Filtering or treating drinking water at home

Learn about drinking water filters, and, if you choose to use one, how to pick the right one for you.
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Water filtration basics

Do I need to filter my drinking water?

In most cases, no. We deliver high-quality water that meets or exceeds all state and federal drinking water standards. You don't need to filter the water unless you have a taste preference, health condition, or water quality issue specific to your home (such as lead leaching into the water from your home plumbing).

What issues can a home water filter address?

  • Lead leaching into water from household plumbing. While lead is rarely found in our source waters and there are no known lead service lines in Portland's distribution system, lead is in the plumbing of some homes and businesses. Lead in that plumbing can dissolve into drinking water when the water sits in the pipes for several hours. A lead-certified filter will remove lead.
  • Taste and odor preference. You might prefer the taste and smell of filtered water, or you may have old iron pipes in your home that affect the taste of your water, and you'd like to filter out that taste.
  • Chlorine sensitivity. If you have a chloramine (chlorine + ammonia) sensitivity, you might prefer to filter your drinking water or install a showerhead that removes chloramine.
  • Cryptosporidium in the water. We do not currently treat for the microorganism Cryptosporidium. If you have a compromised immune system, your health care provider might advise you to filter your water to remove Cryptosporidium cysts. Find more information below in the "I'm immunocompromised. What filter should I use to remove Cryptosporidium?" section.

How do water filters work?

Home filtration systems generally use carbon, charcoal, or a blend of filter media to remove contaminants as water flows through the filter. Depending on the type of filter, contaminants either get trapped in the pores of the filter or adhere/absorb to the surface of the filter media. In reverse osmosis (RO) systems, the water is usually treated with a pre-filter, a carbon filter, an RO membrane, and a post-filter.

Choosing a water filter

What should I know before buying a home water filter or treatment device?

The first step is to determine what you want the filter or treatment device to do. Do you want it mainly to remove tastes and odors? To remove contaminants, such as lead? Before you buy a filter, you may want to find out if the contaminant is a problem in your home. To determine if your home plumbing contains lead, request a free lead-in-water test kit online. To learn more about Portland's water quality, visit our drinking water test results page

Not all filters are the same. Read the packaging carefully and only purchase a filter certified by NSF/ANSI (National Science Foundation/American National Standards Institute). Here are some standards to look for:

  • NSF/ANSI Standard 42: Filters with this certification change the aesthetics of the water and reduce non-health-related contaminants. The contaminants reduced will vary by filter.
  • NSF/ANSI Standard 53: Filters with this certification reduce contaminants that are harmful to health. The contaminants reduced will vary by filter.
  • NSF/ANSI Standard 58: This certification applies to reverse osmosis treatment systems.
  • NSF/ANSI Standard 177: This certification applies to showerhead filtration systems, for the reduction of free chlorine.

Don't rely on the NSF/ANSI certification alone; make sure the packaging specifically lists the contaminant you wish to reduce. For example, you may find two filters that are both NSF/ANSI 53-certified, but only one of them may be certified for lead reduction.

I'm immunocompromised. What filter should I use to remove Cryptosporidium?

Choose one of the following types of filters to remove Cryptosporidium:

  • Reverse osmosis filters.
  • NSF/ANSI 53- or 58-certified filters that also include the language "cyst reduction" or "cyst removal."
  • Filters with an "absolute" pore size of 1 micron or smaller. If the package only states "nominal" pore size of 1 micron, then it may not remove all Cryptosporidium.

Follow the manufacturer's recommended filter cartridge replacement schedule. Because filter cartridges collect Cryptosporidium, it's a good idea to have someone who is not immunocompromised change them. It's also a good idea for that person to wear gloves while changing the cartridge. Learn more about Cryptosporidium and home water filtration at the CDC's Filtering Tap Water page.

What types of certified filters are on the market?

There's a variety of filters out there. They include pour-through pitchers and carafes, faucet-mounted filters, countertop and under-sink filters, showerhead filters, and refrigerator filters.

What is the difference between a point-of-use filter and a point-of-entry filter?

Point-of-use filters treat water only where and when you need filtration, such as at your kitchen sink or refrigerator. Point-of-use filters are often more economical, but if you wish to treat water at multiple locations in the home, you will need to buy a filter for each location. Point-of-use filters are a good choice when you want to remove contaminants that originate in your home plumbing (such as lead).

Point-of-entry filters treat all water that enters your home. This will include your kitchen sink and refrigerator, of course, but also your toilet water, bath water, laundry water, and in some cases water at your outside spigots. Point-of-entry filters may be more expensive, and will not address issues in the plumbing that cause problems after the filter (such as lead solder in your household pipes). If you use a point-of-entry filter that removes chlorine and sodium hydroxide, it's important to keep in mind that you are removing the disinfectant and pH adjustment in your tap water. This could lead to bacterial growth and corrosion of home plumbing.

Where can I buy a filter?

You can buy filters online and at hardware stores, grocery stores, and other retailers.

Do showerhead filters remove chloramine?

The NSF/ANSI Standard 177 is for showerheads that reduce free chlorine. Since Portland uses chloramine (chlorine + ammonia) and not free chlorine, filters with the NSF/ANSI standard may not work effectively. Some certified showerheads on the market with granular activated carbon claim to also reduce chloramine. You may have success with vitamin C showerhead filters, but these are not certified. 

Maintenance and cost

Do filters require maintenance?

Yes. If your filter cartridge is not replaced according to the manufacturer's guidelines, you run the risk of it no longer performing as designed.  For example, a filter designed to remove 99 percent of lead can only do so for a specific volume of water. Filters that are not maintained or replaced according to the manufacturer's schedule can also harbor bacteria. Many filters have a device that indicates when to change the filter.

How much do filters generally cost?

Certified water filters start around $20, with replacement filters being less expensive than the initial device. Filtration pitchers and faucet-mounted filters generally cost less than filters that are plumbed in below a sink. Reverse osmosis systems are more expensive than carbon filtration systems. When choosing a filter, consider filter replacement costs and only purchase a system that you are willing to maintain.

What should I do if my filter keeps clogging?

Many filters will have lower flow as they near the end of their lifespan, indicating that they need to be replaced. Portland's drinking water is unfiltered, so filters may not last as long as they would in a filtered water system. Also, if you have older iron pipes, corrosion particulates may cause your filter to clog prematurely. If clogging is frequent, contact the Water Quality Line.

Filtration alternatives

Are there alternatives to filtration?

The most straightforward alternative is to not filter or treat the water at home, since Portland's water meets or exceeds state and federal standards. If you have lead in your plumbing and haven't used the water for several hours, running your water for 30 seconds to 2 minutes will flush the lead out. Flushing your faucet will also address taste and odor issues if you have older iron pipes. 

To remove chlorine taste and odor, try adding lemon slices to a pitcher of water, as the ascorbic acid (vitamin C) will help dechlorinate the water. Boiling water can also reduce chlorine levels; however, you should not boil water to remove lead. Bringing water to a rolling boil for one minute will also disable Cryptosporidium cysts.


NSF Certified Product Listings for Lead Reduction

NSF Guide to Selecting a Home Water Filter