Water Filtration Basics
- Do I need to filter my drinking water?
- What issues can a home water filter address?
- How do filters work?
Choosing a Water Filter
- What should I know before purchasing a home water filter or treatment device?
- What types of certified filters are on the market?
- What is the difference between a point-of-use filter and a point-of-entry filter?
- Where can I buy a filter?
- Do showerhead filters remove chloramine?
- I'm immuno-compromised. What filter should I use to remove Cryptosporidium?
Maintenance and Cost
- Do filters require maintenance?
- How much do filters generally cost?
- What should I do if my filter keeps clogging?
Water Filtration Basics
The Portland Water Bureau delivers high quality water that meets or exceeds all state and federal drinking water regulations. Filtration is typically not required, however, you may have a taste preference, health condition, or a water quality issue caused by your home plumbing that filtration can address.
- Lead removal. While lead is rarely found in our source waters and there are no known lead service lines in Portland’s distribution system, lead can be found in the plumbing inside some homes and businesses. Lead in household plumbing can dissolve into drinking water when it sits in the pipes for several hours. A lead-certified filter will remove lead.
- Taste and odor preference. Some customers prefer the taste and smell of filtered water, or they may have old iron pipes in their home that impact the taste of their water.
- Chlorine sensitivity. Customers with a chloramine (chlorine + ammonia) sensitivity may prefer to filter their drinking water or install a showerhead that removes chloramine.
- Cryptosporidium cyst removal. Customers who are immune compromised may be advised by their health care provider to filter their water to remove Cryptosporidium cysts. More information in the Cryptosporidium filters section below.
Many filtration systems use carbon, charcoal, or a blend of filter media to remove contaminants when water flows through the filter media. Depending on the type of filter, contaminants either get trapped in the pores of the filter or they adhere/absorb to the surface of the filter media. For 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
Determine what you want a treatment device to do, such as remove tastes and odors, or remove contaminants, such as lead. To determine if your home plumbing contains lead, request a free lead-in-water test kit online at www.leadline.org. To learn more about Portland’s water quality, view our Annual Drinking Water Quality Report and Triannual Water Quality Reports.
When selecting a filter, it is important to know that not all filters are the same. Read the packaging carefully and only purchase certified filters.
- 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.
Do not 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 have been certified for lead reduction.
A variety of filters exist to meet your needs. These include pour-through pitchers/carafes, faucet mount filters, counter top or under sink filters, showerhead filters, and refrigerator filters.
Point-of-use (POU) filters treat water only where/when you need it, such as at your kitchen sink or refrigerator. POU 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. POU filters are a good choice when you want to remove contaminants that originate in your home plumbing, such as lead.
Point-of-entry (POE) filters treat all water that enters the home, including toilet water, bath water, laundry water, and in some cases water at outside spigots. POE filters may be more expensive, and will not address issues in the plumbing that are located after the filter, such as lead solder. If you have a POE filter that removes chlorine and sodium hydroxide, you are removing the disinfectant and pH adjustment in the water. This could lead to bacterial growth and corrosion of home plumbing.
Filters are available for purchase online and at hardware stores, grocery stores, and other retailers.
The NSF/ANSI Standard 177 is for showerheads that claim to reduce free chlorine. Since Portland uses chloramine (chlorine + ammonia) and not free chlorine, filters with the NSF/ANSI 177 standard may not work effectively. Some certified showerheads on the market with granular activated carbon claim to also reduce chloramine. Customers may have success with vitamin C showerhead filters, but these are not certified.
Choose one of the following 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.
Because filter cartridges collect Cryptosporidium, it is recommended that they are replaced by a person that is not immuno-compromised while wearing gloves. Follow the manufacturer's recommended filter cartridge replacement schedule. Lear more about crypto and home water filtration at the CDC's Filtering Tap Water page.
Maintenance and Cost
If filters are 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. Unmaintained filters can also harbor bacteria. Many filters have a device that indicates when to change the filter.
Certified water filters start around $20 dollars, with replacement filters being less expensive than the initial device. Filtration pitchers and faucet mount 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.
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, call the Portland Water Bureau Water Line at 503-823-7525.
If you have lead in your plumbing, run your water for 30 seconds to 2 minutes to flush the lead out if the water has not been used for several hours or overnight. Flushing your faucet will also address taste and odor issues if you have older iron pipes. To remove chlorine taste and odor, add slices of lemon 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 1 minute will also disable Cryptosporidium cysts.
Water Quality Questions or Concerns
Visit our Water Quality FAQ or contact the Portland Water Bureau Water Quality Line at 503-823-7525, Monday through Friday, 8:30 am to 4:30 pm, or email WBWaterLine@portlandoregon.gov.