What Are Whole-House Backwash Filters and How Do They Work?

Updated on:
October 23, 2023

Whole-house backwash filters are a type of filtration system equipped with large tanks and special filter media that self-renew through a backwashing cycle. Unlike cartridge-style water filters that require frequent replacements, backwashing filter systems operate by reversing the water flow to rinse and cleanse the filter media of contaminants. 

Backwashing whole-house filters have been around for a while, but they got a bad rap due to their water-wasting design. Many people find them less user-friendly than simple cartridge-style filters. However, when you need an effective whole-house water filter, backwash systems have their place.

In this detailed guide, I’ve broken down the essentials of whole-house backwash water filters and how they work so you can experience the amazing features they offer. 

Quick Summary

  • Backwash whole-house filters employ a rejuvenation cycle to refresh the filter media and expel trapped contaminants.
  • Backwash filters offer greater flexibility when it comes to selecting filter media, allowing for the effective removal of specific contaminants.
  • While the water drainage from backwash filters may not be environmentally friendly, it can be recycled for other beneficial purposes.

Whole-House Backwash Filter Components

Here are the main components of backwash whole-house filters. 

  • Control valve: A control valve is the brain of the whole house filter as it regulates the flow rates and backwash and rinsing cycle. It requires a constant power supply to run. 
  • Tank: Unlike cartridge-style filters, which have multiple canisters, a backwash filter has one large tank containing the filter bed, or media. Inside the tank is a distributor tube, which water travels up and down.
  • Filter media: This is a single or combination of chemical substances that attract and absorb harmful contaminants from your water supply. 

How Whole-House Backwashing Filters Work

The working of backwash whole-house filters is fairly simple. Here are three easy steps that best describe the complete process. 

Step 1: Normal service cycle

During normal service, the water flows through the mineral tank (large filter tank) from top to bottom, contaminants getting trapped inside the filter media as it goes. The filtered water then rides the distributor tube to be used inside the home. 

However, the devil’s in the details. The high-pressure water enters through the inlet and permeates layers of air, filtration media, and gravel, which together trap contaminants.

When water reaches the end, it moves upward through the main distributor tube. After some time, the filtration media gets overly saturated and stops trapping contaminants. This is where the electronic valve initiates the backwash cycle and rejuvenates the filter media.

Inside the backwash filter (Pinterest)

Step 2: Backwash cycle 

The backwash cycle simply repeats the process in step one but in reverse order. Water is pumped through the main distributor tube and starts rising from bottom to top, absorbing all the nasty contaminants. 

The water flushes any residual sediment or organic matter down the drain line. Finally, the dirty water is pumped out of the drain valve. The whole process takes 10 to 20 minutes. 

Reverse water flow in the backwash cycle 

Step 3: Rinse cycle 

After completing the backwash cycle, the control valve again reverses the flow (normal direction), and the filter media starts to settle down. The media bed is rinsed properly, and the air is recaptured in the tank. Mind you, this water is also washed down the drain, i.e., wasted. However, the drained water can be redirected to the garden or other areas.

Once completed, the control valve closes the drain valve again and opens the supply to the house. The filtration media is fresh and rejuvenated, ready to trap harmful contaminants. Finally, the whole-house filter is back in action. 

During the backwash process, the main water supply is either cut off or diverted using a bypass valve so you may have access to the (unfiltered) water for emergencies.

Backwashing Filters and Flow Rate 

The whole backwash filter cycle runs automatically. However, keeping an eye on the flow rate can help you maintain the filter. You can usually monitor the flow rate on the electronic control valve display. 

A sufficient flow rate during the backwash cycle is necessary for proper cleansing of the filter media. Typically, 5 gallons per minute (gpm) is the optimal flow rate for a large tank filled with carbon media. For a denser media, like KDF, a 15 gpm backwash flow rate is recommended. 

As for normal service, a 3 gpm flow rate is optimal. It gives sufficient time for water and filter media to come in contact, resulting in cleaner water. 

Higher flow rates during the normal service cycle may result in channeling, which is what happens when water finds the path of least resistance and makes channels (small tunnels) inside the filtration media, leading to inefficient filtration. Contact the manufacturer if you experience such a thing. 

How Often Should You Backwash a Whole-House Filter?

Most modern whole-house backwashing filters come with an automatic backwashing system and require no effort on your part. Just set the timer for a specific time, preferably when you least require the filtered water. 

Another way is to manually backwash the system. To do this, install pressure gauges before and after the water filter. If the outlet pressure drops below 15 psi, press the relevant button on the control valve to start the backwash cycle. You can find the recommended backwashing times in the table below.

ApplicationFilter mediumBackwash time
SedimentNEXT Sand/Katalox LightEvery 7–28 days: 10–16 min
IronKDF-85Every 3 days: 10–16 min
Iron/chlorine/ sulfurGranular activated carbon/catalytic carbonEvery 14–28 days: 10–16 min
ArsenicNano titanium oxideEvery 14–21 days: 10 min
pH neutralizingCalcite/magnesium oxideEvery 3–7 days: 10–16 min

Table 1: Recommended backwash cycle intervals.

How Long Does a Backwash Filter Last?

A typical backwashing whole-house water filter can last between four and ten years, depending on its specifications and the condition of the valve and tank after prolonged use. It requires virtually no maintenance since the rejuvenation of the filter media is carried out automatically at preset intervals by the electronic control valve. 

Once the filter reaches its limit after several years, you just need to replace it with fresh media, and it will be good to go. In this regard, the backwashing filter one-ups the ordinary cartridge-style filter, which requires more-frequent replacement.  

The specific lifespan of your filter media will depend on the type of media, frequency of the backwash cycle, and nature of the contaminants in your water. Some filtration media, like sand and catalytic carbon, require a change every two to four years, while others, like Katalox-Light, may last seven to ten years. 

Types of Filter Media Used in Backwash Water Filters 

Just as there are many types of filters, there are also many types of filter media, and each works best when used for its intended purpose. Some work remarkably well against suspended particles, like fine sediment and silt, while others are built to trap dissolved contaminants like chlorine, sulfur, and iron. 

It’s best to have your water supply tested and then choose the right media for your whole-house system. Here is a brief explanation of commonly used media you’ll find in a backwashing filter system. 

Granular activated carbon (GAC) and catalytic carbon

Carbon is the most common filtration material used in water filtration. Not only does it remove chemical contaminants, but it can also improve the taste and odor of water. These days, high-grade activated carbon is extracted from coconut shells, which is a pretty effective organic solution. 

The performance of activated carbon can improve through some chemical processes. This creates a catalytic coating on granular activated carbon (GAC), greatly enhancing its filtration capabilities. However, it’s one of the more expensive options.

Centaur is the primary brand that manufactures GAC and catalytic carbon. Carbon is particularly useful at cleansing water of sediment, chlorine and chloramine, iron, and hydrogen sulfide (rotten egg smell).

Manganese oxide, Greensand, and Filox-R

Manganese, when oxidized, is effective against many common impurities in water. It’s available under the brand name Greensand, which is actually glauconite (iron potassium phyllosilicate) coated with manganese oxide. 

Another variety, Filox-R, is also used in backwash filters and is 85% manganese dioxide. Filox is a denser mineral and requires a high flow rate during the backwash cycle, so it might not be suitable for well water systems that run on lower pressure than the city supply. However, it’s good at removing a few iron, manganese, and hydrogen sulfide. 


Birm (Burgess Iron Removal Method) is a water treatment product by Clack Corporation. It’s a combination of salts and aluminum silicate. It’s a granular black substance similar to GAC. 

The thing you need to keep in mind is that it’s pH sensitive and works only if your water supply is between 6.8–9.0 pH. It also doesn’t work in the presence of hydrogen sulfide and tannins. So, you may need a pretreatment system for it to work properly. 

Since it’s lighter media, it doesn’t require a higher flow rate for backwash and is ideal for private well systems.


KDF (Kinetic Degradation Fluxion) is a pretty common filter media brand, and you might have heard companies boasting about its antimicrobial filtration. Its effectiveness comes from the combination of high-grade copper and zinc particles. KDF can filter a host of contaminants:

  • Heavy metals
  • Iron
  • Chlorine 
  • Hydrogen sulfide
  • Microorganisms
  • Bacteria

Anthracite, sand, and Filter-Ag

Anthracite is a type of hard coal that effectively treats contaminated water. It is frequently used alongside sand and garnet (a mineral) granular particle as a sediment filter. 

Ordinary sand consists of granular silica particles, providing a cost-effective solution for removing sediment and debris from water. Similarly, Filter-Ag, a product made from non-hydrous silicon dioxide, is effective against sediment and suspended organic particles. 

Zeolite/Micro Z 

Zeolite is a mineral used for sediment filters and marketed under the brand Micro Z. Zeolite has amazing filtration and medicinal properties. It’s best used for trapping micro-sediments within 2 to 10 micron size.

Backwash Filter Troubleshooting

If you encounter diminishing flow rates or notice poor water quality, here are some troubleshooting steps you can take:

  1. See if the power supply is plugged in properly and restart the whole system.
  2. Run the backwash cycle manually and see if it’s working properly. 
  3. Check the filter media expiration date and replace it if necessary. 
  4. Check for leakage around valves and pipes and tighten any loose connections.  

Pros and Cons of a Backwashing Water Filter

Backwashing whole-house water filters are an excellent choice for an efficient water treatment system in your home. Here are some major benefits you can expect from these water filters. 


  • Improved taste, odor, and overall water quality
  • Longer filter media lifespan with minimal maintenance
  • Cost-effective in the long run with fewer replacements
  • Customizable to match your specific water treatment needs


Like every water filter system, this one also has its shortcomings. Here are some inherent flaws in the whole-house backwashing filter.

  • Excess water wastage
  • Higher water consumption and bills
  • Costly installation
  • Increased electricity usage
  • Noisy

Final Thoughts

Whole-house backwashing filters might not be everyone’s cup of tea, but they can be a solid alternative to cartridge-style whole-house filters. Remembering the details I’ve talked about will help you pick the right filter and even get the hang of that manual backwash thing if you ever need it.

I hope this article helped you understand backwashing filters and how they work. If you have any follow-up questions, leave a comment below. Backwashing is one of the oldest types of modern filtration, time-tested and approved…mostly. For more information about whole-house water filtration, read my reviews of the best whole-house water filters on the market

If you’re interested in learning more about whole-house filters, take a look at the guides and reviews we’ve provided below.

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