What Is a Sediment Filter and How Does It Work?

Posted by
John Woodard on December 04, 2023

A sediment filter traps and removes debris from stormwater runoff, rust flecks, suspended solids, and other particulates that contaminate water. The debris caught by a sediment filter can age pipes and leave your water discolored and unappetizing. Sediment build-up can also wreak havoc on appliances, clogging up valves and fixtures and ruining hot water heaters. It prevents filtration systems like reverse osmosis and ultraviolet purification from operating efficiently as well. Sediment filters keep your water clear and are an integral component of the water filtration process. In this article, you can learn answers to common questions regarding sediment water filtration.

What is a sediment filter? 

sediment filter captures and removes particulate matter like dirt and debris from your water. Sediment is a generic term for all particulate matter in your water that is not liquid. One common example of sediment in water is rust flakes from corroded galvanized plumbing. Rainwater can carry silt, clay, soil, and grains of sand into your well groundwater supply. Flow changes in your water main can also transport sediment to your home. The sediment filter is the first line of defense against this dirt and debris. It prohibits all this solid particulate from entering your water supply and impeding the performance of your water filtration systems

How does a sediment filter work?

Sediment filters work through a process called mechanical filtration. Mechanical filtration physically blocks unwanted particulate matter from infiltrating your water supply. You can think of mechanical filters as a screen door. You want the refreshing breeze to flow through your home, but you do not want bugs or leaves blowing in with it. In this example, the screen door acts as a mechanical filter. Sediment filters allow water to flow into your home while capturing the dirt and sand the water is carrying. Sediment filters are the net that catches the particulate matter traveling in your water. 

Some sediment filters use expansive surface areas to catch large amounts of debris. Other sediment filters use a depth gradient to filter out suspended particles. These force water through thick walls of filter media that become increasingly tight as the water nears the core, filtering out smaller and smaller particulate matter along the way. 

Where are sediment filters used?

Sediment filters are used across a wide array of applications. Restaurants and coffee shops use sediment prefilters to ensure the quality of their food and beverages. Whole house filtration systems employ sediment filtration to eliminate particulate matter from entering your faucets and showers and to protect the lifespan of other filters. Your pool filter cartridges are a form of sediment filter, blocking dirt and clay from muddying your pristine swimming water. Any instance in which clean water is imperative, you will likely find some form of sediment filter.  

What does a sediment filter remove? 

Sediment filters remove visible particulate matter, and any particles of dirt, sand, dust, and debris that can be caught by its micron-rated capacity. In addition to particulates, they can also remove cloudiness, also known as turbidity, from water. This causes water to turn yellow, orange, or brown. 

Sediment filters do not remove chemicals, heavy metals, bacteria, or dissolved particulate matter. Likewise, they do not improve the taste or smell of water. They are primarily a defensive and preservative filtration method. Sediment filters are most effective when serving as prefilters for other filtration systems. This is why sediment filtration very often works in conjunction with other filtration methods, like reverse osmosis or ultraviolet purification.  

What are sediment filters used for? 

Sediment filters are used in conjunction with practically every water treatment system. Anytime water has dirt, debris, or fine particulate, a sediment filter is necessary. Sediment filters are also vital in ensuring other filters and water filtration equipment can operate efficiently. 

Reverse osmosis

Reverse osmosis (RO) systems always utilize a sediment pre-filter. Reverse osmosis purifies water by passing it through a semipermeable membrane that eliminates metals, salts, and dissolved solids. The sediment filter functions as pretreatment and protection for the RO system. The reverse osmosis membrane handily rejects particulate matter, but the water rejected by the membrane drains through a tiny flow restrictor. This flow restrictor pressurizes the RO membrane and controls the recovery rate of the reverse osmosis system. The sediment prefilter on an RO system protects the flow restrictor from clogging rather than protecting the membrane itself. 

Learn more: What is a reverse osmosis system and how does it work?

Ultraviolet purification

Ultraviolet (UV) purification systems also require sediment filters. UV purification systems neutralize bacteria, parasites, and microorganisms via germicidal ultraviolet wavelengths. UV light damages the DNA of these living organisms, rendering them unable to reproduce. These systems offer an effective filtration method for microbiologically unsafe water. However, cloudiness in the water diminishes the efficacy of UV. Water turbidity is difficult for the UV radiation to penetrate, and bacteria can hide from the wavelengths behind particulate matter. As a result, a 5-micron sediment filter is needed to treat water running through a UV system.

Learn more: What is a UV water purifier and how does it work?

Carbon filters

Carbon filters are known for their ability to restore water’s fresh taste by removing chlorine and chloramines. While carbon can also filter out sediment, dirt particles can clog up the carbon and quickly exhaust the filter media. If carbon filters are forced to filter out large quantities of sediment, their lifespans shorten drastically. Sediment filters are far cheaper to replace than carbon filters, so it is wise to install a sediment prefilter to prolong the life of your carbon blocks. If you are using a whole-house carbon filtration system, investing in a sediment pre-filter will save you significant money, ensure your carbon filters can operate at peak performance, and maintain adequate water pressure in your home.  

Learn more: Activated carbon filters 101

Whole house sediment filtration

whole house sediment filtration application can save you precious money. Sediment can be an absolute detriment to household appliances. If allowed to flow through your home’s pipes, sediment will eventually cause pipes to clog, slowing the water pressure and flow in your home. Sediment damages dishwashers and washing machines, often shortening their lifespan significantly. Water heaters become clogged and malfunction if sediment accumulates in them, reducing the unit’s efficiency, capacity, and overall life expectancy. Faucets, toilets, and showerheads will lose water pressure with extended sediment build-up. These are costly and avoidable repairs. Even if you don’t use any other type of filtration system, sediment filters will protect and prolong the life of your household appliances. 

If you use a private well as your water source, whole house sediment filtration is advisable.  Groundwater is likely to harbor a larger quantity of sediment than city water supplies. Stormwater and flooding can usher unwanted debris into your well. The semipermeable rocks that water passes through before reaching aquifers can deposit silt and sand into your water supply. Sediment filters provide necessary purification for those who depend upon well water for their household and set the stage for all other whole house or point-of-use filtration systems. 

Learn more: What is a whole house water filter? | How to install a whole house water filter for well water

Types of sediment filters

All sediment filters are designed to do the same job: collect solid debris and particulate from the water. However, there are several configurations of sediment filter cartridges on the market. The most popular variations include pleated, melt-blown, string-wound, bag, and spin-down filters.

Pleated filters 

Pleated sediment filters are accordion-shaped designs made of thin sheets of filter media like polyester or polypropylene. They are also referred to as surface filters. The volume of pleated folds gives this style of filter considerably more surface area than other types of sediment filters. Pleated filters utilize their extensive surface areas to trap sediment particulate. As the filter’s pleats take on dirt, a layer is formed on the filter that amplifies the filter’s efficiency. The dirt trapped in the filter becomes part of the mechanical filtration process. Pleated filters work optimally when filtering out larger particulate. Their broad surface area means they can be manufactured to effectively filter particulate of uniform micron size. Pleated filters also have the advantage of being washable and reusable.  

Melt-blown filters 

Melt-blown filters utilize depth gradients to remove sediment from water. These filters are made by blowing high-velocity gas through molten polymer, which forms intricately layered fibers. The inner core of melt-blown filters is denser than the outer core, so as water is processed through the filter walls, the filter can trap increasingly finer particulate. The graded density of melt-blown filters, also known as spun filters, can filter down below 10 microns. They are ideal for filtering very fine particulate. Melt-blown filters excel at filtering particulate of varying micron sizes because of their gradation.  

String-wound filters 

String-wound sediment filters are a variation of melt-blown filters. They are comprised of tightly wound cotton, polyester, or polypropylene string. This string is wrapped firmly around a core, creating a graded density that will trap particulate matter. As water travels through the layers of string, finer and finer particulate matter is removed. However, once string-wound filters become overloaded with sediment, the strings can begin to loosen and shift. This can allow debris back into the water, indicating it is time for a filter replacement. 

Bag filters 

Bag filters eliminate sediment by processing water through small permeable pores. These can range in micron size between 1 and 200. Made of polyester felt or polypropylene felt, bag filters come in a range of sizes and styles and can be manufactured in a high-density depth filter design. Sediment bag filters have a multitude of applications, from reverse osmosis prefiltration to processing chemicals, paints, resins, and solvents. 

Spin-down filters 

Spin-down filters use centrifugal force to eliminate sediment from water. Water enters the top of a spin down filter and is diverted into a clear chamber where the water is spun around. The heavier sediment is flung to the outside of the housing by centrifugal force before settling at the bottom of the chamber. Using a mesh screen, particulate anywhere from 100-15 microns is further separated from the water. These filters are designed to do the heavy lifting, like removing large chunks of dirt and debris from well water. Spin-down filters do not require disposable cartridges. When spin-down filters become full of sediment, the debris can be flushed out of the filter using a valve at the base of the filter housing. Sediment trappers are akin to spin-down filters but have the capacity to hold more sediment before requiring flushing. 

Learn more: What is a Rusco spin-down filter and how does it work?

What micron size does my sediment filter need to be?

A sediment filter’s capacity for particulate removal will be rated in microns. A micron, short for micrometer, is one-millionth of a meter in size. A sediment filter’s micron rating indicates what size particles the filter will be able to eliminate. For example, a 10-micron filter will remove everything 10 microns and larger. For perspective, a human hair is between 75 and 80 microns in size, and any particle below 35 microns will be invisible to you without a microscope. The ideal micron rating of your sediment filter will vary based upon the respective size of sediment you are seeking to eliminate from your water source. If you are prefiltering your water for a UV system, you will want to make sure your sediment filter is rated for a minimum of 5 microns. A residential RO system will also operate smoothly with a 5-micron sediment pre-filter. If you are installing a whole house sediment filtration system, you can experiment with various micron ratings until you produce the desired results.

Learn more: How many microns should your water filter be?

Filter micron ratings will be either nominal or absolute. A nominal 5-micron rating means the filter is designed to capture approximately everything five microns and above. An absolute 5-micron rating means the filter will remove over 95% of anything five microns in size. Most sediment filters have a nominal micron rating. If you would like an absolute rated micron filter to ensure a specific contaminant is removed from your water source, these options are also available. 

micron size chart

How often should I change my sediment filter? 

You should change your sediment filter every six months to one year. However, the best way to know when you’re due for a filter change is to observe your water pressure. When your pressure begins to drop, you need to change the filter. After the filter has captured enough sediment, water will struggle to pass through the filter at the same flow rate, causing water pressure to decrease. At this point, the holding capacity for the filter has been maximized and it should be changed (or cleaned if you have a pleated filter). If you do not change the filter, it will become so burdened with dirt and debris that water will altogether cease to flow through it. 
Another popular way to monitor your sediment filter’s lifespan is to install in it a clear filter housing. This way, you can watch it accumulate sediment. When you notice that the filter is caked in dirt, you know it is time to replace the filter.


If you have any additional questions, please do not hesitate to contact us.

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