Sediment Water Filtration: What is It, and How Does It Work?

[Jessica Kalvaitis]

Seeing cloudy or discolored water coming from your tap can be alarming, but it is usually a problem that can be solved with a sediment filter. In many homes, especially those with well water or older plumbing, sediment filtration plays a crucial yet often underappreciated role in maintaining optimal household water quality and protecting downstream plumbing and appliances. But how does sediment filtration work, and what exactly does it remove from water? Is it safe to drink water with sediment, and how do you check what types may be present? This guide answers these and other common questions.

Understanding Sediment in Drinking Water​

Before breaking down the mechanics of sediment filtration, it is important to understand what sediment is and how it gets into household water in the first place.

What is Sediment?​

Sediment is a general term for any undissolved particulate matter in drinking water. It can comprise sand, silt, dirt, clay, rust, mineral deposits, biofilm, organic materials, and other debris. These solids vary in shape and size and may be visible or invisible to the naked eye. Depending on their size and concentration, they can make the water appear hazy, cloudy, milky, murky, or muddy, and give it a gritty, unpleasant taste and feel.

How Does Sediment Get into Drinking Water?​

Some common reasons for suspended solids in drinking water include:

• Aging, corroded plumbing infrastructure: As water travels through public water distribution networks or household plumbing systems, interior rust flakes, fragments of piping, and other debris can leach into the water that reaches your faucets and fixtures.
• Structural intrusions and disturbances: Breaks in city water mains can draw dirt and debris from surrounding soil into the treated water. Similarly, high-flow water conditions, such as firefighting activities, system tests or maintenance, or construction, can stir up particles already in public supply lines and send them to your home.
• Compromised well systems: In well systems with damaged screens, casings, or seals, large amounts of sediment may enter the water supply directly through flooding and stormwater runoff from eroded soil, construction and mining activities, agricultural fields, woodlands, and other sources.

How Does Sediment Filtration Work?​

Sediment filtration is one of the simplest and most essential forms of water treatment. It leverages particle size and water flow to remove particulate matter from your home’s water supply. A sediment filter typically consists of a plastic housing surrounded by the filter medium. This filter medium can be made from a variety of materials, including paper, ceramic, acrylic fiber, glass fiber, polyester, polypropylene, spun cellulose, or rayon.

The Sediment Filtration Process​

Sediment filters work by using a mesh barrier, screen, or porous material to physically block solid particles from infiltrating your water supply. External pressure forces the incoming water through the filter medium, which is designed to capture particulates of specific sizes (also known as the filter’s micron rating). Tiny holes or pores in the filter material catch and retain the targeted particles, while water flows through to the other side of the filter. You can picture the process as a screen door that lets fresh air into your home while keeping out bugs, leaves, and other undesirable debris.

Some sediment filters use an expansive surface area to catch more solids. These trapped particles are held on the filter’s outer surface, where they can accumulate and form what’s commonly known as a “cake layer.” This layer often has finer pores than the original filter media, allowing it to capture smaller particles, therefore improving filtration performance. Other sediment filters use a depth gradient to filter out suspended particles. These force water through thick layers of filter media that become increasingly tight as the water nears the core, filtering out smaller and smaller particulate matter along the way.

Once the sediment has been captured, filtered water emerges on the “clean” side of the filter and continues to its next destination. This may be household plumbing, a pump, or another filter in the water treatment system.

What Sediment Water Filters Remove and Don’t Remove​

Contaminants Removed By Sediment Filtration​

A sediment filter removes all particulate matter in drinking water that is insoluble, suspended, and larger than the filter’s pore size. This can include particles of:

• Sand and silt
• Dirt and grit
• Small rocks and clay
• Rust, metal shavings, and bits of pipe material
• Organic matter like leaves, decaying plant debris, and insect and animal waste

In addition to visible particulates, sediment filtration can remove cloudiness (turbidity) and discoloration from water. Sediment filters may also be used after drinking water filtration processes that convert dissolved iron, manganese, or hydrogen sulfide into solid particles that the filter can then capture and remove.

Contaminants Not Removed By Sediment Filtration​

Sediment filters generally do not remove contaminants like:

• Microorganisms, such as bacteria and viruses
• Dissolved heavy metals, including lead, copper, and arsenic
• Chemicals, including chlorine, pesticides, and volatile organic compounds (VOCs)
• Dissolved minerals like calcium and magnesium
• Dissolved particulate matter

The filters’ pores usually aren’t small enough to catch these impurities, allowing them to pass into the “filtered” water stream. This is why sediment filters are best used as prefilters within a more comprehensive setup to help further decontaminate the water and protect downstream filters, plumbing, and appliances from clogging.

How Sediment Filters Are Used With Other Drinking Water Treatment Methods​

Sediment filtration is often the first line of defense against unwanted particulates in drinking water. Because of this, sediment filters are typically used in conjunction with other drinking water treatment processes, including:

Reverse Osmosis​

Reverse osmosis (RO) systems purify water by passing it through a semipermeable membrane that reduces a broad range of dissolved contaminants. A sediment filter is usually installed before this RO membrane to remove particulate matter that could clog the flow restrictor that pressurizes the membrane and controls the RO system’s recovery rate. It also serves as a pretreatment stage to eliminate larger particles that the RO membrane can’t remove.

Learn more: What Is Reverse Osmosis and How Does It Work? | How Prefiltration Helps Protect Reverse Osmosis Membranes | How to Install a Reverse Osmosis System (DIY Guide)

UV Water Disinfection​

Sediment prefiltration is also important for ultraviolet (UV) purification systems. These systems use UV light to destroy potentially harmful microorganisms, including bacteria and viruses. However, suspended particulate matter in the water can block, scatter, or absorb UV rays, shielding microbes from being neutralized. A sediment filter is often used to remove the particulates so that the UV light can penetrate the target contaminants and disinfect the water more effectively.

Learn more: How UV Systems Work and Why You Need One for Your Home | How to Remove Bacteria, Viruses, and Parasites from Tap Water

Carbon Filtration​

Carbon filters are particularly effective at reducing chemical tastes and odors. But while they remove some sediments, large quantities can clog the carbon media, reduce water flow, and drastically shorten its lifespan. A dedicated sediment filter installed upstream from the carbon helps extend the carbon’s useful life, improve its filtration performance, and maintain adequate water pressure.

Learn more: Activated Carbon Filters: What Do They Remove from Water? | A Guide to Coconut Shell Activated Carbon in Water Filters

Whole-House Filtration​

In a whole-house system, a sediment prefilter offers comprehensive protection from particulate matter in drinking water. If allowed to flow through your home’s plumbing, sediment may build up and eventually clog pipes. It may also affect appliances such as water heaters, dishwashers, and laundry machines, often reducing their efficiency and shortening their lifespans. Faucets, toilets, and showerheads may lose water pressure and may require costly repairs. A sediment filter ensures all the water flowing through your home is free of physical debris, reducing clogging in plumbing and appliances and discoloration of your fixtures and tiles.

Learn more: How Do Whole Home Water Filters Work? | Whole-House Water System Installation Guide

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