What Size Micron Filter for Well Water is Best?

The micron size of a filter dictates the contaminants the filter can remove. It’s important to get the right micron size for your well water filter to prevent one of two occurrences: premature clogging or contaminants simply slipping through the filter’s pores and contaminating your water supply.

In this guide, we’ve shared everything you need to know to if you’re wondering what size micron filter you need for your well water.

📌 Key Takeaways:

  • A filter’s micron rating refers to the size of its pores. The smaller the pores, the lower the micron rating.
  • The most common micron ratings for well water filters range from sub-micron to 100-microns.
  • The best micron size for a well water filter depends on your water quality and contaminants present, your water flow rate, and your preferred filter type.
  • In some cases, you may need to treat your well water with multiple filters with different micron ratings.

🔎 What Are Filter Microns?

A micron is a measurement of the size of something physical. In this case, microns help us to measure the size of contaminants in water and the size of a filter’s pores.

💡 Microns are tiny. A single micron is 1/1,000,000 of a meter. This makes microns ideal for measuring super-small contaminants that are invisible to the naked eye, like microorganisms, dissolved chemicals, heavy metals, and sediment.

Nominal Vs Absolute Micron Ratings

A filter’s micron rating tells you how big or small its pores are. There are two micron ratings you’ll probably read about: nominal micron ratings and absolute micron ratings.

  • Nominal ratings tell you approximately what sized impurities the filter media can trap. For instance, if a well water filter has a nominal micron rating of 5 microns, it means that the filter can remove up to 80% of all impurities that are 5 microns or bigger. But this rating doesn’t guarantee 100% contaminant removal – it just gives an indication of its capabilities.
  • Absolute ratings are more precise. If a filter has an absolute micron rating of 5 microns, it means that it can eliminate 99.9% of particles that are 5 microns or bigger. It’s super helpful to know a filter’s absolute micron rating since this is more accurate than a nominal rating.
Nominal and absolute micron rating comparison

🤔 Why Is Micron Size Important?

The micron size of a filter is important because it determines what sized particles the filter media can remove.

Let’s say your well water contains a lot of fine sand, which is about 50 microns in size.

If you bought a 100 micron filter, the sand particles would be small enough to slip through the filter’s pores.

But if you bought a 5 micron filter, the filter’s pores would be so small that they would become clogged instantly with sand and any other contaminant right down to 5 microns in size, affecting your water pressure and shortening the filter’s lifespan.

It’s important to get the right micron size to allow your chosen filter to effectively remove contaminants from your water without clogging too quickly.

Related: What to do when well water filter is full of sand

Cartridges with different micron size ratings

💯 Popular Well Water Filter Micron Ratings

Below, we’ve listed the micron ratings you’re most likely to come across for well water filters, in order from smallest to largest.

Sub-Micron Filtration

Sub-micron filters are the smallest-micron filters available for well water today. These filters have pores that are smaller than 1 micron in size, enabling them to remove even the tiniest contaminants, like some viruses.

1 Micron Filter

A 1 micron filter is a popular choice for people concerned about bacteria and other very fine particles in their water. 1 micron water filters are usually the final stage in a whole house well water filtration system to capture contaminants that have been missed by larger filter media.

5 Micron Filter

5 micron filters are typically the smallest sediment filters you can buy for well water, and are designed to remove small suspended particles of silt and other sediments.

25 Micron Filter

A 25 micron filter is a big step up from a 5 micron filter, and is capable of removing the majority of granular particles from well water.

50 Micron Filter

A 50 micron filter is a popular option to remove sediment that can be seen by the human eye, such as dust and fine sand particles.

100 Micron Filter

Finally, a 100 micron water filter removes larger visible water contaminants, such as chunks of rust, sand, gravel, and dirt.

Water filter micron rating contaminant removal chart

📰 How to Choose The Right Size Micron Filter For Well Water

To choose a suitable micron filter size for your well water, consider the following things:

Your Water Quality/ Contaminants

If you don’t already know which contaminants your water contains, get it tested. Your test results will tell you which contaminants you need to remove, helping you to choose the right micron size for your sediment filter or other well water filter.

water testing with tap score

The Filter Type

The type of filter you need will determine the micron ratings available for that filter.

For instance, if you’re looking for the best sediment filter for well water, there are a couple of options:

  • Pleated or surface filters, which trap contaminants on the surface of the media
  • Depth filter cartridges, which trap contaminants across the entire depth of the filter media
  • Spin-down filter cartridges, which rapidly spin water and trap contaminants in a filter screen

💡 Pleated and depth sediment filters are both examples of a cartridge-based sediment filter and have more varied micron ranges. Most spin-down sediment filters can’t usually trap contaminants smaller than 60 microns.

Aside from sediment filters, there are a few other types of filter media commonly used for well water:

  • Carbon filter cartridges, which are usually a second or third stage in a whole house water filter system, and have 0.5-5 micron pores, depending on the type of cartridge filter.
  • Ultrafiltration cartridges, which have tiny pores of 0.02 to 0.05 microns and target small contaminants like bacteria.
whole house water filter cartridges

Your Water Flow Rate

Your water flow rate is also an important factor when choosing between micron ratings for your well water filter.

The smaller the micron size, the slower the flow rate, because of the decreased pore size. If your flow rate or water pressure is already low, you may not be able to install a filter with a very low micron rating.

Number Of Filter Stages

There’s a good chance that you’ll benefit from multiple filters for your well water, each with a different micron rating.

For instance, you might need three filters in your well water filtration system:

  • A 50-micron sediment water filter to trap large, visible contaminants
  • A 5-micron whole house sediment filter to trap smaller particles
  • A 1-micron or submicron filter to remove bacteria, asbestos, and other tiny particles

Combining higher and lower micron rating filters means you can successively trap contaminants of different sizes in your water supply. Just make sure to start with the largest micron filter and work your way down until the smallest filter, to prevent large contaminants from clogging your small micron filter pores.

sediment filters

❔ What Micron Water Filter For Well Water Do I Need? FAQ

What micron water filter is best for well water?

The best micron size water filter for well water depends on the size of the contaminants in your water. Most people will benefit from multiple filter micron sizes to trap contaminants of different sizes.

Which is better 5 micron or 20 micron filter?

A 20 micron filter is best if you have sediment like fine sand in your water, while a 5 micron filter is best for removing smaller, invisible contaminants.

Is a 1 micron filter better than a 5 micron filter?

A 1 micron filter is better than a 5 micron filter if your water contains bacteria and other tiny contaminants. However, a 1 micron cartridge will clog faster than a 5 micron cartridge due to its smaller pore size.

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