How to Filter Out Colloidal Clay From Well Water

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Things You'll Need

  • Coagulant

  • Nanofilter

Cloudy water is a sign of colloidal clay particles in your well.
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Filtering colloidal clay from your water can be a difficult feat to achieve. The extremely fine particles can lead to cloudy well water and cannot be removed with standard filters. Typical sediment filters of 30 microns will probably not be adequate. Colloidal clay usually must be coagulated before filtering, which aggregates the clay particles so they can then be strained through a standard filter. Another option is the use of ultrafiltration or nanofiltration, which requires filters smaller than one micron. A combination of these two options may be necessary. Professional assistance will ensure the most economic and adequate approach.


Step 1

Schedule an inspection of your well, and have the inspector look for surface water infiltration if your well is deep. Sealing the well 10 to 20 feet below the level of infiltration may help reduce clay levels significantly, but should not be pursued if water production will be limited as a result. An expert consultation is highly advised.

Step 2

Set up a secondary point-of-entry filter with less than one micron, called nanofiltration or ultrafiltration. Check for cloudiness to determine whether the colloidal clay has been removed. Set up a series of parallel nanofilters to improve their effectiveness and reduce the need for filter changes.


Step 3

Add a coagulant such as aluminum sulfate to your well water at a rate of 1/8 teaspoon for each gallon of water if the micron filter alone is not adequate to remove the clay. Ferric chloride and other coagulants are also available for use. Coagulants, also called flocculants, work by reducing negatives charges of particles, causing them to aggregate into larger groupings that can be caught in a filter. Pass the water through a particle filter prior to drinking.


Since their effects are affected by pH and other factors, you may want to test the coagulants before applying them. Set up a series of jars filled with your well water, and add each proposed coagulant type to see how well the material condenses and congeals in each jar. Consulting a water treatment expert can help you select the best system for your well water.


The World Health Organization advises that residential flocculation and clay removal is possible, but cannot be optimized without proper equipment and training in chemical application. The organization does not recommend the method for home application.



Carly Fiske

Carly Fiske has been writing professionally since 2009. She writes for websites including, and Fiske holds a Bachelor of Arts in cultural anthropology from the University of Redlands.