What Are Green Sand Filters?

Greensand is the name commonly applied to a sandy rock or sediment containing a high percentage of the mineral glauconite. Glauconite ((K,Na)(Fe3+, Al,Mg)2(Si, Al)4O10 (OH)2) is a greenish-black to blue-green mineral which forms in shallow marine sedimentary deposits. Greensand media has been incorporated into countless filters due to its flexibility and efficient iron and manganese removal in both the municipal and industrial markets. This user-friendly media is commonly found in horizontal pressure filters, vertical pressure filters and in gravity filters where iron is the primary contaminant to be removed. Greensand Media is versatile, able to also extract manganese, hydrogen sulfide, radium and arsenic contaminants as well, making it a popular filtration option. The greensand filter media has a special coating of manganese oxide, which oxidizes iron, manganese and iron in the water upon contact with the filter media.

Greensand filters require a type of potassium permanganate to regenerate and clean the greensand filter media.


Iron and manganese are metals often found dissolved in water. Iron and manganese cause stains when exposed to
air in the laundry, bath, etc. by oxidizing or “rusting.” The greensand filter media oxidizes dissolved iron and
manganese on contact as the water flows through the greensand filter which causes these elements to precipitate
(or form solids) in the bed of the filter.

The iron filter backwashes these small particles to drain every few days in the middle of the night (or some other
preset time), thereby cleaning and restoring the filter media. To provide the oxidizing power to precipitate these
metals, the filter is automatically cleaned and restored with potassium permanganate (a purple liquid) during each
backwash cycle.

Potassium permanganate is a powerful oxidizer and, similar to chlorine, can cause skin irritation or burns if direct
contact were to occur. But, no permanganate is added to the filtered water. The permanganate is only used to
backwash and clean the greensand filter media. A special rinse cycle makes sure the filter bed is free of any
permanganate residual

While greensand filters will remove up to 5 PPM of hydrogen sulfide, in some cases the odor can be coming from
conditions that exist after the water enters the plumbing. For instance, water heaters often have decaying anode
rods that create hydrogen sulfide gas, so that even if the water entering the water heater is clean and odor-free,
you can still have an odor problem.

It is important to identify the source of the odor and to verify that it is in the cold water also, which would indicate
that all the incoming water has an odor. In many cases, a thorough sanitizing of the household plumbing with
chlorine is recommended after installation.

Yes, these systems work great to remove manganese, both dissolved and oxidized. For manganese removal, the
greensand filters are an excellent option, as many iron filters do a good job of removing iron but do not do a good
job at removing manganese.

Once every one to three months depending on how often the iron filter is set to backwash, a few pounds of dry
potassium permanganate powder is added to the little solution tank. Once a year there is some general
maintenance that should be done to the iron filter and permanganate solution tank, which takes about one hour.
No special tools are required.

The filter media will last for 4 to 8 years depending on usage and conditions. It is easily replaced.