My well water has a nitrate level between 20-30 ppm determined by API liquid kit and a commercial water lab. I placed the nitro-absorb resin bag into my filter last Thursday and this morning the nitrate level in the tank fell to 5 ppm. I am impressed. I did not think the resin would be that effective. It is “rechargeable “ by soaking the resin bag in salt water. The salt releases nitrate from the resin.