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iSpring FD15 DI Deionization RO Replacement Filter Review

If you want zero TDS water but don’t want to get a whole new reverse osmosis system, then this FD15 Deionization filter might just be the right fit for you.

This is a filter for RO DiIonization systems which is added as the 6th stage post filter. The FD15 functions by using a process called deionization or ion exchange technology.

The ion exchange resin media inside the filter exchanges positive hydrogen and negative hydroxyl ions for the positive and negative ions of the contaminants in the water.

Therefore, all the positive ions like calcium, magnesium, and potassium, exchange places with hydrogen ions while the negative ions such as iodine are replaced by hydroxyl ions.

This process is super-efficient at removing even the most difficult minerals and finest contaminants in the water.

This is because all the positive and negative ions of contaminants in the filtered water are displaced by the active hydrogen and hydroxyl ions on the ion exchange DI resins. As a result, you get highly purified water with zero TDS.

It’s a great option if you have an RO system already installed and you want to completely remove dissolved contaminants and minerals in your RO water. It’s also very effective at softening the water level hardness.

In terms of installing the FD15 to your RO DI system, you won’t break a sweat as it’s just a matter of fitting it after the 5th stage carbon post filter.

It uses ¼” fitting which means it will fit almost any standard RO DI system and the housing is clear for an easier view of the media status.

The best part about this iSpring DI filter is that it’s refillable. You can actually open it and then fill it up easily with another media.

In other words, it simply provides a much more efficient and reliable way of removing all TDS, minerals and other small amounts of residual impurities that may have slipped through the RO membrane and post carbon filter.


  • Reduces TDS value to almost zero
  • Filtered water is great for drinking and aquarium use
  • Easy and quick to install
  • Fits almost any RO DI system
  • You can refill the media


  • Requires a ¼” fitting which is not included

Price & Rating

The iSpring FD15 DI Deionization RO Replacement Filter Review is rated 3.5* out of 5* and reviewed by 35 verified purchase customers and it is listed at the price of 26.29$.

ProductiSpring FD15 DI Deionization RO Replacement Filter Review
Rating3.5 out of 5 stars
Recommended price(Check the latest price at Amazon.com)


Can I refill and replace the media inside the filter?

Yes, you can refill the media.

Should I use this filter for a drinking water RO system?

No, you shouldn’t. The DI resin media in the filter can give the RO water an odor or flavor. It is normally used for saltwater or freshwater aquariums.

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iSpring FD15 DI Deionization Filter

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