iSpring FA15 RO Alkaline Remineralization Cartridge

iSpring FA15 is a high-quality inline alkaline water filter and it comes in two versions, a new upgraded version, and an older version.

In this review, we look at the new iSpring FA15 version which comes with a few upgrades that make it much better than its older version and most other alkaline water filters in the market today.

The first thing that makes this upgraded iSpring FA15 model stand out is the set of media that it comes with. It’s a 3-lay mineralization filter cartridge made up of red mineral stone, calcite and corosex.

The purified RO water first goes through the mineral stone side (red), then moves through the calcite media side (white/clear) where it exits towards the RO faucet.

As the RO water passes through the filter, the three media restore back the lost minerals which include calcium, potassium, magnesium and sodium ions which in turn improve the pH level of the RO water.

The filter is capable of raising the pH level by 0.5 to 1.2 which makes it quite effective for use in areas where the source water has a very low pH level.

All the media and material used in making this iSpring FA15 filter are all-natural and FDA grade hence they are not only safe. They will leave no residues behind or further contaminate the water as the synthetic alkaline filters do.

The updated FA15 alkaline filter can work with any under-sink RO system. Unlike the older version, this one features a very secure push-fit quick connection for quick installation or replacement at the end of your RO system as the last stage.

You just need to screw the push-in connector on each end then attach a ¼” water tube on both sides. However, the flow direction arrow is not that well labeled like in the older FA15 alkaline filter but it can be installed in either direction.

The filter does not affect the normal flow rate of water and considering that it’s an inline filter, you won’t need to buy housing. It can last from 6 to 8 months depending on the pH level of your RO water.

Price & Rating

ProductiSpring FA15 RO Alkaline Remineralization Cartridge
Rating3.7 out of 5 stars (More than 62 reviews)
Recommended price24.38 USD (Check the latest price at

Product Specification

Dimensions9 3/4″ x 2 7/8″
Service life 6 months or 1500 gallons
CompatibleRO systems & Inline filters


What is the direction for water flow?

You may not find the direction for the water flow as you can install it in any direction, however, many customers installed it with the water inlet at the red mineral stones side and exit on the side with the white crystals or calcite.

How many mg/L of each mineral in the final drinking water produces with this remineralization filter?

This remineralization filter balances the pH in the RO water, it means just a little amount of minerals will be added to the RO water. If you want to know the exact amount of mg/L of calcium/magnesium in the final drinking water, your water should be tested in a lab test.

Does this ALK filter come with the hardware & connectors for installation?

No, you have to by the connectors and hardware for installation separately.

Image Gallery

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