Color Changing DI cartridge. Just unscrew the housing, take out the old one and insert the new one.
Ready to use. No rinsing required. Comes filled with color changing DI resin.
Formula to estimate when the DI resin needs replacing explained below:
Each DI Cartridge has a 260 grain capacity:
Step 1) RO water TDS divided by 17.1 = Grain Usage
Step 2) 260 grains divided by Grain Usage = Estimated RO/DI Gallons until resin is depleted
Example: If the RO water measures 6 TDS:
Step 1) 6 divided by 17.1 = 0.35 grains
Step 2) 260 divided by .35 = 743-gallons expected
Melev's Tip: As the DI resin changes color, it's still important to measure the TDS to actually know what the output water reads. I have personally seen cartridges that are only half orange output high TDS readings even though all the resin didn't change color as one might expect. Once, a cartridge was still about 50% black but the output was measuring 40 TDS, so it had to be replaced. Other times I've had the entire cartridge turn orange yet the TDS coming out was still 0. The color-change is only a visual indicator; a TDS meter is key to knowing what is really going on. Be sure to watch my TDS Creep video in this article: http://www.reefaddicts.com/content.php/182-RO-DI-TDS-Creep-is-it-worthy-of-concern