IceCap Dual DI Filter Canister | Inline Polishing DI for RO/DI Water

The IceCap Dual DI Filter Canister is an inline dual-chamber deionization housing designed to polish RO water down to a true 0 TDS — the standard for pristine reef tanks, sensitive freshwater shrimp setups, and planted aquariums. Two DI cartridges in series mean the first stage takes the bulk of the load while the second stage acts as a final polisher, dramatically extending the life of your DI resin and giving you a more reliable 0 TDS reading at the outlet.

Heads up — Overweight Item: Due to size and weight, this item is not eligible for our free shipping program. Standard shipping rates apply at checkout. Local pickup is always free at our Lawrenceville GA store if you'd rather skip the shipping.

Looking for more water care? Browse our Filter Media & Cartridges, Maintenance & Water Care, and Water Testing Kits.

• Dual-stage DI — two chambers in series for longer resin life and more reliable 0 TDS output
• Refillable — reload with bulk DI resin (color-changing or mixed-bed) when exhausted
• Standard fittings — integrates with most RO/DI systems with quick-connect or threaded inputs/outputs
• Wall-mount friendly — compact, durable housing for under-sink or utility-room installs
• Suitable for both freshwater and saltwater — anywhere you need ultra-low TDS top-off or makeup water

• Where it goes: After your RO membrane, before the storage tank or float valve. Water flows in → first DI chamber → second DI chamber → out to your reservoir.
• Resin loading: Use color-changing mixed-bed DI resin (or a separate cation/anion stack) so you can visually see when each chamber is exhausted.
• Replace timing: When the first chamber's resin has changed color completely, swap it for fresh resin and rotate the second chamber forward — the polishing chamber typically lasts 2–3x longer than the first.
• TDS check: Keep a TDS meter inline at the outlet — anything > 0 means the second-stage resin is starting to break through and needs attention.
• Initial flush: When loading new resin, run a few gallons through and discard before using for top-off; this clears any fines or air pockets.

• DI resin & replacement cartridges — keep spares so you never miss a top-off
• TDS meters & water testing — verify 0 TDS at the outlet
• Reef salt mixes — pair with clean RO/DI for stable salinity
• Maintenance & water care — water conditioners, buffers, and additives

Why a dual DI vs. a single DI?
Two chambers in series means the first stage absorbs the bulk of the ions, while the second polishes anything that breaks through. You get longer resin life overall and a more reliable 0 TDS reading because there's always a "fresh" polishing chamber on the back end.

What resin should I use?
A color-changing mixed-bed DI resin is the easiest — you can see at a glance when it's exhausted. Some hobbyists run separate cation and anion resin in each chamber for even longer life.

How often do I replace the resin?
It depends on your source water TDS, RO membrane efficiency, and water usage. With color-changing resin you'll see when the first chamber turns; rotate the polishing chamber forward and reload the empty one.

Does this qualify for free shipping?
No — due to size and weight this item is excluded from our free shipping program. Standard shipping rates apply at checkout. If you're local, in-store pickup at our Lawrenceville GA location is free.

Will it work with my existing RO/DI system?
Most likely yes — IceCap canisters use standard fittings. Check your system's tubing size (typically 1/4" or 3/8") and make sure your inputs/outputs match.