Ultra High Purity DI Resin Cartridge

Water spots on a freshly washed car. Algae in a reef tank that keeps coming back. Lab results thrown off by trace minerals. Each comes down to the same thing: dissolved solids that ordinary filters, and even reverse osmosis, leave behind in small amounts. When the job needs water with almost nothing dissolved in it, the answer is deionization.

The Crystal Quest Ultra High Purity DI Resin Cartridge is a mixed bed deionization (DI) cartridge. It is filled with a blend of two ion exchange resins that together remove dissolved ionic contaminants and drive total dissolved solids (TDS) toward zero. It is built as the final polishing stage after reverse osmosis, for reef-keeping, laboratory water, rinsing and plating, and spot-free washing.

Not intended for drinking use. This cartridge makes technical water for the uses above. See why below.

At a glance

• Mixed bed DI resin that removes both positive and negative dissolved ions in one pass
• Ultra pure output: rated 14 to 18 megohm-cm resistivity for the published slim sizes
• Made for polishing RO water, where it lasts many times longer than on tap water
• Capacity stated in grains, with gallons published at two feed water levels
• Four sizes for standard 2.5" and Big Blue housings

What you are looking at

Inside the cartridge is a bed of resin beads in two colors: dark beads of cation resin and light amber beads of anion resin, mixed together. A pad holds the bed in place and the cartridge seals into a standard housing. The two resins arrive fully charged, the cation resin in the hydrogen form and the anion resin in the hydroxide form, ready to trade those ions for whatever is dissolved in your water.

How a DI resin cartridge works

Two resins, one result: water

Dissolved solids are ions. Calcium, magnesium and sodium carry a positive charge; chloride, sulfate, nitrate and bicarbonate carry a negative charge. The strong acid cation resin captures every positive ion and releases a hydrogen ion in its place. The strong base anion resin captures every negative ion and releases a hydroxide ion. Hydrogen and hydroxide combine into pure water, so what leaves the cartridge is water with almost nothing dissolved in it.

Why a mixed bed polishes so well

In a mixed bed, the cation and anion beads sit side by side. Water passes through many alternating exchange steps on its way through the cartridge, so ions that slip past one bead are caught by the next. That is how a mixed bed reaches purity that separate resin stages cannot.

Measuring purity: resistivity

The fewer ions water carries, the worse it conducts electricity. DI water is graded by resistivity, in megohm-cm: the higher the number, the purer the water. A TDS meter reads close to zero on DI water, which is why high-purity users measure resistivity instead.

Why it belongs after RO

DI capacity is measured in grains of dissolved solids, and every grain removed uses part of the resin. Feed it tap water and it spends its capacity on minerals that an RO membrane removes far more economically. Feed it RO water and the same resin lasts many times longer. Dissolved carbon dioxide also uses anion capacity, and chlorine damages resin, so the carbon and RO stages ahead of DI protect it.

What it reduces

Primary target: dissolved ionic contaminants and total dissolved solids (TDS) that RO leaves behind in small amounts, including:

• Hardness minerals: calcium and magnesium
• Sodium and other dissolved metal ions
• Chloride, sulfate, nitrate and bicarbonate (alkalinity)

Not designed to treat: bacteria and viruses, sediment, chlorine and most dissolved organic chemicals, which carry no charge. Those belong to the sediment, carbon and RO stages ahead of the DI cartridge.

Why it is not intended for drinking use

• The minerals are gone. Tap water can contribute calcium and magnesium to your daily intake. DI water contributes almost none.
• It is "hungry" water. With nearly every ion removed and no buffering left, deionized water is easily contaminated and can corrode many of the materials it touches, and its pH drifts lower once it meets air.
• It does not make water safe. DI resin does not remove bacteria or particles and does little for most organic chemicals.
• It is a technical water product. Deionized water is used in laboratory and medical water systems. This cartridge is built for reef, lab, rinsing, plating and spot-free uses, and Crystal Quest makes no drinking water treatment claim for it. For low-TDS drinking water, choose a Crystal Quest reverse osmosis system.

Who uses it

• Reef and aquarium keepers who want top-off and mixing water without the silicates, nitrate and phosphate that feed algae.
• Laboratories preparing water for testing, rinsing and reagents.
• Medical water systems that need deionized water.
• Rinsing and plating operations where dissolved solids leave residue or spoil a finish.
• Spot-free washing of vehicles, windows and solar panels.
• Electronics, optical and pharmaceutical production that needs very low TDS water.

Why Crystal Quest

• Real mixed bed resin, hydrogen and hydroxide form, ready to polish from the first gallon.
• Published performance: resistivity, grain capacity, gallons at two feed levels and flow for the slim sizes, in the Specifications tab.
• Ultrapure systems experience: Crystal Quest builds RO and DI systems for homes, labs and commercial users.
• Over 1,000,000 people served since 1994. Crystal Quest builds under ISO 9001 quality management, has made water filtration in the USA for over 30 years and offers lifetime support by phone, email or chat.

Where it fits

• After an RO system, as the final polishing stage before the point of use.
• Countertop and under-sink DI housings that take the 2-7/8" x 9-3/4" or 2-7/8" x 20" size.
• Big Blue housings for higher-volume polishing with the 4-5/8" sizes.

Choose the size printed on your current cartridge or in your order history: 2-7/8" x 9-3/4" (CQE-RC-0500), 2-7/8" x 20" (CQE-RC-0501), 4-5/8" x 9-3/4" (CQE-RC-0502) or 4-5/8" x 20" (CQE-RC-0503).

Common questions

DI resin cartridge specifications

Published ratings apply to the selected cartridge and listed conditions. Capacity and output depend on feed water TDS, flow and usage. Contact Crystal Quest with the part number to confirm the flow and service plan for the 4-5/8" sizes.

Media and treatment

Operating conditions and materials (2-7/8" sizes)

*Capacity and gallons are estimates. Actual life depends on feed water TDS, flow and usage.