DI Pro Expansion (RO System not included)
Important: This product is a DI expansion and polishing unit. It is not a complete reverse osmosis or RO/DI system.
The unit must be installed after the RO membrane and connected to an existing reverse osmosis system. It is designed to provide additional DI-resin capacity and further reduce the remaining dissolved ions in the RO product water.
Tubing Not Included: This expansion unit does not include 1/4-inch OD tubing unless tubing is specifically selected as an optional add-on.
If the optional 5-metre tubing package is longer than required, visit our tubing category to select a more suitable length.
Aquarium and Hydroponics Professional DI Expansion Unit
Increase the deionization capacity of your existing reverse osmosis system with this professional aquarium and hydroponics DI expansion unit.
Designed for reef aquariums, saltwater aquariums, hydroponics, laboratories, dental offices, autoclaves, humidifiers, and other low-mineral water applications, this unit adds two large refillable DI cartridges after the RO membrane.
The larger DI capacity allows the system to treat more RO water before the resin requires replacement. Under suitable operating conditions and with fresh resin, the unit may help produce approximately 0 ppm TDS water.
More Resin Capacity, Less Frequent Maintenance: This expansion unit holds more DI resin than two standard inline DI filters, helping extend operating time between resin changes.
Recommended Applications
- Reef and saltwater aquariums
- Freshwater aquarium water preparation
- Hydroponic and indoor growing systems
- Dental equipment and autoclaves
- Laboratory and testing equipment
- Humidifiers and misting equipment
- Battery-water and specialty low-TDS applications
- Final polishing after an existing RO membrane
How the DI Expansion Unit Works
Reverse osmosis membranes remove most dissolved solids, but a small amount of dissolved ions may remain in the RO product water.
This expansion unit is installed after the RO membrane. The RO water passes through two refillable mixed-bed DI cartridges, where the remaining positively and negatively charged ions are captured by the cation and anion exchange resins.
The first DI cartridge performs most of the final ion removal, while the second cartridge acts as a polishing stage. This two-stage design provides additional protection against TDS breakthrough.
Key Benefits
- Expands the DI capacity of an existing RO system
- Two large refillable DI cartridges provide extended resin life
- May help produce approximately 0 ppm TDS water
- Reduces the frequency of DI-cartridge replacement
- Refillable cartridges lower long-term operating costs
- Clear housings make resin condition easier to inspect
- Suitable for professional aquarium and specialty-water applications
- Can be combined with an optional dual inline TDS meter
Refillable DI Cartridges
This unit uses standard 10-inch refillable cartridges, Part No. 104023. When the DI resin becomes exhausted, the cartridges can be opened, emptied, cleaned, and refilled with fresh mixed-bed ion-exchange resin.
Reusing the cartridge housings helps reduce replacement costs and produces less plastic waste compared with replacing the entire filter cartridge.
DI Resin Maintenance: Keep the DI resin tightly packed inside each refillable cartridge. Loose or settled resin can create open channels that allow water to bypass part of the media and reduce treatment performance.
Replace or refill the resin when the final-water TDS begins to rise above the level required for your application.
Optional Dual Inline TDS Meter
An optional dual inline TDS meter can monitor water quality at two different points in the filtration process.
A recommended monitoring arrangement is:
- First reading: RO water entering the DI expansion unit
- Second reading: Final product water leaving the second DI cartridge
These readings help you evaluate RO-membrane performance and identify when the DI resin is becoming exhausted.
Installation Requirements
- Must be connected after the RO membrane
- Requires an existing reverse osmosis system
- Requires 1/4-inch OD tubing, sold separately unless selected
- Install the cartridges vertically whenever possible
- Confirm the direction of water flow before connection
- Flush new DI resin before using the product water
- Use a TDS meter to monitor inlet and outlet water quality
Important Flushing Instruction: Do not send membrane-preservative water, carbon fines, or initial filter-flush water through the DI expansion unit.
Always flush new pre-filters and the RO membrane before connecting the water flow to the DI cartridges. High-TDS flush water can prematurely exhaust the resin.
Booster-Pump Recommendation
For most RO systems using membranes rated at 100 GPD or higher, a properly sized booster pump may be recommended when the incoming water pressure is too low.
A booster pump helps the RO membrane operate at the correct pressure, which improves membrane rejection and reduces the amount of TDS reaching the DI resin. Lower RO-water TDS generally results in longer DI-resin life.
View the available reverse osmosis booster pumps .
Before Adding a Booster Pump: Confirm your feed-water pressure, RO membrane capacity, pump voltage, and existing shut-off controls to select the correct pump kit.
Included Components
- Professional DI expansion-unit mounting bracket
- Two standard 10-inch refillable DI cartridges
- Two DI filter housings
- Housing caps and connection fittings
- Standard assembly components
Not Included: Reverse osmosis system, RO membrane, pre-filters, booster pump, TDS meter, storage tank, faucet, and 1/4-inch OD tubing are not included unless specifically selected or stated in the product title.
Performance and Resin-Life Notice
DI-resin life cannot be determined by a fixed number of gallons for every installation. The total amount of water produced depends primarily on the TDS entering the DI expansion unit.
- Lower RO-water TDS provides longer DI-resin life
- Higher RO-water TDS exhausts the resin more quickly
- Poor RO-membrane rejection greatly reduces DI-resin life
- Higher water usage requires more frequent resin replacement
- Loose resin packing can reduce filter performance
Performance Notice: Final-water TDS, conductivity, resistivity, resin life, and total water production vary according to RO-water TDS, water pressure, membrane condition, resin quality, resin packing, flow rate, temperature, and overall system configuration.
TDS = Total Dissolved Solids.
