When to Change Out Your RO/DI Filters

What to Know About RO/DI Filter Replacements

Maintaining your RO/DI system is an essential part of protecting your reef tank from contaminants that could potentially harm your aquatic life.

Your system serves as the front-line defense against impurities in your water supply, and it's essential to change the filters on time to prevent these harmful substances from sneaking through and causing issues in your aquarium.

Monitoring the performance of each stage of your RO/DI system is the best way to maximize the lifespan of your filters and ensure you’re replacing them before they can compromise your tank. Since everyone’s source water quality varies, there is no universal timeframe for filter replacement.

This is why it’s important to monitor performance closely. Fortunately, tracking the condition of your RO/DI filters is relatively simple with the right tools and a little bit of knowledge.

Why Choose Air, Water & Ice for Your RO/DI Needs?

At Air, Water & Ice, we are experts in RO/DI systems with extensive professional knowledge on when and how to replace your filters. Whether you're a seasoned saltwater aquarium enthusiast or new to the hobby, we provide the guidance and products you need to keep your tank's water pristine.

Our selection of high-quality filters and monitoring tools, combined with our expert advice, ensures that your RO/DI system is always operating at peak efficiency.

Required Supplies

• Inline Pressure Gauge
• TDS Meter
• Total Chlorine Test Strips
• Replacement RO/DI Filter Cartridges

When to Change Your Sediment Filters

The sediment filter is your first line of defense, capturing large particles and debris before they reach the more sensitive components of your RO/DI system. You'll know it's time to replace the sediment filter when you notice a pressure drop going into your RO membrane, as indicated by the inline pressure gauge.

As the sediment filter becomes clogged, you will observe a pressure drop on your inline pressure gauge, installed between your carbon block filter and the RO membrane. Additionally, the filter will change color or darken over time as it becomes blocked with debris.

If your RO system doesn't have a pressure gauge, it's highly recommended to install one. Air, Water & Ice offers complete Pressure Gauge Install Kits and replacement gauges, along with a detailed instructional video to guide you through the installation process.

Typical Replacement Interval

While the exact timing varies based on your source water quality, a general rule of thumb is to replace sediment filters every 6-12 months. At Air, Water & Ice, we recommend our 10 micron depth sediment filter, known for their truly progressive filtration fibers that last longer and outperform most other sediment filters in their price range. Smaller micron sized sediment filters may be used (and there are reasons why you would want a lower micron size sediment filter); however, smaller micron sized sediment filters cause a reduction in line pressure… this drop in pressure will increasingly decrease the purity of your pure water as your membrane (does almost all the work) loves higher pressure. Never install less than a one micron sediment filter… it will end up suffocating your membrane if you do not have a booster pump installed on your system.  

When to Change Your Carbon Block Filters

Carbon block filters are often the second and often third stage of filtration in your RO/DI system, crucial for removing chlorine and chloramines. To determine if your carbon filter needs replacing, test for the presence of chlorine and chloramines using Total Chlorine Test Strips or using a flow meter to gauge how many gallons of water the carbon blocks have prefiltered.  

To test for total chlorine, run your RO system for 15 minutes, then collect a sample of wastewater from the system. Submerge the test strip in the sample for 2 minutes, and wait an additional 10 minutes for the color to develop. If the test indicates more than 0.5 PPM of total chlorine, it's time to swap out your carbon block filters.

Typical Replacement Interval

Carbon block filters generally need to be replaced at least every 12 months. As with sediment filters, a drop in input pressure can also signal a clogged carbon filter.

When to Change Your RO Membrane

The RO membrane is the heart of your system, responsible for removing the majority of contaminants. To monitor its performance, use an inline or handheld TDS meter to measure the rejection rate of your membrane. As the TDS level in the product water starts to rise, it indicates that the membrane is becoming less effective and needs to be replaced.

To calculate the rejection rate, measure the TDS of your tap water and the TDS of the water coming out of your RO membrane before it passes through the DI resin. A well-functioning membrane typically has a rejection rate of 96%-99%. If this rate drops below 96%, it’s time to replace the membrane.

Typical Replacement Interval

RO membranes can last for 2+ years with proper maintenance, including regular pre-filter changes and the use of a flush valve. Air, Water & Ice offers a range of high-quality membranes designed to provide maximum filtration efficiency.

When to Change Your DI Resin

The DI resin is the final stage of filtration, responsible for absorbing any remaining contaminants. The best way to monitor the performance of your DI resin is to use an inline TDS meter. If the TDS reading of your DI water is anything other than 0 PPM, it's time to replace the DI resin.

Using color-changing DI resin is a practical approach to knowing when to change it out. When 75% of the resin has changed color, it's time to replace it. Do not wait until 100% of the resin is exhausted, as this can lead to contaminants slipping through.

Typical Replacement Interval

The replacement schedule for DI resin depends on your specific water quality and usage. Air, Water & Ice offers a variety of DI resins, including Mixed Bed DI Resin and Single Bed Pro Series DI Resins, tailored to different filtration needs.

Trust Air, Water & Ice for Expert RO/DI System Maintenance!

Invest in quality purified water with Air, Water & Ice! Founded in 1982, Air, Water & Ice is your go-to source for professional-grade RODI systems, filters, and maintenance supplies. Our extensive knowledge and quality products ensure that your system remains in top condition, providing your reef tank with the purest water possible. Whether you're replacing filters or need advice on system maintenance, our team is here to help.

At Air, Water & Ice, we are the experts when it comes to RODI systems, deionization products, RO systems, filters, membranes, water testing products, pumps, parts/fittings, and more. If you have questions, please contact us sales@airwaterice.com at or by phone at (772) 461-0256.

Read More: How to Pick the Best RODI System