6 Reasons Why You May Be Burning Through DI Resin!

“Why am I burning through DI Resin?” is a question that we get asked fairly regularly. As the DI resin is often the most expensive part of maintaining your filters, you will want to make sure that everything is working properly and efficiently. These are the most-common problems and how to fix them.

Chloramines and RO/DI Filters

1. Chloramines - if your DI becomes exhausted after making 30-50 gallons of water, you almost definitely have chloramines. More and more municipalities are adding chloramines to sanitize water. Many on a continual basis, but some will use chloramines sporadically. Chloramines break down into chlorine and ammonia gas. While the RO portion of your system can remove the chlorine portion, the ammonia portion remains. Your DI filter does a great job of removing ammonia: however, it will exhaust very quickly due to the high concentration of ammonia. To remove chloramines, you will need to use two Chloramine Blaster carbon filters in your system. The catalytic carbon used in our Chloramine Blaster cartridges, in conjunction with the longer contact time with using 2 cartridges, will effectively remove chloramines. Most of our RO/DI systems are available with a Chloramine Blaster upgrade. If you already have your system, you can go with our Add-On Chloramine Blaster Kit and upgrade your existing system. Read our Oh No! Chloramines! blog for more information.  

CO2 and RO/DI Filters

2. High CO2 (typically well water) - well water can sometimes have a very high CO2 content. In these scenarios, CO2 will cause the DI resin to become exhausted quickly. The solution is to get rid of the CO2. This can be done by collecting the RO water in a container/reservoir.  Aerate the RO water with a water pump or air pump for 24 to 48 hours to gas off the CO2, then use a water pump to pump water through the DI filter.  

High TDS RO/DI System

3. Water with very high TDS - your DI filter is great at absorbing any TDS leftover from the RO portion of your system; giving you pure, zero-TDS, water. However, how much water your DI can process is proportional to the concentration of TDS. As a general rule, your DI filter can produce approximately 500 gallons of water if water coming out of the RO membrane is at 10ppm. If water coming out of your RO is at 20PPM, the DI will only be able to produce 250 gallons of water. At 50ppm, that number drops to just 100 gallons. For this reason, it is important to keep your RO system running at optimal conditions to ensure the output is as clean as possible. 

DI Filter Water Production Chart

Consider adding a booster pump as it allows you to operate the system at 80PSI, where the RO membrane is most efficient. Flush the RO membrane before and after each use for 30-60 seconds and change out the sediment/carbon-block filters regularly. Running 2 DI filters will help to extend the life of your DI filters as it allows you to fully exhaust each DI filter before changing it out. When a DI cartridge becomes exhausted, the TDS of the water begins to rise. Typically, hobbyists will change out the DI filter when TDS reaches 2-5ppm. At this point, the DI filter still has about 10-15% capacity left. However, there is TDS breakthrough and it is not able to bring your TDS down to zero. Having a second DI filter helps to catch anything missed by the first filter. This allows you to fully use up the capacity of the 1st DI filter without worrying about TDS breakthrough and not catching an exhausted DI filter in time. Once you are ready to change out the DI filter, move the 2nd DI filter to the 1st position and put the new DI filter in the 2nd position. You are still changing just one DI filter at a time, but you can get an extra 10-15% life out of each DI cartridge. Another popular solution of maximizing DI efficiency is to use 3 DI filters: a cation filter, an anion filter and a mix-bed filter. A mix-bed filter has a mix of 60% cation resin and 40% anion resin. You change out the entire cartridge when either of the two resins is exhausted. As TDS is never a perfect 60/40 ratio of positive and negative impurities, you are always wasting some resin. If you use a lot of water or if your TDS is high, this imbalance can add up to a lot of wasted DI resin. By having a separate Cation and Anion filter along with a mix-bed filter that is a catch-all, you are able to swap out only the filter that is fully exhausted. Having separate filters also maximizes the performance of the resin.  

Low Water Pressure & RO/DI Filters

4. Low water pressure - the RO membrane works best at 80PSI. Lower pressure not only causes output to drop, but also increases the TDS of the product water. This higher TDS leads to the DI becoming exhausted quicker. If your water pressure is lower than 45PSI, we recommend adding a booster pump. Not only will water be produced more quickly, it will also have lower TDS. Also, monitor your water pressure. As the sediment filter becomes clogged, the water pressure will drop. Replace the sediment filter whenever you notice the water pressure dropping more than 5PSI. It is a good idea to replace your carbon filter at this time as well.   

High TDS and RO/DI Filters

5. TDS Creep - when your RO/DI system is first turned on, TDS coming out of the RO membrane will be high as there is not enough water pressure for the membrane to work properly. As the pressure builds up, the TDS will start to drop down to normal levels. This is referred to as “TDS Creep” and lasts for about 30 seconds up to 2-3 minutes depending on water conditions. In more-severe cases, this TDS Creep can cause your DI filter to be exhausted much quicker than it otherwise would. The easiest solution is to tee off your water between the RO Membrane and the DI filter and discard the initial batch of water. 

Old DI Resin vs New Deionization Resin

6. Old or Dried-Up DI Resin - DI resin works best when it is fresh. When exposed to CO2 or left for too long, the resin becomes less effective. Only purchase enough DI filters/resin for use in the next 6-12 months. Keep extra DI filters/resin in a cool and dark place. If you are refilling your own DI resin, make sure to reseal the leftover DI resin bag. 

Additional Tips  

One other way to reduce cost is to purchase DI resin and refill your DI cartridges. Refilling your DI cartridge takes just minutes and will save you 30%-50%!  

- When packing your own DI filter, make sure to pack the resin tightly. Loosely packed resin, or pockets inside the resin bed can cause water bypass and unfiltered water to end up in your water reservoir.  

- Replace your sediment & carbon filters regularly as they are inexpensive insurance for RO membrane and DI resin.  

- Lastly, monitor the performance of your RO membrane. A properly-working RO Membrane will have a rejection rate of 95-98% (meaning it removes 95%-98% of the TDS). If you notice that the rejection rate drops significantly below 95%, it is time to replace your RO Membrane. 

By keeping your RO/DI system in tip-top shape, not only will you be providing pure, zero TDS, for your precious fish and corals, you will save money by not wasting water or wasting expensive DI resin. 

At AquaFX, we are committed to providing you with better filters and better service!