CO2 degasser for RODI units

I recently did a fun DIY project and wanted to share in case it inspires others. Marc Levenson mentioned a friend showed him a DIY degassing chamber during one of his live streams. His friend explained his home uses a well which can have excess CO2 in the water. CO2 will expire the resin we use in our RODI units. I’m on a well, make a lot of RODI, and noticed I was also going through resin rather quickly.

You can test for excess CO2 by taking a water sample and measuring the PH. Next you leave the water sample alone for 24-48 hours to “gas off” and measure the PH again. If the PH goes up you likely had CO2 in the water that gassed off. (Note - in my case I did this test three times but only saw the PH go up once.) Despite my inconclusive results I decide to give it a try.

You have a few options to solve this problem. You can use CO2 absorbing media (expensive), you can let the water “gas off” in an open container for 24-48 hours before running it through your resin (free but adds a step and container), or you can try to build an inline degasser. I found several other reefers who had attempted to create DIY degassing chambers like the one below.

I wanted my degasser to run inline with the source water and not have to worry about overflows (issue with the above design). This design is very simple but does require a booster pump. It was three easy steps:

  1. I added a float value to a 5 gallon bucket and ran my source water into the bucket.

  2. I added a powerful air pump and air stones into the 5 gallon bucket to help gas off excess CO2.

  3. I ran an RODI from the bucket into my booster pump.

The air pump is loud when it runs but provides a lot of air. Here is what the degasser looks like when it is running:


Finished product with the lid installed to avoid contamination:

I make a lot of RODI water and was spending in excess of $250 of resin a year. This has saved 4-5x the amount of resin I was using so it quickly paid for itself. If you try to make a degasser be sure the share!

Supply list:

  1. Air pump: https://www.amazon.com/gp/product/B07RRV3XKX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

  2. Air stones: https://www.amazon.com/gp/product/B01LYLNQWV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

  3. Float valve:
    https://www.amazon.com/gp/product/B01N0IOJ5D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Nice write up! That thread on R2R just won’t die! :slight_smile: I still get people asking about it. One of these days I’m going to spend some time making something that sits in a DI canister that does this without a fuss. It might not be any time soon though lol

I wound up going a similar way that you did and I run my RO into a 5g bucket where I aerate it for 24 hours before running it through the DI stage. I found I don’t tend to need water on demand too often so having 5g in the DI bucket and another 5g in the RO, ready to finalize, works for me.