CO2 - Backflow troubleshooting

[stowcenter93]

I'm farting around with a CO2 system in my 29 gallon. It's not necessary, but I'm out of space in my apartment for new tanks and wanted to try and experiment with it.

When the solonoid goes off and the line depressurizes, I get backflow to the check valve, which is located just on the outside of the tank rim. The Canister is on the floor. 

I was having no issues for a bit but I noticed that I was no longer getting bubbles and realized I still had water in the diffuser (and up into the tubing I suppose) that was not forced out.

When I increased the bubble rate, I watched the water be forced down though and up out the diffuser. My first thought was a clog, but is there something else I'm missing?

[Seattle_Aquarist]

Hi @stowcenter93

Check valves that remain reliable for long periods of time are very difficult to find.  I've tried several types both plastic and brass.  Probably the ones that have lasted the longest are Clippard MCV-1BB brass check valves with the appropriate barbed ends.  However, because the check valves are subject to both contact with water and CO2 gas the resulting carbonic acid that results will eventually cause it to fail.  That is the same problem with with most check valves that use a metal spring or any metal in them.  

I recently picked up some plastic teflon check valves from Mettleair which I have not yet tried.  Teflon is very resistant to carbonic acid.  The CVU-2-KV are not expensive (less than $3) and based upon my test with a rare earth magnet does not seem to contain any metal.  The next time one of my brass valve fail I will be trying one.  -Roy

Edited June 15, 2022 by Seattle_Aquarist