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Old 10-03-2020, 10:33 PM   #1 (permalink)
Hank Junior
Join Date: Oct 2020
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Default CO2 Diffuser

Got a problem with a CO2 diffuser I bought, won't mention the brand but its Chinese and was not cheap, made of glass. Every 2-3 days it fills completely with water (begins filling when the CO2 is off at night) which stops it working. I haven't had an aquarium for 20 years but I don't remember my last diffuser having this problem.

As I don't have a non-return valve in the CO2 line (I should have fitted one) I not only have to remove it and suck the water out every 2 days, but also the line which as it is connected to a tank does not empty of water easily. The bubble counter above the solenoid has a non-return valve, so the solenoid is safe, but that is not the problem.

Its pretty annoying. Currently have removed the diffuser and have the large gas bubbles pooling below a shelf in the tank, so at least the gas sits in the tank water without escaping. Its not ideal.

Should a diffuser fill with water? With the supply off there seems to be a pressure drop which allows water in. Not clear to me why there is a pressure drop? I have soapy water tested my entire CO2 supply (that was a real pain but a necessary one) so I know there are no leaks. Does gas leak through the tubing slowly overnight? I am using common air tube.

Maybe the pressure escapes via the gas-water interface at the diffuser, causing a pressure drop (as gas pressure goes to atmospheric), but how would that let water in - how can the gas be replaced by water? Doesn't make sense to me. If water is flowing into the gas line surely the gas must be leaving somehow?

Thanks for any ideas. I am thinking of buying another diffuser and fitting a non-return valve in the line next to the diffuser to ensure my gas line does not back fill with water.
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