# Back flow in co2 tubing, even with non return valve



## parotet (6 Jun 2015)

Hi all

Since I'm using an in-tank ceramic diffuser I have noticed that I have some back flow in the co2 tubing. I got the ceramic diffuser, then a bubble counter and then a non return valve. I even bought the JBL one that is ugly but they told me it is very good (nuts and good quality). My guess is that each time the timer turns off the co2 there are some microdrops of water that are able to pass through the valve, and when this happens during several weeks there is some water in the tubing between the valve and the solenoid. It's been like this for 3 months now without any problem (today it's been the first time I have drained it). Does it happen to you? Is it normal? Any way to prevent this from happening... Maybe another check valve?
It also happened to me using a built-in check valve on a bubble counter...

Jordi


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## Julian (6 Jun 2015)

Not sure what the answer is, but keep in mind that if you add check valves to CO2 pipe, it requires more pressure to get the CO2 into the diffuser. This can result in the pipe (for want of a better word) 'bursting' off the check valve.


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## parotet (6 Jun 2015)

Back from my LFS and they told me that the more length you have between the diffuser and the check valve, the more pressure the check valve will have to deal with. In some tanks they have the check valve between the ceramic diffuser and the bubble counter. I'm wondering what would happen if I put one before and one after. I think I have enough working pressure to run it (I can use inline diffuser that I think need quite a good amount of pressure). I will let you know...

Jordi


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## Andy Thurston (6 Jun 2015)

I had this problem when I first started with co2. any backflow of water into the pipe is caused by cheapy crappy check valves and a leak in the system somewhere. when my co2 turns off, if theres a bubble in the bubble counter it will still be there in the morning just before the co2 comes back on 
http://www.co2art.co.uk/collections/check-valves/products/hight-quality-co2-check-valve-non-return
these are the only check valves aimed at planted tanks that will work long term but they do have quite a high cracking pressure. I wont use any other check valve now


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## Julian (6 Jun 2015)

Big clown said:


> I had this problem when I first started with co2. any backflow of water into the pipe is caused by cheapy crappy check valves and a leak in the system somewhere. when my co2 turns off, if theres a bubble in the bubble counter it will still be there in the morning just before the co2 comes back on
> http://www.co2art.co.uk/collections/check-valves/products/hight-quality-co2-check-valve-non-return
> these are the only check valves aimed at planted tanks that will work long term but they do have quite a high cracking pressure. I wont use any other check valve now



I _had _the same one. Be careful when you tighten it, the plastic bolt thingys are a little flimsy.


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## JohnC (7 Jun 2015)

I made the mistake a few years ago of bulk buying check values from ebay. now i'm sold on quality versions. save so much hassle in the long run.


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## parotet (7 Jun 2015)

I use this one: https://www.jbl.de/en/aquatics-freshwater-products/detail/3634/jbl-proflora-safestop and today I have added a second cheap one between the diffuser and the bubble counter. No problem for the moment, the pressurized co2 can work with two of them. let's see if I can completely avoid the back flow. Of course I will try to leave only one, but today I was too lazy.

Jordi


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## ian_m (8 Jun 2015)

Problem with cheap one way valves, aimed for airlines, is the CO2 will attack the rubber inside them (been there done that). Either rubber going hard and crumbling (one way'ness stops) or rubber "melts" (and flow stops). You must really use one that states it is for CO2.


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## parotet (8 Jun 2015)

Mine (the JBL one) is for CO2... as mentioned yesterday, I have added a standard check valve between the diffuser and the bubble counter. The system worked ok with two valves and no back flow at all when the system stopped. Not sure if I will leave both or one.
By the way, does it make sense what they told me at the LFS? (the more length you have between the diffuser and the check valve, the more pressure the check valve will have to deal with). It is quite strange to me. This happens in my 20ish liters tank and I have seen plenty of very large tanks in which the tubing is much longer and can work with a standard plastic check valve.

Jordi


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## Andrew Butler (12 Jan 2018)

Old thread I know but has anyone found a pushfit version?


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