Faulty check valve? - The Planted Tank Forum
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post #1 of 8 (permalink) Old 05-22-2020, 02:29 PM Thread Starter
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I just plumbed CO2 to a second tank a couple days ago and installed a check valve between the in-tank ceramic diffuser and the needle valve. I noticed liquid inside the line between the diffuser and check valve AND a few inches beyond the check valve. Not sure how this could be. Shouldn't the check valve close when there is no CO2 pressure/flowing through it? I got the check valve from Mcmaster and it wasn't cheap. According to the spec sheet, the valve has a minimum opening pressure of 1 psi. This sounds awfully low to me. Regardless, the valve should be closing once the CO2 valve closes and water should not be flowing backwards.

https://www.mcmaster.com/1056T2

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post #2 of 8 (permalink) Old 05-22-2020, 04:07 PM
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Clean it, might need to get it open and make sure the valve seat area is free of debris.


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post #3 of 8 (permalink) Old 05-23-2020, 01:34 AM Thread Starter
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I'll be returning the check valve and already ordered a different one. I got another Swagelok SS-4C-10, which has an opening pressure of 10 psi. This is the same one I used on my other planted tank and it has worked fine. Should have just got another one to begin with.

I'll try that. If I can fix it, I'll sell it. With a 1 psi opening force, even a tiny piece of debris is probably enough to keep the valve open.

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Last edited by Darkblade48; 05-24-2020 at 03:45 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #4 of 8 (permalink) Old 05-23-2020, 05:06 AM
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actually, the lower cracking pressure the better, ...


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post #5 of 8 (permalink) Old 05-23-2020, 11:50 AM
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Wouldn’t a higher cracking pressure valve have a stronger spring therefore close off better?
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post #6 of 8 (permalink) Old 05-23-2020, 02:13 PM
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Quote:
Originally Posted by Bettatail View Post
actually, the lower cracking pressure the better, ...

As I understand cracking pressure, this would not seem to be true. I have often read this but disagree.
If cracking pressure is how much pressure from thank is required to "crack" the valve open, it seems better for us to use higher cracking pressure to get the valve open, as that also means it closes more firmly when the gas is off?
I think of it as a door, if we had a door which takes one man to open it is harder for anything coming back through if it takes two men to open the same door!
I have never seen an explanation of why low cracking pressure is better, other than it may make leaks in the tubing if way too strong.
Perhaps others have a different definition of cracking pressure?
But it is also very common for check valves to leak. One problem that I find is due to the extreme hard water I have. Once it reaches a check valve and dries there, the mineral deposits often will cause the check valve to ooze a bit in the future.
I have access to ordering from either Ark-Plas or US Plastics and find their check valves in the 5-10 PSI range are what I like.
https://www.ark-plas.com/category.php?c=105
Most any type of these will do for something as simple/safe, non corrosive as CO2 at our low pressures and short distance.
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post #7 of 8 (permalink) Old 05-23-2020, 04:05 PM
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don't get me wrong, I mean low cracking pressure better for the whole system, and it is not the normal plastic check valve we are talking about here, we are comparing $30+ industrial grade check valves, especially the Parker or swagelok one to a generic check valve.

Debris stuck at the valve seat is not much difference if check valve has a 1/3 or 10 psi cracking pressure, and I think OP aimed at the the wrong issue, it is not the lower cracking pressure of the check valve that welcome trouble, but the build quality of a generic check valve compares to the swagelok or parker.

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Originally Posted by PlantedRich View Post
I have never seen an explanation of why low cracking pressure is better, other than it may make leaks in the tubing if way too strong.
.
It is easy to explain, you can see the bubble counters with build in check valve(low quality), if the springs in those check valve are too strong, the gas flow through bubble counter is sudden rush of bubbles in intervals.
Same as high quality check valve with high cracking pressure, we don't want this sudden rush(fluctuations of pressure), we want linear flow of co2, so lower the cracking pressure, more smooth the flow rate.

Swagelok 1/3 psi is the best, up to 5 psi, normally more than 5 psi you will notice some weird behavior of gas flow on your co2 system, ...


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Last edited by Darkblade48; 05-24-2020 at 03:46 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #8 of 8 (permalink) Old 05-23-2020, 10:43 PM
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Yes I will fully agree that many of the cheap setups are not going to give good steady performance, no matter what check valve is used.
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