Check Valve Cracking Pressure (1 psi vs 1/3 psi) - The Planted Tank Forum
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post #1 of 12 (permalink) Old 05-31-2017, 02:04 AM Thread Starter
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Check Valve Cracking Pressure (1 psi vs 1/3 psi)

Hey all,

So I can't seem to find an answer to this but when we're talking check valves on co2 regulators, it seems that 1/3 psi cracking pressure is preferable but that 1 psi will work as well. Why is 1/3 psi preferable though? Can the 1 psi cracking pressure potentially cause problems?

Thanks in advance!
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post #2 of 12 (permalink) Old 05-31-2017, 02:54 AM
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There seems to be some differing opinions of which is best. Some say the least pressure is best but then there is the other side which asks if you are using ten+ PSI coming from the reg, why not just go with a check valve that closes more firmly?
I have not had issues with either, so tend to ignore the question but if I were asked, I might come down on the one which closes more firmly as it would seem less prone to letting a slight amount of water leak back past it?
I occasionally run into this when using check valves in water lines. A swing check is just a simple gate that swings shut on gravity to seal. They tend to let water leak back so I use a solenoid when I really want a seal.
Entirely different application but I see no reason a 5-10 PSI will go open the check valve rated 1/3 or 1 PSI. If we were speaking of diy co2, yes, I would want the easy open one.
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post #3 of 12 (permalink) Old 05-31-2017, 03:13 AM
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My thought process goes the other way from @PlantedRich. The CO2 can take a long time to build up pressure at the volumes we use, so it may take some time to build up the full 5-10 lbs. Then, when the valve cracks open, the pressure drops, closing it again. In my experience, you can end up with an erratic bubble count with a check valve that is too stiff. If you're talking about the check valve built into a bubble counter, like the ones that screw right into the needle valve, this might not be as big of an issue. For me, I run two check valves; one right after the needle valve, and one right before the reactor. The distance between the reactor and the bubble counter would take forever to build up to enough pressure, then dump rapidly when the valve cracked open.

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post #4 of 12 (permalink) Old 05-31-2017, 11:35 AM Thread Starter
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Nice info here, thank you!

@jellopuddinpop the reason I ask is because I'm looking for a check valve to go right between my needle valve and a JBJ-style bubble counter (whose built-in check valve will surely fail in time). Erratic bubble count is not a big a deal to me as letting water back past the check valve and into the needle valve. I will be running an additional kynar check valve between the bubble counter and my inline atomizer so I'm not worried about water from the tank itself, just the bubble counter. So it shouldn't really matter too much?

@PlantedRich so just to confirm, the 1 psi check valve closes more firmly than the 1/3 psi check valve? And you would lean towards the 1 psi cracking pressure valve? I run an inline atomizer so my output pressure is 35 psi + if that matters.

Thanks again!
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post #5 of 12 (permalink) Old 05-31-2017, 11:53 AM
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Quote:
Originally Posted by ItsDubC View Post
Nice info here, thank you!

@jellopuddinpop the reason I ask is because I'm looking for a check valve to go right between my needle valve and a JBJ-style bubble counter (whose built-in check valve will surely fail in time). Erratic bubble count is not a big a deal to me as letting water back past the check valve and into the needle valve. I will be running an additional kynar check valve between the bubble counter and my inline atomizer so I'm not worried about water from the tank itself, just the bubble counter. So it shouldn't really matter too much?

@PlantedRich so just to confirm, the 1 psi check valve closes more firmly than the 1/3 psi check valve? And you would lean towards the 1 psi cracking pressure valve? I run an inline atomizer so my output pressure is 35 psi + if that matters.

Thanks again!
I agree that my concern shouldn't matter at all with the one between the needle valve and the bubble counter. I would consider one with a low cracking pressure for the one near the diffuser.

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post #6 of 12 (permalink) Old 05-31-2017, 02:15 PM
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Good time to discuss when we don't see things the same. I might need to change my mind? Happens ever now and then!
Assume we are lining things up in this order? Reg, solenoid, needle valve and then however many check valves we use. I do add my bubble counter out inline away fro the other parts but it offers little resistance and should not impede flow.
But what I see is this. The 1/3 PSI does take less pressure to open. But it doesn't snap open and then snap closed as it is a spring that is resisting the pressure. What I think will happen is that as the solenoid opens, the pressure we set is going to be there pretty quick if the check valve closes at whatever pressure it is designed. Will it let more gas through after it reaches the lower limit of the pressure it is designed to open or does the spring push the valve shut as the pressure reduces?
Possibly we are speaking of different types of check valves? One that a spring pushes it closed as I'm thinking but perhaps the one you use has some type of snap opening that once open, stays open even when the pressure goes below the opening limit?
The one I'm familiar with will let gas pass as long as long as the pressure is more than the lower limit but then gradually the spring will push it closed as the pressure drops.
That leads me to believe, there will be 3 PSI on the delivery side of a 3PSI valve and 1PSI on that side of a 1PSI. I don't see it as a snap opening but a simple piece that lifts off the seat when pressure is there but settles back down on the seat as pressure reduces. I see it more as a piece of "rubber" that is pressing on the seat at 1PSI or #PSI so the higher pressure presses the opening closed harder to leak less? But they both begin to leak when a bit of grit gets on that seal!
Something like a garden hose with a nozzle. When closed the pressure will be on one side until we open the nozzle but with no delay to build up.
Perhaps wrong and ready to hear other points of view. Just not anything I've ever needed to do much thinking about as I see no problems either way. I just shop for a check valve that seems to last and I fully admit that is a bit of a trick as they seem to fail sooner than later.

Is it possible the idea of lower being better came from airline use where a diaphragm pump needs really low resistance as they are so weak?
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post #7 of 12 (permalink) Old 05-31-2017, 04:44 PM Thread Starter
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I know many ppl have used Swagelok check valves on their regulators and these are described as "poppet" check valves on Swagelok's site. Unfortunately, the Wikipedia article about poppet valves states that there are some that use springs and others that do not, so I don't exactly know how the Swagelok check valves are configured. The 2d and 3d drawings of the valves on the Swagelok site don't give any details about the interior of the valves themselves.

I'm starting to think it's just safer to run a bubble counter inline along the co2 tubing rather than right after the needle valve. It's so convenient there tho
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post #8 of 12 (permalink) Old 05-31-2017, 06:15 PM
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[QUOTE=ItsDubC;

I'm starting to think it's just safer to run a bubble counter inline along the co2 tubing rather than right after the needle valve. It's so convenient there tho [/QUOTE]

I'm not up on what "poppet" would mean in this case. I might do some more checking on that point. Maybe part of the discussion needs to be "which" check valve as much as what pressure?
But for the location of the bubble counter, I do like running things off away from the reg as much as possible. I just find it more convenient for the way I operate. All my regs are hidden so that appearance is not a big deal so I spread it out and hang things on the wooden stand. When I think of regs, the reg itself is reasonably heavy but I do want the solenoid close on it so I hard plumb them together but from there on, I am using low pressure and tubing is fine for my use. I find it awkward to take the reg and all the other parts off the CO2 tank each refill so it feels easy to break something when they are all there at the top. I like having the reg/solenoid on the tank so that I can unscrew them and have enough tubing to lay them back out of the way while I move the heavy 20 pound tank out and in. With this, I screw the needle valve to the stand and let the inline Fluval bubble counter hang loose. I usually tuck it under the strap that holds the tank to avoid tipping. I do lots of plumbing but hate the small funky little stuff that costs an arm for a 1/2" elbow, so tubing is by far better for me once I found where to buy the 10-32 fittings.
One setup that I like for my 125 so that I can do it all standing up.

And a different way to arrange the needle valves and counters when I was running two off the same tank/reg. Tank is under the stand but the controls are on top where they are easy to work. I follow very few rules on setting things but just built it to fit each situation. I forget, Is that called " adapt as needed" or is it called "fly by the seat of the pants"?

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post #9 of 12 (permalink) Old 05-31-2017, 07:43 PM
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Quote:
Originally Posted by jellopuddinpop View Post
My thought process goes the other way from @PlantedRich. The CO2 can take a long time to build up pressure at the volumes we use, so it may take some time to build up the full 5-10 lbs. Then, when the valve cracks open, the pressure drops, closing it again. In my experience, you can end up with an erratic bubble count with a check valve that is too stiff. If you're talking about the check valve built into a bubble counter, like the ones that screw right into the needle valve, this might not be as big of an issue. For me, I run two check valves; one right after the needle valve, and one right before the reactor. The distance between the reactor and the bubble counter would take forever to build up to enough pressure, then dump rapidly when the valve cracked open.
I don't understand why it would take any time at all to build up pressure in a regulated system. It should be almost instantaneous.
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post #10 of 12 (permalink) Old 05-31-2017, 07:54 PM
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Quote:
Originally Posted by Kubla View Post
I don't understand why it would take any time at all to build up pressure in a regulated system. It should be almost instantaneous.
The flow of gas is very, very low. Think of how long it would take for pressure to fill up in a garden hose if you're only filling it up with a slow drip.
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post #11 of 12 (permalink) Old 05-31-2017, 10:47 PM Thread Starter
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Interesting setup, @PlantedRich! I never thought about mounting the needle valve to the stand. I agree that having more things connected directly to the regulator adds to the overall cost. But even on many high-end builds like Alan Le's, a lot of them seem to have the bubble counter off the regulator. I assume it's to mitigate risk from the notorious JBJ bubble counters.
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post #12 of 12 (permalink) Old 06-01-2017, 02:14 AM
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I've never run any with the bubble counters right above the stuff I want dry! Just looks scary when I think about how many check valves fail and start letting the water ooze through. while it seems like a needle valve would be pretty tough, the good precise ones we like best are not going to be any better if I let my hard water go in and dry up so that it looks like a tea kettle!
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