Back-pressure Bubble Counter Issue - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 08-20-2018, 01:02 PM Thread Starter
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Question Back-pressure Bubble Counter Issue

I just installed a DIY Griggs reactor on my Fluval 406 filter. It's 25" long with 2" PVC pipe. The CO2 is fed from an aquateck regulator with a brass check valve right after the needle valve and the glass bubble counter just before the reactor. See pics here: https://photos.app.goo.gl/9ECQ8YVtQRQ4b4bd9

I'm currently getting a very unsteady bubble stream and I can see the water in the bubble counter bounce forward and backward as it trys to overcome the back-pressure of the reactor. This wasn't an issue on my system when running a diffuser...
Is this a issue of:
1) Faulty check valve - solution, buy a new one
2) to much co2/air in the line before the check valve, allowing co2 compression - solution, move it just before the bubble counter
3) too low working pressure on the reg (it's currently at 50 psi) - solution, up working pressure
4) wrong placement of check valve - solution, place check valve right after bubble counter, before reactor
5) Other?

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Last edited by Vinster8108; 08-20-2018 at 01:02 PM. Reason: spelling
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post #2 of 6 (permalink) Old 08-20-2018, 01:37 PM
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I am a firm believer in the Grigg's design and find it works very well. But then I must also point out that you do not have a Grigg's reactor as about the only part that relates is using PVC!
But still that doesn't sound like the problem and what you have may well work fine with some small changes.
There will only be a small PSI from the reactor, due mostly to the height difference between that point and the tank water level. Maybe only a few feet with the filter adding a tiny amount. So I run my reactors at ten PSI to avoid any potential extra stress on the tubing and fittings. No need of fifty!
If it is really not working at a low PSI, check the way the check valve is placed as well as question the check valve "cracking pressure" which is the level at which it begins to allow flow. I find low cracking pressure valves fail too soon for me but those rated at 10-15 PSI are better for me. It may be worthwhile to remove the check valve to do a test of how flow works without but I would not do that first.
When in doubt while troubleshooting, I often do the easy things first and rearranging tubing is not always the easy one.
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post #3 of 6 (permalink) Old 08-20-2018, 06:10 PM Thread Starter
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Gotcha, it will try lowing the PSI and double check the check valve. Why do you say this is not the Rex Griggs style CO2 reactor, could you elaborate on what is? Thanks

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post #4 of 6 (permalink) Old 08-20-2018, 06:35 PM
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This is the one that I follow as being the closest to the original and at first look it may seem the same but there are some differences that may make a big difference in the use.
How To Build A CO2 Reactor | Build a Regulator | Test Kit

It is smaller and and shorter but the way the tubing enters and leaves can change that a bit. But the real difference is how and where the CO2 enters. When it enters away from the top, the distance to travel before it is released into the tank is shorter and when it enters through a fitting at the side, it may wind up in a "dead zone" along the side so that it flows up to collect at the top. If a large bubble forms there, we can get splashing noise.
The design of your reactor is one that is often used due to a lack of confidence that pulling the tubing through an undersized hole will actually work but I do not like to stray from a design that is so universally accepted. Kind of the thought that if a system works so well that so many of us are using it, do I really want to change it?
But that is not saying the design will not work, just seems to be daring the gremlins to come out!
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post #5 of 6 (permalink) Old 08-21-2018, 06:16 PM Thread Starter
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I think the majority of the diffusion will happen at the top of the reactor in the turbulent zone, along with the small bubbles that then are formed and get caught suspended in the flow. Anyhow seems to be working alright, pH has dropped to 7.4 to 6.4.

Two faults were happening:
1) the check valve was too far from the bubble counter. Placing it right before has stopped almost all of the inconsistency. I believe the CO2 in the line between the bubble counter and check valve was able to be compressed, causing the fluctuations.
2) My aquatek regulator is crap lol. Turns out my working pressure is "zero" at 20 psi. So I'm running it at 20 psi now (40 on the gauge). In addition, the working pressure dose not hold steady... happens on both my aquatek regulators. Fluctuates about 10 psi every few seconds.

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post #6 of 6 (permalink) Old 08-24-2018, 01:38 AM
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If there is a long run of tubing, it may be something I call "ballooning" as much as the CO2 compression. We can't see it but the thin walls of some tubing will expand a bit and that can give a low flow at the end while it is expanding and then once it reaches the full extent that it will swell the flow begins to move on through and makes us think the needle valve, reg or some other part is funky to mess with our mind!
But since I can't see the expansion, just seems to work when I get into the higher pressure on thin tubing, I really can't say I could prove this idea. At one point I wanted to run a second tank in another room off a single reg and that meant a long run of tubing. It was just too weird and I gave up on that one!!
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bubble counter, check valve, co2 reactor, fluval 406, rex grigg

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