I do not know much at all about DIY co2. But there are some issues with your plan for sure. For starters a needle valve is not intended to be used as an on/off valve. Its just supposed to control flow but not turn it "off". Second, no matter what you do the chemical reaction is going to continue and co2 will continue being produced and build up pressure if it has no way to release which is not a good idea.

 

Sorry, I didn't watch the video, but I run DIY CO2 with baking soda/citric acid using this setup:

https://smile.amazon.com/gp/product/B008CUZJF6/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

I just turn it off at night by turning the needle valve down to stop the CO2 from going into the tank. I have never had an explosion because the reaction is not continuous. However, I've not had one of these last more than 6 months because something always happens to the needle valve which might be caused by my turning it off and on every day.

 

Awesome. If its not continuous then I can turn it off every night and not run an air stone by it. Thanks!

 

Turning the needle valve all the way is one of those things that we often see from folks who don't think all the way through what they are doing. Part of the question and the results will depend on the needle valve and how it is made. A good quality needle valve will be made with really good metal that can be machined and polished to a nice finish. That is where the precision comes in as good metal can be made so that the needle has a long fine taper and fine threads to move that needle the tiny amount we want. A short chunky needle made of cheap pot metal can't be polished and machined well.
So if we have a cheap valve, it is likely to be made of cheap metal and that metal will bend/deform easily. So if you have a really nice needle valve, you likely will not want to close it all the way and risk deforming the needle or seat. But if you have a cheap, almost throw away valve, you may not care so much about ruining it but it will also be much easier to do that damage.
So the question to ask yourself is? Which do I want to risk, big expense or smaller expense but more likely. I don't like either option so I use a cutoff to close flow as they are made to be closed all the way.

 

The needle valves on these are not nice needle valves, they're rudimentary but get the job done. I started with citric acid/baking soda DIY using the exact same model in the video. I turned it off at night with zero issues. If you're using 2 liter soda bottles, they are rated for a surprisingly high PSI and will not explode. Plus, the citric acid/baking soda reaction, as beckyhiker mentioned, is not constant due to the need for it to feed from bottle 1 to bottle 2 for the reaction to occur. As pressure builds, it's not going to continue feeding, so your PSI will rise until the reaction is complete in bottle 2 and it will be far from the bursting point for that 2 liter.

Have a look see - How Much Pressure Can a Two Liter Bottle Handle? | Education - Seattle PI

You'll blow the caps off the bottle well before you blow the bottle.

You could get a cutoff as PlantedRich mentioned if you're so inclined. I imagine a cheap plastic one like what we use to regulate flow on air pumps would be sufficient.

 

Thanks for all the information! Very informative

Cheers