Join Date: Oct 2007
Location: Ontario, Canada
A chelve valve is just an extra precaution. It's not neccessary but highly recommended. Like you will still be able to do DIY co2, but just in case so tank water or yeast/sugar water don't mix, or tank water back syphons onto the ground.
You put a check valve in between the bottle and tank, so cut the line and connect it in between.
Some things to take note of:
1. Make sure you get a quality check valve, last thing you want is a wonky check valve.
2. Also, make sure it's pointed the right way as you don't want any exploding pop bottles. It nearly happened to me before, I hooked up my DIY co2, was wondering where the co2 was. Turns out check valve was on backwards, the three 2l bottles nearly exploded. You can check by blowing into one end. If air passes through, that's the direction co2 should flow, from bottle to tank, not other way around!
3. Another thing is sometimes when you disconnect a checkvalve water back syphons, gushing water out onto the room, so be careful of that too.
I have used it on some set-ups and not on others. It really depends, it is highyl recommended though.
Oh yeah, if you are actively diffusing the CO2 (such as through a powerhead or impeller), I highly recommend one. Why? Sometimes the suction power of the active diffuser is so strong it out performs the amount of co2 that is produced. What ensues w/o a checkvalve is that all the air in the bottle is sucked out, then all that yeast/sugar water is sucked into the tank. Not a pretty sight. Fish will die, the yeast doesn't go away forming gunk all over your tank.