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Telltale sign of imminent co2 tank emptying

2K views 9 replies 8 participants last post by  Grobbins48 
#1 ·
I installed a 20 lb co2 tank for my 75g 11 months ago, and it is still running. I don’t think it can last that long. How can I tell when it is imminently emptying out? I’m on travel often and don’t want it to empty during my absence.
 
#2 ·
The internal tank pressure should stay the same until the tank is nearly empty, and then it will fairly rapidly fall to 0. When you see it start falling, that's when you should start thinking about getting it refilled. A lot of variables go into how long it will take to go from pressure falling to empty tank, but FWIW, my 10lb tank takes over a week to empty once the pressures starts dropping.
 
#3 ·
In my experience, once it gets into the red zone (below 500psi) it goes pretty quick. I don't try to milk out every last drop and just go ahead an change it.

In a high tech tank, just a few days without CO2 can lead to some very quick changes. I keep a second filled tank on hand, but I am changing it out every two months. In your case, I'd pick a day when you have time and get it done sooner rather than later.

Pennies compared to everything else.
 
#4 ·
Unfortunately, my pressure gauges aren’t working right. The cylinder gauge always read 500 psi with no change, and I blew the working gauge by over pressuring it. I received replacement gauges from manufacturer, but want to wait and replace them at next refill. Lately, I noticed the bps and bubble size have shift moderately, and I had to adjust the regulator to achieve the same pH drop. Is it a sign of emptying out or normal response to change in summer temperature.
 
#7 ·
Do you just unscrew the old gauges and screw in the new ones by hand tightening? Do you need to put Teflon tape to seal the thred.

I haven’t done it yet because I hate to do leak test and readjust the injection rate that took me a long time to stabilize. Now that the injection rate is shifting and the tank is probably emptying, I may just do it.
 
#8 ·
Do you just unscrew the old gauges and screw in the new ones by hand tightening? Do you need to put Teflon tape to seal the thred.



I haven’t done it yet because I hate to do leak test and readjust the injection rate that took me a long time to stabilize. Now that the injection rate is shifting and the tank is probably emptying, I may just do it.


Yes and yes. Use the yellow Teflon tape specifically designed for gas.
 
#9 ·
For the short term, I would suggest weighing the tank and reg. The tank will have a tere weight stamped somewhere near the top where all the markings are located. This will be the empty tank weight and by weighting without the reg, etc. you can tell if you have a full tank of 20 or a near empty weighing only a couple pounds more than the tare weight.
To avoid having to remove the reg each time to check the level, I would also weight the reg, add the two readings together and that would let me know how much is left by simply weighting both together.
Point to keep in mind is that after the liquid portion is gone and that is what you weigh, there will still be a fair amount of gas left. Since you seem to be using a low quantity, I might expect the gas portion to last in the range of two weeks. But that is also very much a guess and you should not trust my guess too far!!!
 
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