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Re: Aquatic Plants Digest V4 #702

Dave G. wrote:
"If you have a device (such as an Eheim diffusor) that runs at 15psi (more
or less), and you encounter an unprotected dump at end of tank, the input
to the Eheim will rise from 15psi to maybe 150 and a huge dump will occur
thru the Eheim."

That's a HUGE drop Dave and with some regulators highly unlikely! Check out 
http://www.aquabotanic.com/regulator.htm and then scroll down to the section 
called "CO2 Regulator Comparison Chart". There you'll see that the biggest 
number available for the outlet pressure rise is 1.78 psig/100 psig for the 
Air Products High-Purity E11-N145 . I'm not saying that your scenario can't 
happen. But with some regulators it is unlikely. So let's do some math for 
the numbers you provide above.

If the rise went from 15 psi to 150 psi that's an increase of 135 psi.

We divide 135 by 1.78 to see how many times the cylinder pressure has gone 
down by 100 psi.

135 / 1.78 = 75.84

So this means that the cylinder pressure has gone down 100 psi nearly 76 

To see what the final psi that results in we multiply 76 by 100 psi and then 
subtract that number from the 830 psi that the CO2 cylinder pressure is in 
at 70 degrees Fahrenheit.

76 x 100 psi = 7600
830 psi - 7600 psi = -6770 psi

So at the end the pressure inside the tank will be -6770 psi and the CO2 
cylinder would have imploded!! I find this highly unlikely but if you have 
some sort of website or book that you can show me that proves your point 
then I would be willing to take back what I said. Either that or I didn't 
understand what you said. At most the regulator mentioned above would allow 
an increase of 14.24 psi at the end-of-tank scenario. So this means that 
when the cylinder is nearly empty you have about 29.24 psi going out of your 
regulator if you started out with 15 psi.

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