# [Wet Thumb Forum]-Device to avoid CO2 "end of tank dump" adverse effect



## BobAlston (Jan 23, 2004)

Ever since I started researching my high pressure co2 system, I had read horror stories about "end of tank dump". Apparently many regulators become unstable when the pressure drops from the normal 800 psi or so - when the liquid co2 runs out. Apparently what happens is that the output pressure increases from what you have set. Depending on various factors, this can cause an increase in co2 flow and kill fish.

One way to deal with this would be to put a "pressure regulator" between the regulator and needle valve. clippard makes several. They have one that dumps excess pressure and one that doesn't. For example, the MAR-1P-NR-2 is set for a max of 20 psi and does not do "self-relieving" (I think which means it does not dump the excess). Cost is $11.20. 
It would seem to me that this would TOTALLY avoid the output pressure increasing about the defined valve setting.

Anyone have such in place or something similar?

Bob


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## BobAlston (Jan 23, 2004)

Ever since I started researching my high pressure co2 system, I had read horror stories about "end of tank dump". Apparently many regulators become unstable when the pressure drops from the normal 800 psi or so - when the liquid co2 runs out. Apparently what happens is that the output pressure increases from what you have set. Depending on various factors, this can cause an increase in co2 flow and kill fish.

One way to deal with this would be to put a "pressure regulator" between the regulator and needle valve. clippard makes several. They have one that dumps excess pressure and one that doesn't. For example, the MAR-1P-NR-2 is set for a max of 20 psi and does not do "self-relieving" (I think which means it does not dump the excess). Cost is $11.20. 
It would seem to me that this would TOTALLY avoid the output pressure increasing about the defined valve setting.

Anyone have such in place or something similar?

Bob


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## imported_Mark (Mar 4, 2003)

Rapids Wholesale sells a regulator that bleeds out excess pressure to open air when you hit the end of the tank. I have used one of these for a year and it's very nice. Ran about $44.


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## Robert Hudson (Feb 5, 2004)

Or you can buy a low pressure regulator with a built in needle valve and a fixed working pressure, such as the Aqua Medic one









Robert
King admin
www.aquabotanic.com


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## BobAlston (Jan 23, 2004)

Mark - what is the model number of this device? sounds like it may be essentially the same thing. what I wrote about above was one that did not bleed off the excess pressure. but they also have one that does bleed off excess pressure. Same cost $11.20

Can I assume you have it mounted between the regulator and your needle valve?

Have your heard it "work"?
Bob


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## imported_Mark (Mar 4, 2003)

The part number is 9T852. I have not heard this device work, but I also have not had a major swing in ph since using it. Regardless, they say it has an internal relief valve and I believe them.


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## gsmollin (Feb 3, 2003)

How much "dump" are we talking about? My regulator "dumps" 2-3 psi at end of tank.


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## ekim (Jan 31, 2004)

> quote:
> 
> Originally posted by gsmollin:
> How much "dump" are we talking about? My regulator "dumps" 2-3 psi at end of tank.


Same here! 
All this extra equipment might make this more complicated than it needs to be!
In my situation there is no "dump" maybe a slight increase in bubble count (10%)!
I have never lost a fish... no solenoid or other misc. parts!


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## imported_Mark (Mar 4, 2003)

No extra equipment, folks. It's a regulator as you can see in the link provided







I picked this up with my first CO2 system as I was worried about the "end of tank dump" myself. All the equipment I have is this regulator, the tank, the tubing, a bubble counter, and a needle valve. I did it all on the cheap, so the parts are kind of tossed together, but the system works just fine for me.


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## BobAlston (Jan 23, 2004)

Mark -

Thanks. That regulator is the one I got with my $99 tank + regulator kit from them. So as long as the +15 PSI pressure won't cause a significant increase in co2 flow thru the needle valve, I guess we are all set.

So, a) if the +15 psi pressure would cause a problem; or b) for people whose regulator might allow an even higher pressure at end of tank: What I was thinking of was a valve, that you could use just after the regulator, that was engineered to allow a slightly higher max pressure. For example, my pressure is set on the regulator at 8 psi. I would guess that I could add the device per my 1st post, that would limit the pressure flowing to 10 psi. So regardless of how much higher the pressure got coming out of the regulator(in this case it should be able to go to 23 psi (8 + 15)before the built in relef valve kicks in), this valve would function.

Does this make sense or am I still missing something?

Bob


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## BobAlston (Jan 23, 2004)

The rapids wholesale 9T852 is the unit they sell in their BD435 $99 kit - which I purchased. The regulator is a TapRite 742 regulator (says so on the regulator). The TapRite literature confirms the internal relief valve if the pressure exceeds +15 lbs above the set pressure.

http://www.totalbeveragesystems.com/PDF%20Catalog%20Files/regulators/taprite_doublegaugeco2.pdf

Bob


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## gsmollin (Feb 3, 2003)

Dear Bob,

I have a Tap-Rite 740. Its end-of-tank dump is 2-3 psi, as I wrote before. The safety relief valves you refer to don't activate until the pressure is 15 psi above the setpoint. That would raise your 8 psi pressure to 23 psi. So that safety would not protect your fish from too-high CO2. It's only meant as a safety device for you, not your fish.

Now back to "dump". I have observed that the dump is always 2-3 psi, regardless of the setting on the regulator. So an 8 psi setting increases to 11 psi. Thats a 40% increase. If a 40% increase in CO2 is acceptable for you, then you are safe from CO2 dump. If that is too much, then raise the regulator setpoint until the dump is acceptable. For instance, setting the regulator to 15 psi would give an 18 psi dump. Thats only a 20% increase, and is relatively safe for the fish.


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## BobAlston (Jan 23, 2004)

Thanks gsmollin

What you said for how to adjust my pressure makes sense. 

Also I wrote TapRite and they confirmed in writing what your experience has been:
" The Tap-Rite regulator ( 742 ) which you have & are using, will have minimal drift ( less than 2 lbs. ) from full to empty CO2 tank."

I know a lot more now from when I posted my note. With your suggestions, I can set my system with little concern. 

Others, with regulators whose pressure at end-of tank increase more than 2 lbs may have more of an issue.

Thanks again.
Bob


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