Author Topic: Dispensing Soda  (Read 4522 times)

Offline darkmorford

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Dispensing Soda
« on: August 16, 2011, 09:25:59 AM »
I mixed up some "homebrew" soda (using one of the SodaStream syrups) in a corny, and I've got it under pressure to force-carbonate. I don't have a way to keep kegs cold yet, so it's at room temperature (74–78°F). I know that most sodas are carbed to 3.7 volumes or so, and according to all the tools I can find—BeerSmith's Carbonation Tool and a few online tables/calculators—that means putting it under about 55 psi of CO2. That much isn't a problem; my regulator goes up to 60 psi.

What's worrying me a bit now is getting it out of the keg. From what I understand, in order to balance out the 55 psi I'm going to need almost 20 feet of 3/16" vinyl hose! Not all that expensive, true, but that's a lot to have lying around. Of course, chilling the corny would reduce the pressure needed and, by extension, the length of the hose, but that's not really an option at this point due to space and budget. Is there anything else I can do to avoid such a long piece of tubing?

Offline Joe Sr.

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Re: Dispensing Soda
« Reply #1 on: August 16, 2011, 09:30:09 AM »
I don't recall the length I have hooked to my keg of root beer, but it's long enough that I coiled it up and secured it with zip ties so it won't uncoil.

I suppose you could try a smaller diameter tubing.
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Offline Bret

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Re: Dispensing Soda
« Reply #2 on: August 16, 2011, 11:15:01 AM »
Can't you just reduce to serving pressure once it is carbed up like you would a beer? Am I missing something?
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Offline darkmorford

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Re: Dispensing Soda
« Reply #3 on: August 16, 2011, 02:08:55 PM »
My understanding (and if I'm wrong, someone please correct me) is that dropping the gas pressure to the 10–12 psi typical for beer serving would cause the soda to degas. Even if I were able to chill the keg to 38°, I'd need 24 psi to maintain the 3.7 volumes of CO2. With a lower pressure I'd end up with flat soda.

Offline narcout

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Re: Dispensing Soda
« Reply #4 on: August 16, 2011, 03:01:24 PM »

Offline darkmorford

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Re: Dispensing Soda
« Reply #5 on: August 18, 2011, 12:29:51 AM »
Well, I seem to have made a pretty big mistake. Even though 20 feet of hose does a good job of restricting the flow rate, I forgot to consider that there's still 50–55 psi coming out of the end of it. And the Cobra picnic taps just aren't made to deal with that kind of pressure. (Don't ask how I found that one out.) So now I've got a half-full keg of knockoff soda and I don't know how to dispense it. I'm guessing the standard tap faucets can contain the high pressure, but I don't have a place to mount one of those.

Offline darkmorford

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Re: Dispensing Soda
« Reply #6 on: August 20, 2011, 04:06:59 PM »
In the name of experimentation, I took a 6' length of 1/4" tubing I had (which, according to the numbers I have, should compensate for about 5 psi) and stuck a Cobra tap on it. I dumped the pressure in the keg and re-pressurized to 6 psi, to account for the hose and height difference. While the picnic tap was able to contain this lower pressure, the pour was nowhere near consistent. The soda came out in fits and spurts, and I still wound up with a glass of foam.

This is my first time working with a keg, and clearly I'm doing something wrong. These things are literally made for soda dispensing, and if I can't get it to do what it's built to do, I'm not sure I'm willing to put a batch of beer in there. I'm thinking about getting a faucet setup just so I have something more reliable than the plastic picnic taps, but I'm no longer confident that I know what I'm doing with this hardware.

Help?

Offline dbeechum

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Re: Dispensing Soda
« Reply #7 on: August 21, 2011, 09:35:09 AM »
Something else to play with - Resistive Gate - made by a fellow club member to make high pressure pouring smoother.
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Offline Joe Sr.

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Re: Dispensing Soda
« Reply #8 on: August 22, 2011, 01:05:47 PM »
Well, I seem to have made a pretty big mistake. Even though 20 feet of hose does a good job of restricting the flow rate, I forgot to consider that there's still 50–55 psi coming out of the end of it. And the Cobra picnic taps just aren't made to deal with that kind of pressure. (Don't ask how I found that one out.) So now I've got a half-full keg of knockoff soda and I don't know how to dispense it. I'm guessing the standard tap faucets can contain the high pressure, but I don't have a place to mount one of those.

Umm.  You may have 55 psi in the keg, but the pressure at the tap should be significantly less by the time the soda travels the 20 foot of hose.

I haven't had ANY issues with my root beer keg and the cobra tap, and this keg has been more or less full and dispensing for at least 4 years.

I don't think I'm at 50 psi, but it's got to be 40+.

Maybe something else is going on.  Especially since you say your pour is inconsistent and goes in fits and spurts.  Perhaps something is restricting the flow in the keg.  Are you sure the dip tube is clear?

You also might try pouring into a pitcher (or growler) and see if it settles down after the first pint.  I believe that all of the soda in the line will be at somewhat of a different pressure than the soda in the keg.  I find with all my kegs that the first pint pours somewhat foamy and then the pour settles down.

Bottom line, if you've got issues with the pour you will have the with a Perlick faucet just as you have them with a cobra tap.  The faucet is not/should not be the issue.
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Offline darkmorford

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Re: Dispensing Soda
« Reply #9 on: August 24, 2011, 03:29:11 PM »
The reason I concluded that the Cobra tap couldn't take that amount of pressure is because of what happened the first time I hooked it up. I had the keg at 55 psi (with the CO2 hooked up at the same pressure), 20 feet of 3/16" vinyl tubing, and the picnic tap at the end. As soon as I stuck the QD on the liquid-out post, I had soda spewing out of the tap even without me holding it open. The sheer pressure at the tap end of the hose was enough to force the valve open and release the liquid. I suppose it's possible that my LHBS sells a low quality picnic tap and that a better one would be able to contain that pressure, but I'm willing to give them the benefit of the doubt.

I purchased one of the QD-to-faucet rigs I linked earlier, and the standard rear-valve faucet is holding up to the 55 psi just fine. Of course, without any hose behind it, the soda blasts out and I get a full cup of foam. I've got an inexpensive (chrome-plated brass) shank on the way so I can put some hose between the keg and faucet, and I'll report back on how that experiment goes.

Offline tschmidlin

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Re: Dispensing Soda
« Reply #10 on: August 24, 2011, 04:06:32 PM »
The problem is that 20' of 3/16" tubing isn't enough for 55 psi.  If the pressure at the picnic tap is low enough to get a good pour the tap will have no problem holding it.  For 55 psi I would start with a much longer length of 3/16" tubing.  I know it is supposed to restrict 2.2 lbs per foot (so the 20 feet was 5 feet too short by that measurement) but in my experience it is something less than that.

Hook your system up with what you have, and take the pressure off of the keg.  Slowly add pressure until you get the pour that you want.  Check the pressure.  Then just do desired serving pressure (55 psi) divided by current serving pressure (30 psi?  You have to check the gauge) times the length of the hose you used (20 feet) to get the length you should use.

So if 30 psi is accurate, 55/30*20 = 36.7 feet of tubing.  Given that measurement, I'd start with 38 feet and cut it off 6 inches at a time until you get the pour you like at 55 psi.

You can also mimic a longer hose using the resistance gate that Drew linked to.
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Offline darkmorford

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Re: Dispensing Soda
« Reply #11 on: August 24, 2011, 04:21:12 PM »
The problem is that 20' of 3/16" tubing isn't enough for 55 psi.  If the pressure at the picnic tap is low enough to get a good pour the tap will have no problem holding it.  For 55 psi I would start with a much longer length of 3/16" tubing.  I know it is supposed to restrict 2.2 lbs per foot (so the 20 feet was 5 feet too short by that measurement) but in my experience it is something less than that.
That probably explains it. I was using the Draft Beer Quality Manual and the table in there actually lists the 3/16" tubing at 3 lb/ft, so I figured that, if anything, I had a couple feet too much hose. If the restriction is as low as 2.2 lb/ft, there's definitely an issue.

I'll start playing around with the pressure once I get this shank and other stuff in. There's gotta be a point where I get a good pour and good carbonation without having a ton of hose around. Yay experimentation. >_>
« Last Edit: August 24, 2011, 04:37:15 PM by darkmorford »

Offline tschmidlin

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Re: Dispensing Soda
« Reply #12 on: August 24, 2011, 04:26:07 PM »
The DBQM is an excellent resource, but the numbers they supply are off IME.  The 2.2 comes from morebeer, and even that is high from what I've seen.
Tom Schmidlin

Offline darkmorford

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Re: Dispensing Soda
« Reply #13 on: August 29, 2011, 01:29:24 PM »
Still waiting for the shank hardware to come in (FedEx says Wednesday), but in the interest of getting more information out there I figured I'd share this old BYO article I found on balancing a draft system. Going by those numbers, I should only need to drop 46–50 psi through the hose, not the full 55 psi. Though I still might not have enough if the resistance is much lower than 3 lb/ft.

Incidentally, does anyone know if it's possible to use a standard pressure gauge (like the ones on regulators) to measure liquid pressure? The article claims that 5 psi at the tap is ideal, and I was thinking it'd be nice to have a way to objectively figure out how close I'm getting to that. (If I can't use a regular gauge, what do you recommend for testing liquid pressures?)
« Last Edit: August 29, 2011, 10:11:30 PM by darkmorford »

Offline darkmorford

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Re: Dispensing Soda
« Reply #14 on: August 31, 2011, 05:49:07 PM »
Okay, this is really strange. After my shank hardware showed up, I got that all assembled and tested it out. Even with the 20 feet of tubing I was getting a really fast pour with a lot of foam. So I went to Lowe's and picked up a water pressure gauge along with the necessary fittings to adapt that to a 1/4" flare. I stuck that assembly onto the faucet end of my tubing, dumped the pressure in the keg, then slowly starting bringing the pressure back up. Shockingly, it looks like my 20 feet of hose is only dropping 5 psi! I really don't know what to make of this, since that would mean my 3/16" vinyl is only restricting at a rate of 0.25 psi/ft! Can anyone explain what's going on here?