Liquid Purging Technique for Kegging- Inverting the Keg

[Brewmegoodbeer]

Hello all,

I just did a liquid purge for the first time last night (pushing out star san, replacing with co2). It went pretty smoothly and I was confident in the fact I effeciently removed all* (of course not ALL) oxygen from the keg before racking via closed system transfer. I then read this article: http://www.lowoxygenbrewing.com/bre...rging-transferring-stabilizing-finished-beer/

It states that leaving just 30 milliters of sanitizer solution in the keg will increase oxygen in the keg by 15 ppb. It mentions cutting the gas post as short as possible, to be able to invert the keg and push out the remaining sanitizer out of the keg. Is this a common practice for you “liquid purgers”? Im worried that the residual star san solution just adds oxygen and eliminates the entire point of this method.

 

[day_trippr]

fwiw, I cut all 16 gas tube down to a scant 1/2", but that has nothing to do with purging kegs.
As for purging, here's my method:

- make sure the Out dip tube is centered in its well at the bottom of the keg. Shortened Out dip tubes need not apply.

- set keg in large plastic tray
- hook a fill line to the In post from my Star San bucket and latch PRV open.
- fill until Star San foams out of PRV
- close PRV, and hook a drain line to Out post to a small catch bucket

- flip keg up-side-down. I made a "stand" from three short 2x4s to rest the keg upon its handles, making the posts accessible.
- continue filling keg until clear, bubble-free Star San appears in drain tubing while rocking keg back and forth from vertical

- disconnect drain tube, set keg upright, disconnect fill tube.

Given how much air can be trapped in the volume below the top of the lid/above the shortest dip tube I believe this is most effective way to purge a keg...



Cheers!

 

[GPP33]

Hello all,

I just did a liquid purge for the first time last night (pushing out star san, replacing with co2). It went pretty smoothly and I was confident in the fact I effeciently removed all* (of course not ALL) oxygen from the keg before racking via closed system transfer. I then read this article: http://www.lowoxygenbrewing.com/bre...rging-transferring-stabilizing-finished-beer/

It states that leaving just 30 milliters of sanitizer solution in the keg will increase oxygen in the keg by 15 ppb. It mentions cutting the gas post as short as possible, to be able to invert the keg and push out the remaining sanitizer out of the keg. Is this a common practice for you “liquid purgers”? Im worried that the residual star san solution just adds oxygen and eliminates the entire point of this method.

Not saying draining every last drop isn't a good idea but 15ppb is basically nothing and my kegs get out way more than the last ounce (which is what 15ppb is based on). I might try to see how much I can push from the keg and then measure how much more I can get from a cut gas tube but I'm guessing it's gonna be a very small amount.

 

[mongoose33]

I just purged a keg last night using the star-san-pushed-by-CO2 method. I have another way to get the residual star-san out of there:

When the star-san is pushed out of the keg, I pull the QD from the liquid side. Typically I use about 10psi to push out the star-san--which means I have a keg pressurized to 10-psi.

I take that keg over to the sink and attach a QD to the OUT post, a QD that has a 20-inch section of tubing attached. As soon as I attach it, of course, the CO2 starts blowing out through the tubing. I rock the keg so the escaping Co2 takes the star-san with it out the tube, such that by the time the keg is depressurized, no star-san is left.

In my Torpedo kegs, the dip tube is in a depression at the outside of the keg, so I just tilt the keg toward that post, the star-san gathers there, then up the dip tube it goes. With soda kegs, the depression into which the dip tube extends is in the center so I let the keg sit flat.

In either case, a little rocking of the keg and that star-san is gone.

 

[SanPancho]

to answer the OP's original question- its a fairly common practice among the LoDo and NEIPA crowd. two reasons- yes, cutting gas tube short makes it easy to get out last of the star san/water mix. (or shaking, or crazy setups as noted above) but also it helps to make sure you really do purge all the air from the keg.

if you think about a keg lid, the prv opening typically sits a good 1/2 inch below the main lid surface. that means you can have a pocket of air trapped in there even if you do the "spurt out the PRV" method like above. but if you cut the tube short and tilt the keg, you can get the air to wander over towards your gas tube. i havent bothered to try but some guys have been able to rig up their sink or water line to the liquid in side so that the water entering the keg will push the air out of the gas port if you tilt the keg at an angle with the gas QD pointing upwards. thats as good as you're gonna get to 100% liquid-purged as i understand it. the stupid faucet in my apartment doesnt seem amenable to that, so instead i just fill the keg literally to the top with water, open the poppets to let any air out of the tubes, gently slide the lid in trying to avoid trapping any air, and then close it up and purge. as noted above, lots of ways to skin a cat. but the cut dip tube definitely helps get all the air/star san out.

as for the question of whether star san will ruin your LoDo attempt, i would only say that those LoDo guys are pretty serious about it, so dont dismiss it. but like all things in homebrewing, its sort of a question of whether the effort is worth it to you.

if you have the space- do a side by side and see how it goes. or run same recipe twice and see if you notice the difference.

 

[mongoose33]

I'm adding this for those who are concerned about getting the last of the oxygen out of the keg before sealing it.

When I push star-san into the receiving keg, I leave off the lid. When the sending keg is starts pushing CO2 through the line, of course there are bubbles. In fact, if you do nothing you'll get an eruption of Star-san, so you have to watch and disconnect quickly so you don't get that.

I'll just connect/disconnect that jumper to create bubbles (but no eruption) until they start coming out of the keg. Those bubbles will fill the space under the lid, inside the keg, everywhere.

Guess what those bubbles contain? Yeah, CO2.

So at this point, with the bubbles coming out I'll reinsert and seal the keg. If I do this right, there is nothing in the keg except star-san and bubbles, which of course don't contain air, they contain CO2.

I don't worry about short dip tubes or anything else. The next time I need a purged keg, I push the star-san out of this one, and of course the only thing in it is CO2, plus a tiny bit of residual star-san. I purge that out using the method in the post above.

 

[SanPancho]

Do you purge the star san keg before you fill it? Cuz any air in that keg will transfer to the next one- either in solution or in the bubbles.

 

[mongoose33]

Do you purge the star san keg before you fill it? Cuz any air in that keg will transfer to the next one- either in solution or in the bubbles.

Purge with what? I always push the Star-San into the next clean keg. It's being pushed by CO2. Since I closed it up on bubbles, there is no air in there. So when I push out the Star-San, I'm just replacing the star-san with CO2.

The keg to which I'm transferring Star-San starts out full of air, but the Star-San displaces that, and I end up with a keg with no air in it.

It's actually disingenuous to say there's no oxygen in it, because the star-san had dissolved air in it. But it's the best I can do.

 

[SanPancho]

Exactly. Still gonna carry over air and dissolved o2. But in theory you could do it a bunch of times and keep lowering the ppb of o2 at each transfer if you have a reservoir for the star san and reuse it.

Personally I find it overkill to go that far, but if folks really wanna shoot for no o2 I guess this stuff matters to them. Hell, I don’t even bother with star san, just water. So no bubble for me, just filling to the brim. At the end of the day it’s variations on n same general technique I guess.

 

[Brewmegoodbeer]

What do you guys think about using saniclean instead of starsan to liquid purge kegs? It foams alot less. Im thinking the foam should be “feared” in this process bc guess what that foam is? Oxygen bubbles. There is no way to get all the foam out of the keg when doing this with star san. Forums and forums of both homebrewers and breweries alike discuss using saniclean in place of starsan in places where foam is not desired such as CIP and bottling. I think im going to lower my dip tube to the bottom center of keg so virtually all water w/saniclean is our of keg when purging.

Also the mention of a little oxygen being left in keg due to way lid is made. If you fill keg through liquid out post and then burp keg 2 or 3 times post filling I don’t see this being much of a problem.

 

[mongoose33]

What do you guys think about using saniclean instead of starsan to liquid purge kegs? It foams alot less. Im thinking the foam should be “feared” in this process bc guess what that foam is? Oxygen bubbles. There is no way to get all the foam out of the keg when doing this with star san. Forums and forums of both homebrewers and breweries alike discuss using saniclean in place of starsan in places where foam is not desired such as CIP and bottling. I think im going to lower my dip tube to the bottom center of keg so virtually all water w/saniclean is our of keg when purging.

Also the mention of a little oxygen being left in keg due to way lid is made. If you fill keg through liquid out post and then burp keg 2 or 3 times post filling I don’t see this being much of a problem.

I'm scratching my head on this one. If you check back on post #6, you'll see when you use CO2, the bubbles are CO2, not air with oxygen, and thus bubbles in this case are a feature, not a bug.

If you're sanitizing in place, fewer bubbles are desirable. For purging a keg, I think Star-San is perfect.

 

[Brewmegoodbeer]

I'm scratching my head on this one. If you check back on post #6, you'll see when you use CO2, the bubbles are CO2, not air with oxygen, and thus bubbles in this case are a feature, not a bug.

If you're sanitizing in place, fewer bubbles are desirable. For purging a keg, I think Star-San is perfect.

When filling the keg full with water and star san, the spashing creates foam which indeed is bubbles filled with oxygen, unless the keg is fully purged of oxygen before filling the keg with water (which wouldn’t make any sense to liquid purge in the first place if that were true). You then push out the star stan solution with co2 and push out as much as you possibly can. Knowing how foamy star san is, you can guarentee that not all that foam is out of the keg after the liquid is completely pushed out of keg. Yes, co2 bubbles were made in the process, but no way all those bubbles filled with oxygen from initially putting the star san solution into the the top of the corny are all gone. I think a low foaming sanitizer would help with this issue, such as saniclean or IO Star.

 

[mongoose33]

When filling the keg full with water and star san, the spashing creates foam which indeed is bubbles filled with oxygen, unless the keg is fully purged of oxygen before filling the keg with water (which wouldn’t make any sense to liquid purge in the first place if that were true). You then push out the star stan solution with co2 and push out as much as you possibly can. Knowing how foamy star san is, you can guarentee that not all that foam is out of the keg after the liquid is completely pushed out of keg. Yes, co2 bubbles were made in the process, but no way all those bubbles filled with oxygen from initially putting the star san solution into the the top of the corny are all gone. I think a low foaming sanitizer would help with this issue, such as saniclean or IO Star.

Well, I think there is a misunderstanding here. Unless you want to argue that that there is oxygen in the water (which there is, unless it was pre-boiled to eliminate that oxygen). But the bubbles you see above in post #6 are CO2, not air.

 

[day_trippr]

[...]There is no way to get all the foam out of the keg when doing this with star san.[...]

I don't think this is true. When I'm done filling my kegs the run-out is totally clear, so there is no foam.
And when I'm done blowing the Star San out, there is no foam - it never had a chance to form.
But let's say there was foam after emptying - clearly the bubbles would be filled with CO2, not air...

Cheers!

 

[Brewmegoodbeer]

Unless the keg you are pouring the star san solution in is completely purged of oxygen before hand, any splashing of the starsan will create foam and foam will be oxygen filled. Pushing the solution out will leave residual foam in keg just like sanitizing anything with star san: foam is usually left on the walls of the object. Youd have to wait maybe an hour or so until the foam slowly dissipates and turns into liquid, then purge that out.

 

[Brewmegoodbeer]

I almost want to watee purge a keg with star san, then open it up to show that there will still be foam on the inside walls lf the keg. Truth is some of it will be foam made from co2 and some will be from oxygen (like i keep saying, unless the vessel transferred from was completely purged of oxygen. I personall put star san in, then put a hose in my keg to fill with water before sealing. There is no way that the foam here is not made from oxygen. Residual foam left in keg after i purge all liquid will dicipate and oxygen will be released from foam. Maybe this is all way over thought, and maybe im even wrong, but either way, im now going to use 1 step cleanser (a no rinse low foaming solution) to water purge kegs.