Why do you have to purge? - Home Brew Forums
Register Now For Free!

Home Brew Forums > Home Brewing Beer > Bottling/Kegging > Why do you have to purge?

Reply
 
Thread Tools
Old 02-17-2013, 11:27 PM   #1
jonmohno
Registered User
Recipes 
 
Nov 2010
Corn, High Fructose Corn Fortress, IA
Posts: 5,847
Liked 417 Times on 367 Posts



Just got a new 3 gallon keg kit, I have 2 gallons of Ranger-cloneish in it, not knowing about volume to psi levels, I set it @ 16 thinking I only need half for doing the quick method. I believe Im wrong about that and should have just set it @30 after further researching. Anyway....

Its been 30 hrs and Im wanting to check it, my first glass will be wasted anyway with sediment due to some "hard times" racking from using loose leaf hops. I got more sediment in it than I was bargoning for.I used a hop bag on my siphon to filter and that didnt work so I took it off and got hop leafs stuck in my auto-siphon- I eventually got most of it in my keg loosing a good 3-4 beers. I should have just funnel/strained the last of the carboy that I couldent siphon. Not to mention the little black-flapper -valve came out of the siphon. NOw I got to find a way to put it back in.

So why do I need to purge it before setting it to 10 then dispensing some? And do I need to purge all of it till it stops? Then set it at 10 before dispensing some? I was going to not purge it andsee what happens but I thought Id better ask first since Ive never kegged before.

 
Reply With Quote
Old 02-18-2013, 12:22 AM   #2
jonmohno
Registered User
Recipes 
 
Nov 2010
Corn, High Fructose Corn Fortress, IA
Posts: 5,847
Liked 417 Times on 367 Posts


Well,I purged it.Set it to 8 and its carbed and looks like nitrous looks. I hate to say it but its almost too hoppy at this point but its carbonated. So do you just leave the lines open and gas on? set at serving pressure? or do I need to close the valve/valves since its carbed? Do you shut your lines when its carbonated or do you need to keep them open @10psi- until the keg is gone even if you drink it over a period of 2 months?

 
Reply With Quote
Old 02-18-2013, 12:35 AM   #3
davekippen
 
davekippen's Avatar
Recipes 
 
Dec 2011
Grand Ledge, MI
Posts: 1,258
Liked 165 Times on 127 Posts


You purge to get the oxygen out. The CO2 is "heavier" so in theory when you fill the keg with gas, the oxygen goes to the top. Purging blows the oxygen out. Do it a few times and walla you have no oxygen to oxidize your beer. Just pure CO2 goodness.

You can keep the gas on or off once its carbed, up to you. Unless you have a leak you are not using any more gas by leaving it on. The beer/headspace will only take so much gas, then no more.
__________________
Quote:
Originally Posted by JonM View Post
Zombie yeast wants graaaaaaaiiins!!!!!!
Hit me on Untappd https://untappd.com/user/davekippen

 
Reply With Quote
Old 02-18-2013, 12:35 AM   #4
mattd2
Recipes 
 
Sep 2009
Papamoa, New Zealand
Posts: 3,770
Liked 319 Times on 254 Posts


How long did you actually wait between your first post and just doing it?
Yes, you need to leave the gas on at your serving pressure.
The reason for purging is if you tried to pour a beer at 30 PSI it would shoot out too fast and you would be left with just foam in your glass. no need to completely purge to 0 PSI and then pump it back up. I ususally turn the reg back down to "0", then purge till it drops just under my target temp, then wind the reg back up.
but most of the time I just set and forget for 2ish weeks.

 
Reply With Quote
Old 02-18-2013, 12:54 AM   #5
jonmohno
Registered User
Recipes 
 
Nov 2010
Corn, High Fructose Corn Fortress, IA
Posts: 5,847
Liked 417 Times on 367 Posts


Quote:
Originally Posted by davekippen View Post
You purge to get the oxygen out. The CO2 is "heavier" so in theory when you fill the keg with gas, the oxygen goes to the top. Purging blows the oxygen out. Do it a few times and walla you have no oxygen to oxidize your beer. Just pure CO2 goodness.

You can keep the gas on or off once its carbed, up to you. Unless you have a leak you are not using any more gas by leaving it on. The beer/headspace will only take so much gas, then no more.
Thanks but I was talking about purging it using the quick carb/few day method before you serve it. Yes I did purge it once I initially racked it and gassed it up. Thanks.
I set it at 8.It seemed to be shooting out fast foamy still even after purging and turning it down to 10. Im now on my second short pour already.

Its weird it shot up to 20 psi when I opened the air line valve after I first purged it and I had thought I was turning it down, I was able to get it back down to 10 shortly though. That confused me,does this mean I need to purge it again a little since it shot up to 20-then I just turned it down. Does that mean there is 20 psi in the beer now and just 10 psi in headspace since the regulator was reading 10? Well I did turn it to 8 now because of how fast the second short pour was coming out. Or do I really need to keep it at 10 for the duration?

 
Reply With Quote
Old 02-18-2013, 01:10 AM   #6
brewingmeister
Recipes 
 
Apr 2009
middle of nowhere
Posts: 1,910
Liked 183 Times on 136 Posts


Venting after force carbing prevents having a mess. Without venting the beer would rocket out of the tap, make a bunch of foam and end up flat.
Btw, 16 psi isn't very much to force carb for a day especially if it wasn't already cold.
__________________
............Alright Brain, you don't like me, and I don't like you. But lets just do this, and I can get back to killing you with beer......~Homer

 
Reply With Quote
Old 02-18-2013, 01:31 AM   #7
jonmohno
Registered User
Recipes 
 
Nov 2010
Corn, High Fructose Corn Fortress, IA
Posts: 5,847
Liked 417 Times on 367 Posts


Quote:
Originally Posted by brewingmeister View Post
Venting after force carbing prevents having a mess. Without venting the beer would rocket out of the tap, make a bunch of foam and end up flat.
Btw, 16 psi isn't very much to force carb for a day especially if it wasn't already cold.
I cold crashed it.It was cold when I racked it,then it went straight to the fridge.It is 2 gallons in a 3 gallon keg-if that matters I dont know. Should I turn off the small red line valve,purge it again, then open the valve with not touching the regulator which is now set at 8 and see if then comes out flat?

 
Reply With Quote
Old 02-18-2013, 01:44 AM   #8
mattd2
Recipes 
 
Sep 2009
Papamoa, New Zealand
Posts: 3,770
Liked 319 Times on 254 Posts


I think what he is saying is you might not be carb'd fully yet. I would leave it at 8-10 (whatever your desired CO2 volume requires) for another week, gas on the whole time. From what you said about how it looked when you did pour it I would say undercarbed.
As you mentioned if force caqarbing most would set at 30 psi for a day, and then drop to serving pressure.

jhoneycutt Likes This 
Reply With Quote
Old 02-18-2013, 01:46 AM   #9
brewingmeister
Recipes 
 
Apr 2009
middle of nowhere
Posts: 1,910
Liked 183 Times on 136 Posts


Well you're already pouring brews and you only had it set to 16psi so I wouldn't vent anymore. Just set it to whatever you want to serve and call it a day. Better to let it be undercarbed for a few days than to have to deal with overcarbing.

The colder the liquid the quicker it absorbs co2 so starting it cold helped.
__________________
............Alright Brain, you don't like me, and I don't like you. But lets just do this, and I can get back to killing you with beer......~Homer

 
Reply With Quote
Old 02-18-2013, 01:53 AM   #10
brewingmeister
Recipes 
 
Apr 2009
middle of nowhere
Posts: 1,910
Liked 183 Times on 136 Posts


Yeah I do think it is undercarbed and I would be hesitant to crank up the pressure because of the likelihood of overcarbing at this point. It is only two gallons so it shouldn't take more than a few days to be where you want it since you are most of the way there.
__________________
............Alright Brain, you don't like me, and I don't like you. But lets just do this, and I can get back to killing you with beer......~Homer

 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
how does one purge with C02? Thehopguy General Techniques 3 01-24-2012 04:59 PM
How much do i purge? Gustavo Bottling/Kegging 6 09-28-2011 03:37 PM
Beergun, CO2 purge ol' rummie Equipment/Sanitation 6 07-24-2009 06:47 PM
CO2 Purge in carboy? briewer2 Equipment/Sanitation 2 04-21-2009 11:11 PM
purge air from secondary fleas Beginners Beer Brewing Forum 3 04-12-2007 05:02 AM


Forum Jump