[bkreiter]

Twice now I have keeged a beer, force carbonated, and ended up with a wicked lingering aftertaste. Never had an issue prior to this. I clean with PBW and in both cases let the PBW solution sit in the kegs for several days. The second instance I took the entire keg apart, cleaned, sanitized (star san), reassembled and kegged. Force carbonated by cooling keg to 38F, presurizing to 25, shaking for 10-15, returning to kegerator. In both instances I sampled the beer going into the keg and it was really good, just flat and warm. In both instances the flavor was present the very next day; totally undrinkable. If this was a bacterial issue, wouldn't it take more than 12-24 hours to be so prevalent? Advice?
Theories:
-Bad gas: Refilled cylinder at fire extinguisher place. They used a compressor machine rather than filling from a tank. This concerned me at the time... Better not be just compressed air! I was advised by a local beverage supply co. to use this vendor....
-PBW residue: PBW sat in keg for several days, rinsed with high pressure garden hose
-Gas line contamination....?

[zorch]

I know it can be hard to describe a bad flavor, but can you try and give us a bit more to go on?   

Do any of these descriptions come close?
http://www.howtobrew.com/section4/chapter21-2.html

[vorlaufthegreat]

Did you clean out your dip tube with a brush?

[gordonstrong]

-PBW residue: PBW sat in keg for several days, rinsed with high pressure garden hose

Was it a normal garden hose or a drinking water-type garden hose?  Regular garden hoses have a very distinctive plastic taste.  You know, tastes like hose (shut up, I'm serious).  If your rinse water is chlorinated, guess what?  You just added the two parts of chlorophenolic, one of the nastiest flavors there is.  "Medicinal" is probably the kindest thing to call it.  Tastes like chloroseptic throat lozenges.

[narvin]

Did you used to bottle before this?  If you don't cold condition in the primary/secondary before kegging, your flocculating yeast is going to be served first from a keg because of the dip tube, as opposed to being left behind at the bottom of the bottle.  This can also include some trub and bitter hop residue if you aren't careful when you siphon.  How was the last keg once you got halfway through it and it cleared up?

[euge]

Did you used to bottle before this?  If you don't cold condition in the primary/secondary before kegging, your flocculating yeast is going to be served first from a keg because of the dip tube, as opposed to being left behind at the bottom of the bottle.  This can also include some trub and bitter hop residue if you aren't careful when you siphon.  How was the last keg once you got halfway through it and it cleared up?

That's good. +1 Can we get a description of the wicked lingering aftertaste?

[bkreiter]

This is a hard one to describe because I've never experienced it. Perhaps medicinal, perhaps solvent, definitely some bitter going on. There should be some bitter in the second batch (DIPA), there's five ounce of hops in it....! The aroma was normal and pleasing. The off flavor is noticeable immediately on the sides and back of tongue. I took a big swig and the flavor stayed with me for the rest of the day....
While the problems with the two batches seem the same, I think they are different. I still have the first bad batch in the kegerator because I have not yet come to terms with the fact that it is bad. It's definitely contaminated (it's now cidery and cloudy). This batch was chilled to 38 for 24hrs before kegging.
The second batch might be ok after all. For some reason or another, I didn't chill this one. I poured out four glasses and tasted the fifth. The off flavor is diminished. I'll try it again tonight and report my findings
Thanks for the sage advice! Take home points for me, even if they weren't contributers:
-No more pvc garden hose, especially after it's been lying in the sun
-Dip tube brush necessary
-Always chill before kegging

[rabid_dingo]

-PBW residue: PBW sat in keg for several days, rinsed with high pressure garden hose

Regular garden hoses have a very distinctive plastic taste.  You know, tastes like hose (shut up, I'm serious). 

I have to say that I grew up in Mexico and Arizona. And let me tell you some hot days, you open up the
house spigot and drink out of that hose.. When you get that hose taste....(gasp)  Some of he most refreshing water when
the temps are 126*F outside. 25 years ago no one would have said boo. I don't believe I am in any danger...
I loved that taste.

And to the OP and RE: PBW and the dip tube take a look down the tupe in broad daylight. Best lighting you
can get. I never considered that the bend in my tubes (Ball-Locks) would allow sediment to settle on the
diagonal. Even with several days in PBW the gunk didn't move. Dip-tube brush is on my shopping list for the
next LHBS stop...

[euge]

Do everything you need to do to make yourself happy. Sounds to me like you got a case of the old "yeast-bite" right now.

[Kirk]

Sounds to me like you've been plenty careful about sanitation.  My guess is it's the CO2.

[oscarvan]

Did you taste it when you put it in the keg?

I taste my beer every step of the way..... after the boil going into the fermentation bucket, racking to secondary or kegging etc. That way you can say:"It was fine going in."

[bkreiter]

Woohoo! Batch number two is fine after all. Good old "yeast bite" indeed! By my fifth beer last night it was quite delicious. Mystery solved. I think the first batch that had this issue was yeast bit as well, but it also developed an infection of some kind.
Oscar, good advice, I taste every step of the way too. I mentioned in the original post that both beers tasted fine going into the kegs. Helps to narrow down any issues that develop, among other benefits...
No one seemed to have an issues with the method the fire extinguisher place used to fill my tanks?

[gordonstrong]

I get my tanks filled at a fire extinguisher place, but they always take it into the back so I don't know what they're doing with it.