Infected in the Keg?

This is my second batch I have kegged. The first batch went great, it was a porter that had great texture, mouth feel, and was complimented by a Sr. Homebrewer. Now I have had my next batch (Imperial Stout) in the keg for just over a week and it is getting an off flavor. I am not sure how to describe it other than sour ammonia. I poured a couple of glasses out and it seemed to loose the taste after a few pours so I thought it was just me. Today I did the same thing and the odd flavor persisted.

I use starsan and took the keg parts off and sanitized them using a spray bottle, soaked them in a pan for a few minutes, and ran a gallon of dilluted starsan through the keg so I really hope it is not infected.

If it was the ABV of the beer it would just taste alcoholic, this tastes like someone spiked my drink with windex. Any suggestions?

Have you cleaned your beer line?
If the taste starts to decrease after pouring a few pints I would suspect that. Soak it bleach, rinse very well, star san and then try it again.

I will try that, but shouldn't running a gallon of diluted starsan through the lines before I keg do the trick?

Hey unless you've bar tended, cleaning your lines just takes practice! Cleaning tap lines requires either a slightly stronger than normal rinse or a small brush ran the ENTIRE way through the line followed by soaking. People with skunky beer normally have this funky paste coating the inside of their lines. When the beer sits in the line for more than a few seconds, the gunk turns the beer into what you're describing. Good luck, I hope this helps!

Another possibility is that your gas line has been contaminated. The way to prevent that is to have an in line check valve as close to the gas input connection on your tap as you can make it. Gas line contamination can occur if the keg pressure is higher than your gas line pressure. When you tap the keg, beer will flow into the gas line and potentially all the way to the regulator. Once there, every keg you connect the gas line to will become contaminated. Whenever I tap a keg I always release the pressure in the keg before I connect the gas line - and I always use a check valve. Sanke and golden gate taps have a check valve built in to them, but I never trust them. Hope that helps.

OctopusInk said:

I will try that, but shouldn't running a gallon of diluted starsan through the lines before I keg do the trick?

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Starsan is a sanitizing/disinfecting agent, not really great for actual cleaning. Soak the line with oxyclean, and maybe you can fit a string through it and tie off a piece of oxyclean soaked cloth in it.
Then rinse, and sanitize.

Well it seems that the Cleaning of my dispensing line did the trick, I have a thick malty and ammonia free Imperial Stout to enjoy for December. I have a Janet's Brown Ale fermenting and I will not make the same mistake again. Thank you for all your help and I will get some oxyclean to use from now on.