Hi all thanks for the replies.
I am indeed about to go out and buy a new bucket to see if that does not fix the problem.
But that still does not explain how I managed to get two good brews in the middle of all the off ones. One of these was a pretty low-gravity affair, so I would have picked up any off tastes if there were any.
Here is my brew and cleaning process, in case the problems arise there. I brew in a kettle made from an old copper geyser, in which I installed two kettle elements. I put the grains in a bag in the kettle. As there is plenty of space in the kettle, I use the full amount of water that will go into the fermenter and do a no-sparge mash. I then remove the bag and then boil in the same kettle. After the boil, I put the immersion chiller in the kettle and from the tap at the bottom of the kettle, the brew goes straight into the fermenting bucket. As we do not get Starsan here in South Africa, i have experimented with bleach, a combination of bleach and vinegar, as well as the locally-available Perasan. I use the sanitizers in the ratios described in these forums and elsewhere. I put three gallons of the solution in the bucket, and insert all the equipment I would need for the brew. I also clean all the areas of the bucket not in contact with the solution, as well as the airlock and lid.
After bottling the brew, I ensure that the lid is closed very securely. I am sure that it is a good seal, as there is vigorous bubbling in the airlock. Despite all these precautions, I am left with a sour, vinegar taste in the majority of my brews. Any suggestions of where I might be missing the mark would be greatly appreciated, because right now I feel like I am in the business of manufacturing expensive salad dressings!
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