Posted: 13/07/2014 at 10:26
I never water my tomatoes until the leaves begin to flag - I then fill the pots to the top with water (I allow a 6-8" gap between compost surface and pot rim). I do this consistently - last summer I was only watering my tomatoes once or twice a week at the most - out of 27 plants and a huge crop of tomatoes I had only one fruit with BER.
Tomatoes do not need constantly moist soil, it impedes the take up of calcium which causes BER. I only fertilise my outdoor tomatoes twice - once when the first fruits have set, and again when the second truss has set. This helps prevent imbalances in the compost which can also contribute to BER.
Italophile is the expert and can explain the theory better than I can, but this article is helpful - you'll see it advises reducing watering to prevent BER http://extension.usu.edu/files/publications/factsheet/pub__8956068.htm
However, I agree with Italophile - the OP's tomato does not have BER