large bands in all pcr reactions including negative control - (Oct/24/2014 )

Hi,

I am having trouble with a PCR reaction. I am getting 3kb size bands across the board in all of my reactions. Including a negative extraction control and my negative water control. I have done everything to control for contamination. New water, primers, polymerase, new extraction kit and I cleaned all the surfaces in the hoods where I do the extractions and add the template. The master mix is made in a clean room. Is there anything else that could be going on with my PCR ? I don't know what do do next.

Did you swap all the reagents at the same time? If so, it is possible that your water source (not just the tube/bottle you use) is contaminated, can you get some DNA/RNA free water from somewhere to test. This water often comes in small tubes with reverse transcriptases.