My water pipes have a weak live current?

I have been told by a plumber who repaired my boiler that I have reverse polarity in the downstairs ring main. This became apparent when the boiler wouldn't work when reconnected to the downstairs ring main (I had it connected upstairs prior to the repair). The 15mm water pipes have a weak current both upstairs and downstairs when the downstairs ringmain is on. If I disconnect the fuse for the downstairs ring main, the pipes are not live. Could anyone please shed light on this issue for me?