Apologies if this has been covered before: despite the syphon in our toilet cistern having been serviced a number of times by qualified plumbers (replacement of outlet valve seal and clip, etc), water continues to run down the back of the inside of our toilet bowl, as evidenced by the 'toilet tissue' test. The toilet is little more than ten years old and is in good condition.
Does anyone please have any clues as to what might be happening? Thank you - MmM