I would be grateful if someone help me to correct my letter.
We would like to draw your attention to owner (Tower 6, 11/F, Flat D) complaint regarding the poor water quality on 1st Nov 2006. The captioned issue has been verified as a result of our observation in the flat. The polluted fresh water has been caused by the rusty water pipes after our verification shown on the attached photos.
We would like to seek your assistance in rectifying this problem as soon as possible in order to improve water quality.
We would like to draw your attention to the complaint made on 1st Nov 2006 by the owner of Flat D, 11/F, Tower 6, regarding the poor quality of the water received in the flat. Our investigation has shown that the pollution of the water has been caused by rusty water pipes. In verification, we attach photos of the problem.
We would like to seek your assistance in rectifying this problem as soon as possible.
Alternatively, the ending sentence could be phrased:
We would appreciate this problem being dealt with as soon as possible.