I would suggest you to check the inline strainer/filter of your waterline,it could be clogged or broken ,allowing stain causing lumps of suspended particles settled in your overhead water storage tank.
Next would be to check your over head Water storage tank and clean if found dirty.It will take some time for the dirt to be dislodged from your pipes and will need flushing.
You may think about installing an inexpensive water filter with acrylic fibre cartridge and transparent housing so that you may see for yourself the exact cause and stop blaming the WM makers.

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Water storage tanks on roof tops and at ground level of most of the buildings in Doha are perennially neglected and can cause serious health hazards to the public if they are not periodically cleaned, says a report published in a local Arabic daily.
“The plastic and metal substances with which these tanks are made include chemicals which can disintegrate under extreme heat and mix with the water stored in it. Consequently the water consumed by the public from these tanks through their taps in apartments and villas can endanger health.”
In a random survey it was found that even most of the residents were unaware of which particular tank caters to each one’s apartment. They were also not aware of the various types of water storage tanks and the need to wash and clean them periodically.
The head of the safe environment cell at the Supreme Council for Health, Dr Mohamed Ahmed Ali, had recently issued a statement advising the public on the necessity of cleaning the water storage tanks every six months.