When the water has been turned off, the water flow can disturb sediment in the pipes, which can then cause the water to appear to be dark in colour. I have been in contact with Thames Water regarding this and they have assured me that it is not harmful.
With the colder weather, Thames Water have also advised the following to help prevent water leaks:
• Check pipes – thaw frozen pipes with a hot water bottle or a towel soaked in water
• Bleed the radiators – use a radiator key to open the valve and release trapped air
• Look after your central heating – get your boiler serviced often and keep the heating on low when not at home
• Find your stop tap – these are usually found under the kitchen sink. Turn right to tighten and left to loosen
• Keep a plumber on hand – keep details of a reputable plumber on hand and make sure to check home insurance cover
In the instance that you see a leak, you can report it to Thames Water here, then phone a plumber immediately.
Please do keep an eye on my Twitter, where I am posting updates on the water issues as they arise.