It seems a hospital nearby is having some work done on its plumbing and this has affected the neighbouring apartments. We will not receive hot water again until July 18 - which means it will have been shut down for 10 days.
Muscovites are used to having their hot water interrupted every summer. In an exasperating vestige of Soviet centralisation, hot water is provided by a number of plants around the city. These are are shut down for up to 10 days in the warmer months for cleaning and maintenance. For many, the incentive to shower decreases with the water temperature and the Metro becomes the Sweatro - a transportion system for millions of unwashed armpits.
There is often discussion about whether Moscow water is safe to drink. The city says that the water is clean. I'm not a chemist, so I can't offer an informed opinion. I suspect, judging by what has come out of our hot water tap the past few days, that some of the pipes may be in a sorry state. So while the water may leave the treatment plant potable, who knows what condition it is in by the time it arrives.
I have also noticed that all of the Russian employees where my wife works only drink bottled water - until I see them drink from the tap, I certainly won't.