[nudephil (OP)]

Kathy sent in this:

Why is there a brownish residue in our water after it has been boiled and stored in glass bottles? The bottles and kettle are also being discoloured.

I thought it was the kettle so I purchased a new one and now the bottom of the kettle is being stained. Could this be  remnants of the sewage system? I am concerned that the consumption of this water may not be healthy...

Any ideas?

[Janus]

Most likely mineral deposits.  If you have hard water, this can happen. It is also possible that the ph of your water is a bit on the acid side, and boiling in a metal pot can actually cause it to dissolve some of the pot's surface. Once the water cools, it cannot hold the metal in solution any longer and it precipitates out, oxidizes and forms rust. 
Unlikely to be sewage system remnants ( and even if so, boiling it should have killed any nasty microbes anyway.)

[evan_au]

In the past, with opaque electric kettles, this problem was invisible. But the buildup of deposits on the heating element meant that it took longer to heat the water, and risked burning out the heater element.

With the newer, transparent electric kettles, the problem is much more visible.

We don't have hard water in Sydney, but every few weeks my wife will leave some vinegar water in the kettle overnight, to dissolve the deposits. That seems to work - provided I don't blindly make a cup of tea with the water left in the kettle overnight....

When I lived in Belgium, "hard" water was a real problem. The supermarket sold a variety of products to decalcify kettles, washing machines, irons, etc.

Perhaps the simplest solution is the most dilute: Don't boil the kettle to empty. Tip out the residue in the bottom (which now has concentrated salts), and refill the kettle with fresh water before boiling it again.