Scottish Deep Thoughts

The cold weather has made mornings very cold and, therefore, a fire is necessary to keep from freezing. I started a fire this morning and stocked it up with coal. This made the house heat up quite quickly but also created a problem. I don't quite understand how the water heating system works but it is somehow linked to the fireplace. When the fire is on for a long time it tends to heat the water to an unbelievably hot temperature. I can hear the water boiling when it gets hot enough. Tonight it started to make louder than normal noises. I went to the kitchen to let some of the hot water out of the tank. This is where things get bad...
I turned on the kitchen tap and a bunch of boiling hot water comes out, which soon turned to a muddy black color. Then nothing came out but steam!!
Oh crap.
I run upstairs to my bathroom sink to turn alleviate some more hot water. Same thing: muddy black water! The pipes behind the walls started to clunk and vibrate.
Not good.
I crank open the bath and sink taps, which seemed to have stopped my water pipes and tank from exploding.
I still don't know where the dirty water came from.