I've often made the point that water is a very important part of your tea. You just can't make good tea with bad tasting/smelling water. But using good cold water is not enough, as you must warm it so that it remains good. I remember I used to cook my tap water with a stainless steel kettle over my gas heater in my kitchen until I learned gongfu cha with Teaparker. That was all wrong (and I was always disappointed by the tea I made with such water.)
So, how do I boil my water now?
First, I boil it slowly. I use an electric induction heater and use the low to medium speed to bring the water to a slight boil (the well known crab eyes: when air bubbles the size of crab eyes appear in the water). By boiling the water slowly, it's more easy to catch this moment. If you pass it, the water will loose its oxygen and become 'old'.
Second, I use this Japanese iron cast tetsubin pot. The important thing about it is that there is no enamel or glazing inside.Iron, like clay, is a little bit porous. This allows the water to 'breath' and remain young longer. Iron is also quite heavy and heat conductive. This means that the temperature remains hot for quite a long time.
Such an iron pot has another positive characteristic that most people are afraid of: it rusts! See the close up below.
When you use a tetsubin, you can't let the water sit still for several hours (otherwise the water will become brown). You have to use it in a timely fashion and dry it (with heat) at the end of your gongfu cha. Some rust will still appear over time, but the tiny little quantity of iron that dissolves into the water will actually be good for the taste of tea and for your health (especially since you can't eat spinach anymore nowadays!).
I paid over 100 USD for it. Nevertheless, I found that this an investment that pays off as I use it every day, for every tea.