I know this is a pretty late response, but I myself have been struggling with horribly hard water and being unable to drink light teas (non roasted high quality green Oolong or silver needle white tea). So I’ve been having to try all sorts of things. And I too refuse to buy bottled water just to use for tea.. it’s unconscionable to generate more plastic waste (my Amazon shopping does enough of this).
I find that double boiled water with a touch of baking soda or salt and a drop of lemon juice (per every .5liter) helps the taste. Also always only using cold water from the tap — the coldest it can go. Any hot water added gives even more sediment.
What I do is boil water in a pot on the stove and let the sediment float up. Then I filter it out through the fine synthetic mesh (Primula travel pour over dripper is the best for this — red ring w/ black mesh that goes over a cup; but any super fine material will do).
Also, the kettle makes a huge difference. I’ve tried so many.. but all electric ones with a stainless steel bottom heating plate always make water taste worse for me, but so convenient. However, the best water for me comes out of a glass carafes which are range safe. Though they take a long time and you must be careful. And old INOX stainless steel stove kettles, those always give the best results as opposed to regular stainless. I’d also put aluminum into the same category as INOX, though I don’t have an aluminum pot large enough (aluminum Bialetti moka pots make clean tasting water in my experience, and INOX and aluminum are both non magnetic which may hold some meaning here). I try to keep a pot of boiled water on the stove at all times, however annoying this process is.
And I wash the kettle with vinegar every day. Stainless steel bottom gets white spots from the boiled hard water and the inside of the walls gets a thin layer of deposits (INOX never does). Vinegar dissolved those as well as CLR and leaves no smell or toxins (though, yes, vinegar smells.. but it won’t affect taste of tea and airs out quickly).
I’ve tried filtering water, but no luck so far. My fridge has a nice filter and I try to only fill water from there, but I cannot say it’s any better than cold tap. Brita in my experience doesn’t filter enough to help those with such hard water that they can’t enjoy tea (though there are others, but with very expansive filter replacements that people say leads to fishy taste).
I did just purchase an under the sink water filter that’s connecting directly to the water line (filtered water from the tap, no attachments on the faucet). But I’m yet to install it. I might have to still complete the water boiling ritual... but at least it’ll help some.
Best of luck to anyone who sees this! :)