Why the two halves want different water
Reprocessed tea is a catch-all name for two quite different things, and the water question is where the difference bites hardest.
Scented tea is a green or white base worked through with flowers. Jasmine is the common example, and osmanthus and magnolia work the same way.
Compressed tea is a dark tea pressed into cakes, bricks or tuo cha. It behaves like dark tea in the cup, because that is what it is.
The scented half wants 85 degrees. The compressed half wants 100. That is a 15 degree gap, and it is the whole category in one line.
Everything else follows from identifying which half you have, so that is the first thing to sort out.
The contrast is sharper here than in any other category, which is why reprocessed tea has a reputation for being unreliable.
Smell the dry tea when the label is unclear. Scented tea smells strongly of flowers before any water touches it, and compressed tea smells earthy or barely of anything.
Scented tea: temperature and water
Eighty-five degrees is the target for jasmine and most other scented teas. The aroma compounds are volatile, and boiling water drives them off.
What is left after a boiling pour is the base tea: a plain green with a faint memory of flowers, which is the usual complaint about jasmine.
Jasmine pearls are rolled rather than loose, release more slowly, and tolerate 90. Use four grams per 150 millilitres for them.
If you cannot tell pearls from loose leaf, look at the shape. Rolled means 90, loose means 85.
Scented teas peak early. The first two steeps carry most of the aroma, and by the fourth you are drinking the base.
Do not rinse the scented half. The aroma sits on the surface of the leaf, and a rinse pours most of it away.
Compressed tea: temperature and water
A full boil is the target for the compressed half, for the same reasons as dark tea: compression and post fermentation.
Use 5 grams in 200 millilitres, a five second rinse discarded first, then steeps of 20 seconds.
Cool or lukewarm water gives you pale liquor and nothing else, and it is the most common way to waste a cake.
Raw pu-erh is the one compressed tea that can turn bitter at a full boil. Keep the steeps short and it stays sweet.
Expect it to improve through the fifth steep. Judging a compressed tea on the first one is like judging a stew by the first spoonful.
When in doubt about a compressed tea, use a full boil. It is the safer of the two defaults.
Check that the kettle actually boils. Many travel and hotel kettles switch off at 90 or below, which is the hidden cause of most flat compressed tea.
Water quality and hardness
Both halves want moderately mineral water, in the same 50 to 150 parts per million range that suits most tea.
The scented half is more sensitive to hardness, because calcium dulls the aroma that is the whole point of the tea.
The compressed half is more tolerant, and slightly harder water actually gives it more body.
Chlorine is a problem for both, and more so for the scented half, where it competes directly with the floral notes.
A carbon filter jug handles chlorine and some hardness. It is the cheapest improvement available to either half.
Minerals and temperature are independent variables, and fixing one will not rescue the other.
Practical takeaway
Identify the tea before you do anything else. Petals in the leaf mean scented, and a pressed shape means compressed.
Set the water from that: 85 for scented, 100 for compressed.
Rinse the compressed half and never the scented half. That asymmetry is the clearest thing about the category.
Keep two vessels if you drink both. One shared pot ends with jasmine flavoured pu-erh.
Store the halves apart. A cake left beside an open tin of jasmine will smell of jasmine within a few weeks.
If a reprocessed tea disappoints you, check whether you identified it correctly before blaming the water or the leaf.
None of this is difficult once the halves are separated. The category only seems unreliable while you are still treating it as one thing.